phosphorus and potassium content of commonly...
TRANSCRIPT
PHOSPHORUS AND POTASSIUM CONTENT
OF COMMONLY CONSUMED
MEAT, POULTRY AND FISH PRODUCTS
IN PATIENTS WITH CHRONIC KIDNEY DISEASE
by
Arti Sharma Parpia, RD
A thesis submitted in conformity with the requirements
for the degree of Master of Science
Graduate Department of Nutritional Sciences
University of Toronto
© Copyright by Arti Sharma Parpia (2015)
ii
PHOSPHORUS AND POTASSIUM CONTENT OF COMMONLY
CONSUMED MEAT, POULTRY AND FISH PRODUCTS
IN PATIENTS WITH CHRONIC KIDNEY DISEASE
Arti Sharma Parpia
Master of Science
Department of Nutritional Sciences
University of Toronto
2015
ABSTRACT
Patients with chronic kidney disease (CKD) are advised to limit their intake of phosphorus and
potassium, yet there is uncertainty concerning the actual content of these minerals in the
Canadian food supply. In order to gain insight into the contribution of food additives to
phosphorus and potassium intake, we chemically analyzed phosphorus, potassium, sodium and
protein content of commonly consumed meat, poultry and fish (MPF) products. A food
frequency questionnaire administered to patients receiving dialysis (n=67) identified unbreaded
chicken, ground beef, steak, white fish, beef burgers, deli ham, shrimp and bacon as commonly
consumed MPF. Phosphorus and potassium content was significantly (P<0.05) higher in MPF
with versus without additives listed on ingredient list. Sodium-reduced MPF had significantly
(p<0.001) higher amounts of potassium from additives compared to original non-sodium reduced
counterparts. The use of additives in packaged MPF products significantly contribute to the
phosphorus and potassium loads in patients with CKD.
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ACKNOWLEDGMENTS
I would first like to thank my thesis supervisor, Dr. Pauline Darling, for her endless
support and guidance throughout the completion of my Master’s degree. I have learned an
invaluable amount from her expertise and methodical approach to research and am extremely
grateful for her dedication and generous time commitment to this study.
I am very appreciative of my committee members, Dr. Mary L’Abbé, Dr. Marc
Goldstein, Dr. Joanne Arcand and Dr. Berna Magnuson for the expert skill and knowledge they
each possess in their respective fields. Committee meetings were always a positive experience
due to their encouragement, helpful feedback and indispensable contributions.
I would like to recognize St. Michael’s Hospital for their assistance in this achievement,
as well as my colleagues at work. Particularly, Pamela Robinson and Jill Campbell for their
support in accomplishing my academic goals while working full time. My sincere thanks to my
dietitian colleagues; Carol Huang, Karen Burleigh, Alyson Martinez, Laura O’Brien and Dana
Whitham, for their sound advice and aid with the recruitment of patients. I am grateful for my
colleagues in hemodialysis and office mates who provided a listening ear when I needed it most.
Lastly, I would like to acknowledge and thank the patients that voluntarily took part in the study
and who inspire me with their perseverance in more ways than they know.
I am indebted to my wonderful family and friends for always being there for me. To my
husband, Sameer Parpia, whose own determination and diligent work ethic was my motivation to
do the same. From cooking meats with me for endless hours, providing statistical advice and
being a source of unwavering encouragement, the success of my masters would not have been
possible without his help and reassurance. Lastly, I would like to dedicate this thesis to my
parents for always supporting me in every way possible to ensure the success of my goals and
aspirations.
This research was funded and supported by a grant from the
Canadian Foundation for Dietetic Research.
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TABLE OF CONTENTS
ACKNOWLEDGMENTS .................................................................................................................... iii
LIST OF TABLES ............................................................................................................................ vii
LIST OF FIGURES ......................................................................................................................... viii
LIST OF APPENDICES ..................................................................................................................... ix
LIST OF COMMON ABBREVIATIONS ............................................................................................... x
1.0 Introduction ............................................................................................................................. 1
2.0 Literature Review ................................................................................................................... 3
2.1 Chronic Kidney Disease ....................................................................................................... 3
2.2 Nutritional considerations in chronic kidney disease ........................................................... 4
2.2.1 Protein-energy malnutrition and its complications in chronic kidney disease .......... 4
2.2.1.2 Dietary protein requirements ...................................................................... 4
2.2.1.2.1 Protein food sources ..................................................................... 5
2.2.2 Phosphorus, hyperphosphatemia and its complications in chronic kidney disease ... 5
2.2.2.1 Dietary phosphorus restriction ................................................................... 7
2.2.2.1.1 Phosphorus food sources .............................................................. 7
2.2.2.1.2 Phosphorus additives in foods ..................................................... 8
2.2.2.2 Phosphorus labelling regulations in Canada ........................................... 11
2.2.2.3 Phosphorus labelling regulations in United States .................................. 12
2.2.3 Potassium, hyperkalemia and its complications in chronic kidney disease ............. 13
2.2.3.1 Dietary potassium restriction ................................................................... 13
2.2.3.1.1 Food sources of potassium ......................................................... 14
2.2.3.1.2 Potassium additives in foods ...................................................... 15
2.2.3.2 Potassium labelling regulations in Canada .............................................. 16
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2.2.3.3 Potassium labelling regulations in United States ..................................... 17
2.2.4 High sodium intake and its complications in chronic kidney disease ..................... 18
2.2.4.1 Dietary sodium restriction ........................................................................ 19
2.2.4.1.1 Food sources of sodium ............................................................. 19
2.3 Sodium reduction in Canada .............................................................................................. 20
2.3.1 Sodium Working Group ........................................................................................... 20
2.3.2 Strategies to reduce sodium in meat, poultry and fish products .............................. 21
2.3.2.1 Use of potassium additives in sodium reduction of foods ......................... 22
2.3.2.2 Use of phosphorus additives in sodium reduction of foods ...................... 23
3.0 Rationale and Objectives ...................................................................................................... 25
4.0 Commonly consumed meat, poultry and fish products among patients with End-
Stage Renal Disease at a Tertiary Care Teaching Hospital in Toronto, Canada: Food
Questionnaire.......................................................................................................................... 28
4.1 Introduction ........................................................................................................................ 28
4.2 Materials and Methods ....................................................................................................... 29
4.2.1 Design ...................................................................................................................... 29
4.2.2 Patient questionnaire development .......................................................................... 29
4.2.3 Face validation of patient questionnaire .................................................................. 30
4.2.4 Eligibility criteria ..................................................................................................... 30
4.2.5 Recruitment methods ............................................................................................... 31
4.2.6 Questionnaire administration and data collection .................................................... 31
4.2.7 Data analysis ............................................................................................................ 31
Results 4.4 ................................................................................................................................ 32
4.4.1 Participant recruitment ............................................................................................. 32
4.4.2 Demographic and clinical characteristics of participants ........................................ 32
4.4.3 Commonly consumed meat, fish and poultry products ........................................... 33
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4.4.4 Purchasing and preparation behaviours ................................................................... 33
4.4.5 Self-reported adherence to renal diet restrictions .................................................... 33
4.5 Discussion .......................................................................................................................... 43
4.5.1 Conclusions .............................................................................................................. 45
5.0 Phosphorus and potassium content of commonly consumed meat, poultry and fish
products among patients with CKD ..................................................................................... 46
5.1 Introduction ........................................................................................................................ 46
5.2 Materials and Methods ....................................................................................................... 47
5.3 Results ................................................................................................................................ 49
5.4 Discussion .......................................................................................................................... 57
6.0 Do Sodium Reduced Meat and Poultry Products Contain a Significant Amount of
Potassium and Phosphorus from Additives? ....................................................................... 61
6.1 Introduction ........................................................................................................................ 61
6.2 Materials and Methods ....................................................................................................... 62
6.3 Results ................................................................................................................................ 64
6.4 Discussion .......................................................................................................................... 70
7.0 Overall Discussion & Conclusions ....................................................................................... 73
7.1 Study Implications for Practice and Future Studies ........................................................... 76
REFERENCES ................................................................................................................................. 78
APPENDICES .................................................................................................................................. 93
vii
LIST OF TABLES
Table 2.1 Classification of stages of chronic kidney disease ………………………………..3
Table 2.2 Summary of studies examining phosphorus content by chemical analysis
in foods with and without phosphorus additives listed on the product label….....10
Table 4.1 Demographic and clinical characteristics of participants.…...…………………..35
Table 4.2 Ranked Consumption of meat, poultry and fish products based on
estimated weight (g) consumption per month by ESRD patients….………...…..37
Table 4.3 Ranked Sources of meat, poultry and fish products, based on
number of servings consumed per month by ESRD patients.………....…………39
Table 4.4 Purchasing, food preparation behaviours and self-reported adherence
to renal diet restrictions…….………………………….…………...…………….40
Table 4.5 Characteristics of study patients receiving hemodialysis as compared with
the Canadian Institute for Health Information data………..…………………….42
Table 4.6 Characteristics of study patients receiving peritoneal dialysis as compared
with the Canadian Institute for Health Information data…………………...……42
Table 5.1 Meat, poultry and fish food categories and comparable reference foods…..……51
Table 5.2 Characteristics of meat, poultry and fish (MPF) products commonly
consumed by patients with chronic kidney disease…………..………………….52
Table 5.3 Comparison of analyzed nutrient content among MPF categories containing
phosphorus additives, without phosphorus additives and reference foods….…...54
Table 5.4 Analyzed nutrient content of MPF categories with and without phosphorus
additives listed on the ingredient list and reference foods...……………………..55
Table 5.5 Comparison of analyzed nutrient content among chicken products labelled
seasoned, products not labelled seasoned and reference products………………56
Table 5.6 Comparison of analyzed nutrient content among MPF categories containing
potassium additives, not containing potassium additives and reference foods..…56
Table 6.1 Comparison of analyzed nutrient levels in paired sodium reduced and original
(non-sodium reduced) meat and poultry products………...……….........……….65
Table 6.2 Comparison of sodium reduced, original (non-sodium reduced), and
reference meat and poultry products……………………………………….…….66
Table 6.3 Chemical analysis of sodium, potassium, phosphorus and protein content of
paired original (non-sodium reduced) and sodium-reduced meat and poultry
products…………………………………………………………………………..67
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LIST OF FIGURES
Figure 4.1 Flow diagram of subject recruitment and study completion……………………..34
Figure 5.1 Percent of MPF foods containing phosphorus additives on the ingredient list
according to MPF category……………………………………………………....53
Figure 6.1 Presence and type of additives in original and sodium reduced meat and
poultry products (MPP)…………………………………………………………..69
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LIST OF APPENDICES
Appendix A Food questionnaire…………..…………………………………………………..93
Appendix B Face validation recruitment pre-amble……...………………………………….119
Appendix C Recruitment pre-amble…………………………………………..……………...122
Appendix D Patient consent form…………………………………………….……………...125
Appendix E Data collection form…………………………………………..………………...129
Appendix F Comparison of store brands and national brands among major subgroups
of MPF foods...…………………………………...…………………………….131
Appendix G Comparison of analyzed nutrient content among processed and minimally
processed foods………………...……………………………………………….133
Appendix H Comparison of analyzed nutrient content among breaded chicken products…...135
Appendix I The accuracy of Canadian Nutrient File data for reporting phosphorus, potassium,
sodium and protein in commonly consumed MPF products………...…………137
x
LIST OF COMMON ABBREVIATIONS
CFIA Canadian Food Inspection Agency
CKD Chronic Kidney Disease
CNF Canadian Nutrient File
CVD Cardiovascular Disease
ESRD End-Stage Renal Disease
FDA Food and Drug Administration
K Potassium
K/DOQI Kidney Disease Outcome Quality Initiative
KDIGO Kidney Disease: Improving Global Outcomes
MPF Meat, Fish and Poultry
MPP Meat and Poultry Products
Na Sodium
NFt Nutrition Facts Table
P Phosphorus
PEM Protein Energy Malnutrition
Pro Protein
SMH St. Michael’s Hospital
USDA United States Department of Agriculture
1
1.0 Introduction
Chronic kidney disease (CKD) is increasingly prevalent and associated with high
morbidity and mortality (Kovesdy et al, 2006). The progressive decline in kidney function leads
to the retention of substances, such as phosphorus, potassium and sodium, and is associated with
adverse outcomes (Kopple & Massry, 2004). High serum phosphorus levels have been
independently associated with increased cardiovascular mortality, while a high potassium
concentration can lead to fatal cardiac arrhythmias (Putcha & Allon, 2007; Palmer et al, 2011).
Dietary approaches aim to address these abnormalities by dietary restriction of these nutrients in
the diet of patients with CKD.
In 2010, the Sodium Working Group was established to develop a population health
strategy to lower the dietary sodium intake of Canadians and has set a 2016 interim goal for
mean population consumption of sodium at 2300 mg per day. A pillar of the sodium reduction
strategy was the voluntary reduction of sodium levels in packaged foods (Health Canada, 2010).
Sodium plays a key role in the microbial safety and the flavor profile in many foods including
meat, poultry and fish products (Doyle & Glass, 2010). Hence, replacement of sodium or salt
with a sodium analogue that provides similar functional effects is often required. One of the
many ways food manufacturers can reduce sodium levels in meat, poultry and fish food items is
to replace the sodium with additives such as potassium additives or phosphorus additives
(Desmond, 2006).
In recent years, phosphorus additives have been identified as a significant contributor to
dietary phosphorus intake (Carrigan et al, 2014; Leon et al, 2013; Bell et al, 1977). Phosphorus
additives are found in a wide variety of foods, and can provide favorable effects, such as
improving texture and shelf-stability (Lampila, 2013). However, these additives are almost
entirely bioavailable and can contribute to elevated serum phosphorus levels (Calvo et al, 2014).
Potassium additives provide a salty flavor, and potassium chloride is the most frequently
used replacement for sodium chloride (table salt) (CTAC, 2009). However, the use of potassium
salts has been associated with toxicity in patients with impaired renal handling of potassium
(Doorenbos & Vermeij, 2003). Additional additives, such as potassium lactate and potassium
2
phosphates, may also be used in the sodium reduction of foods but there are few studies
describing the potassium content of foods with additives.
The potassium and phosphorus contents in foods are not listed on the nutrition facts table.
Therefore, it is difficult to determine the contribution of phosphorus and potassium additives to
the levels of nutrients in foods. Furthermore, studies have demonstrated that nutrient databases
often underestimate the phosphorus content in foods with additives (Sullivan et al, 2007).
Accurately estimating the phosphorus and potassium content in foods is crucial in order for
clinicians to make proper dietary recommendations for patients with CKD and for patients to
choose appropriate foods in accordance with their renal diet. This in turn may help prevent
hyperphosphatemia, hyperkalemia and their respective complications.
Dietary protein requirements are increased in patients with end-stage renal disease who
are receiving dialysis treatment. Given that meat, poultry and fish products represent rich sources
of dietary protein, these patients are encouraged to increase their intake of these products. In
addition to a high protein diet, these patients also require a low sodium diet of less than 2000 mg
per day (Kidney Disease: Improving Global Outcome (KDIGO), 2012). This creates additional
concern as patients are educated to read labels and choose low sodium food products
(Vennegoor, 2009), which may unintentionally lead to an increased intake of phosphorus and
potassium.
Thus, the overall aim of this dissertation is to enhance knowledge of the amounts of
phosphorus, potassium and protein content in commonly consumed meat, poultry and fish
products among the CKD population, and to determine whether the sodium reduction of these
foods is associated with increased use of phosphorus and potassium additives.
3
2.0 Literature Review
2.1 Chronic Kidney Disease
Chronic kidney disease (CKD) is defined as ‘abnormalities of kidney structure or
function, present for at least 3 months, with implications for health’ (KDIGO, 2012). There is a
high prevalence of CKD in Canada as it is estimated to affect approximately 3 million Canadians
(Arora et al, 2013). Leading risk factors for CKD include diabetes mellitus and hypertension.
The estimated glomerular filtration rate is a common measure of kidney function and is
used to establish the five progressive stages of kidney disease (Levey et al. 2011) (See Table
2.1). Generally, symptoms and complications of CKD are not seen until the later stages of kidney
disease. Once the estimated glomerular filtration rate falls below 15 mL/min/1.73m2, the patient
is considered to be at Stage 5 kidney disease or end-stage renal disease (ESRD), wherein he/she
will require a form of renal replacement therapy. The two types of renal replacement therapy are
a kidney transplant or dialysis. Dialysis is a treatment that purifies blood and the two main forms
are hemodialysis and peritoneal dialysis. In 2012, over 40,000 Canadians received renal
replacement therapy, which is a 40% increase from 2003. More specifically, 58% were receiving
dialysis therapy and the remaining 42% had a functioning kidney transplant (Canadian Organ
Replacement Register (CORR), 2014).
As the kidneys are vital organs responsible for the filtration of blood, removal of waste
products and production of hormones, the progressive deterioration of kidney function leads to
many health complications. Furthermore, CKD is associated with a significant increased risk of
cardiovascular and all-cause mortality (Rosenberg, 2014).
Table 2.1 Classification of stages of chronic kidney disease
GFR Stage GFR (mL/min per 1.73 m2) Relative kidney function
1 >90 High or optimal
2 60-89 Mildly decreased
3a 45-59 Mildly to moderate decreased
3b 30-44 Moderately to severely decreased
4 15-29 Severely decreased
5 <15 Kidney failure or end-stage renal disease
Adapted from KDIGO 2012: Practice Guidelines for the Evaluation and Management of CKD
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2.2 Nutritional considerations in chronic kidney disease
As CKD progresses, there is decreased renal clearance of solutes, including sodium,
potassium, phosphorus and water, which leads to the retention of these nutrients in the body. In
addition, decreased gastrointestinal absorption of nutrients, such as calcium and vitamins, can
contribute to deficiencies (Kopple & Massry, 2004). Furthermore, there are increased losses of
amino acids, protein and water-soluble vitamins during dialysis therapy itself (Ikizler et al,
1994). As a result, patients with CKD, who have varying levels of kidney function, multiple
comorbidities and different dietary intake patterns, require individualized dietary modifications
to compensate for the many factors that affect nutritional status.
2.2.1 Protein-energy malnutrition and its complications in chronic kidney disease
CKD can lead to metabolic acidosis, persistent inflammation and increased
glucocortocoid activity, all of which can lead to increased protein catabolism. In addition,
patients on dialysis have increased amino acid losses during dialysis, thus further increasing their
protein needs (Carrero et al, 2013). In combination with factors such as loss of appetite,
increased energy expenditure, decreased anabolism and comorbidities, patients with CKD are at
a high risk of developing protein-energy malnutrition (PEM) (Carrero et al, 2013).
The prevalence of PEM among patients with CKD is high, varying from 18-75% across
studies (Foque et al, 2008). While the majority of patients have a mild to moderate forms of
PEM, approximately 10% of patients have a severe form (Kuhlmann et al, 2007). Studies have
shown that there is a strong association with PEM and increased morbidity and mortality in
patients with CKD (Kalantar-Zadeh et al, 2004). Therefore a cornerstone of nutrition therapy in
renal disease involves the prevention and treatment of PEM. Strategies may include the use of
oral nutritional supplements, changes in the dialysis prescription to stimulate appetite, and
optimizing dietary protein and energy intake at meals and snacks.
2.2.1.2 Dietary protein requirements
The 2012 Kidney Disease, Improving Global Outcomes (KDIGO) clinical practice
guidelines for the evaluation and management of CKD (KDIGO, 2012) suggest a protein intake
of 0.8 g/kg/day, with avoidance of high protein intakes (>1.3 g/kg/day) in adults who are not on
dialysis with a GFR <30 mL/min/1.73m2 (Stage 4 and 5). The KDIGO work group concluded
5
that a low dietary protein intake (< 0.8 g/kg/d) did not offer an advantage in the progression of
kidney disease, while excess dietary protein leads to the accumulation of uremic toxins in later
stages of CKD.
In contrast, once a patient’s kidney disease has progressed to a point where they require
dialysis therapy, protein requirements increase due to losses of protein during the dialysis
procedure and greater protein catabolism in end stage renal disease. The Kidney Disease
Outcomes Quality Initiative (K/DOQI, 2000) clinical practice guidelines for protein intake for
chronic dialysis patients suggest that patients receiving hemodialysis consume 1.2 g/kg/day,
while patients receiving peritoneal dialysis ingest 1.2-1.3 g/kg/day of protein. This is because
patients receiving peritoneal dialysis have increased protein losses compared with those on
hemodialysis. These recommendations were determined by several nitrogen balance studies, as
this was considered the classical method to determine dietary protein requirements (Kopple,
2001; Food & Nutrition Board, 1989). However, many of these studies were small and contained
methodological limitations, such as short study durations, variations in hemodialysis treatments,
and included patients with acute superimposed illnesses and/or PEM (Kopple, 2001).
2.2.1.2.1 Protein food sources
A qualifying statement included in the K/DOQI protein intake guidelines states that “at
least 50% of the dietary protein should be of high biological value”. A food that is high in
protein quality refers to a protein that has similar amino acid profile to human protein and is
efficiently utilized by the body (K/DOQI, 2000). Dietary protein sources that are high in protein
quality are generally sources of animal protein such as meat, poultry, fish, eggs and dairy (Jadeja
& Kher, 2012). Plant sources of protein that are also high in protein quality include soy, legumes,
nuts and seeds, but these foods contain a high amount of potassium and phosphorus and
consumption is generally limited in a renal diet (Kalantar-Zadeh et al, 2010).
2.2.2 Phosphorus, hyperphosphatemia and its complications in chronic kidney disease
Phosphorus is a non-metal element essential for normal cell function in all living
organisms as it is a component of phospholipids, nucleic acids and adenosine triphosphate
(Knochel, 2006). Phosphorus is mostly found in the bones and teeth, however ~1% is found in
extracellular fluid and blood and is tightly regulated by the parathyroid hormone and fibroblast
growth factor (IOM, 1997). After intestinal phosphorus absorption, excess dietary phosphorus is
6
mainly excreted through the kidneys where phosphorus is filtered at the glomerulus and
reabsorbed in the proximal tubule in order to maintain serum phosphorus levels within the
normal range (Kalantar-Zadeh et al, 2010).
Hyperphosphatemia, or elevated serum phosphorus concentration above the normal range
(0.85-1.45 mmol/L), is a common condition in persons with CKD. It is associated with numerous
conditions such as extraskeletal calcification, renal osteodystrophy and secondary
hyperparathyroidism (Palmer et al, 2007; Albaaj et al, 2003; Friedman et al, 2005; Tomiyama et
al, 2006). In addition, hyperphosphatemia is associated with an increased risk of mortality in
individuals with advanced stages of CKD (Block et al, 1998; Kestenbaum et al, 2005; Palmer et
al, 2011). Remarkably, recent studies conducted in the general population have even shown an
association between higher serum phosphorus levels and/or higher dietary phosphorus intake and
adverse cardiovascular outcomes (Dhingra et al, 2007; Tonelli et al, 2005; Chang et al, 2014).
While the exact mechanism is not clear, it is thought that in the presence of secondary
hyperparathyroidism, calcium phosphate precipitation leads to vascular calcification and a
subsequent increase in cardiovascular disease, which is the leading cause of death in CKD
(Kendrick & Chonchol, 2011). Despite this strong association and plausible mechanism, it is
important to note that there have been no randomized clinical trials to date showing that lowering
serum phosphorus concentration results in a reduction in mortality (Navaneethan et al, 2009;
Palmer et al, 2007; Strippoli et al, 2006).
Interventions aimed at controlling serum phosphorus levels include reducing intestinal
absorption with phosphorus binding medication, removing phosphorus with dialysis therapy, and
dietary phosphorus restriction. The pill burden of dialysis patients has been shown to be the
highest of any chronic disease states, and phosphate binding medication can contribute up to half
of the daily pill burden. There is a high reported non-adherence rate to phosphate binder
medication of approximately 60% (Chiu et al. 2009). Moreover, phosphorus removal during
dialysis therapy is also limited to 2100-2700 mg per week (Kuhlmann, 2010). Therefore,
modification of the dietary phosphorus load plays a crucial role in the normalization of serum
phosphorus levels in CKD.
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2.2.2.1 Dietary phosphorus restriction
As per the K/DOQI clinical practice guidelines for bone metabolism and disease in CKD
(2003), patients with hyperphosphatemia are advised to restrict their dietary intake of phosphorus
to between 800 and 1000 mg per day. K/DOQI recommends that patients with stage 3 and 4
CKD maintain their serum phosphorus levels between 0.87 and 1.49 mmol/L, while stage 5
patients with CKD maintain a phosphorus level less than 1.78 mmol/L. While evidence suggests
that educating patients about dietary phosphorus restriction decreases serum phosphorus levels
(Caldeira et al, 2011), there are no randomized controlled trials showing that dietary phosphorus
restriction leads to improved cardiovascular outcomes. Hence, the more recent KDIGO clinical
practice guidelines for bone mineral disorders (2009) suggest that dietary phosphorus intake be
limited, but that there was insufficient data to prescribe a dietary phosphorus restriction as the
primary intervention in the management of hyperphosphatemia. In addition, the KDIGO authors
did not provide any specific guidance on dietary phosphorus amount that should be ingested,
likely due to lack of evidence. Further studies may help to establish more specific
recommendations regarding the daily dietary phosphorus intake in patients with CKD.
2.2.2.1.1 Phosphorus food sources
According to the NHANES 2005-2006 survey of the general US population, men
between the ages of 19-50 consumed more than 1600 mg phosphorus per day, while women of
the same age consumed over 1100 mg phosphorus per day (Calvo & Uribarri, 2013). About 20-
30% of the dietary phosphorus intake in the general population comes from meat, fish, poultry,
milk and eggs (Calvo & Park, 1996). Since animal products are a significant source of
phosphorus, there is a close association between phosphorus and the protein content of food
(Boaz and Smetana, 1996). Although the K/DOQI guidelines (2000) recommend increased
protein intake for patients with ESRD on dialysis (1.2 g/kg/day), evidence suggests that a diet
with this protein level will lead to hyperphosphatemia in patients on dialysis (Uribarri & Calvo,
2003). Paradoxically, Shinaberger et al (2008) showed that participants who had a fall in serum
phosphorus concentration and had a low dietary protein intake were at increased risk of death,
presumably related to protein wasting and malnutrition. Patients whose protein intake increased
while their serum phosphorus declined showed the greatest survival benefit, possibly because
this mitigates the mortality risk associated with hyperphosphatemia and PEM. The K/DOQI
guidelines (2003) have suggested choosing foods with a low phosphorus to protein ratio as it
8
focuses on both lowering dietary phosphorus intake as well as ensuring sufficient protein intake
to optimize nutritional status of patients with CKD, and is independent of serving size.
Other dietary sources of phosphorus include whole grains, legumes, nuts and dairy
products. The bioavailability of organic phosphorus, from animal sources and plant sources, is
approximately 40-60%, with phosphorus from animal sources more effectively absorbed than
plant sources (Uribarri, 2007; Calvo et al, 2014). Phosphorus from plant-based proteins have
lower digestibility as they are in the storage form of phytate. Since most mammals lack the
enzyme phytase, only 20-50% of phosphorus from nuts, legumes and grains are absorbed in the
gastrointestinal tract. Moe et al (2011) conducted a crossover trial with nine pre-dialysis CKD
patients who consumed one week of a vegetarian diet or meat diet containing equivalent amounts
of phosphorus. The results demonstrated the group consuming a vegetarian diet had lower serum
phosphorus levels than the meat diet group, indicating that the source of dietary phosphorus is an
important factor in determining serum phosphorus concentrations.
2.2.2.1.2 Phosphorus additives in foods
Inorganic sources of phosphorus require no enzymatic digestion, and are easily and
rapidly absorbed with a bioavailability of 80-100% (Calvo et al, 2014). Sources of inorganic
phosphorus include processed foods, such as restructured meats, processed cheeses, instant
products (puddings), refrigerated bakery products and certain beverages as they often contain
phosphorus additives. Phosphorus additives are used by food manufacturers for their ability to
extend shelf-life, improve colour, retain moisture, emulsifying properties and as a leavening and
anti-caking agent (Kalantar-Zadeh et al, 2010).
Adherence to a dietary phosphorus restriction has become increasingly difficult due to the
addition of phosphorus additives to food, which was reported to contribute up to 1000 mg
phosphorus/day to the average American diet (Bell et al, 1977; Uribarri and Calvo, 2003). A
recent unpublished study in Ontario scanned the package labels of meat, poultry and fish (MPF)
products in grocery stores in the Waterloo region. The authors reported that 43% of packaged
meat products had a phosphorus additive listed on the ingredient list (Cafferty et al, 2014
abstract). More specifically, deli meats had the highest prevalence of phosphorus additives on the
ingredients list (78.3%), followed by frozen fish (60.4 %) and frozen chicken products (57.3%).
Studies reporting the chemical analysis of packaged foods in the United States (U.S.) and Europe
9
showed that the addition of phosphorus additives significantly increases the phosphorus content
of the food items by as much as 66% (see Table 2.2). To our knowledge, no such studies have
taken place in Canada.
U.S. studies have demonstrated a high variability in the use of phosphorus additives in
the food supply, and have shown that the United States Department of Agriculture (USDA)
national nutrient database underestimates the phosphorus content of foods which contain
additives (Sullivan et al, 2007). It is therefore not usually clear to the consumer that such
products may have elevated amounts of phosphorus. Bell et al. (1977) completed a crossover
trial in which 8 healthy volunteers were fed two isocaloric diets; one with additives and one
without phosphorus additives. The high phosphorus additive diet led to increased serum
phosphorus levels and urinary phosphorus excretion. Thus, the wide array of food sources
containing phosphorus additives can contribute to hyperphosphatemia in patients with CKD and
result in difficulties maintaining a lower phosphorus intake level (Sherman and Mehta, 2009a).
In Canada, phosphorus content is usually not listed on Nutrition Fact tables, adding to the
difficulty of estimating phosphorus content of foods with additives. Currently, patients are
educated to avoid foods with a phosphorus additive listed on the ingredient list (ORN, 2013).
Reading ingredient lists can be an arduous task for patients with CKD and eliminating all foods
listing a phosphorus additive can greatly limit food choices. However, a randomized controlled
trial was conducted by Sullivan et al. (2009) in which the intervention group received education
to read the ingredients list and avoid foods that listed a phosphorus additive, while the control
group received usual care. The results indicated that patients educated to avoid phosphorus
containing food additives resulted in modest (0.2 mmol/L), but significant decreases in serum
phosphorus levels.
10
Table 2.2 Summary of studies examining phosphorus content by chemical analysis in foods with
and without phosphorus additives listed on the product label
Author
Year
Country
Method Key Findings
Lou-Arnal et al.
2014
Spain
118 various types of processed
foods
Higher P content and P:Pro ratio
in foods with P Additives (P
content varies per food group)
Carrigan et al.
2014
United States
Low additive vs. additive
enhanced diet (4-day)
60% higher P content in additive
enhanced diet
Léon et al.
2013
United States
56 top selling grocery items with
and without P additives
4-day sample meals with and
without P additives
60% more P in top-selling foods
with P additives
70% higher P content in sample
meals with P additives
Cupisti et al.
Nov 2012
Italy
40 samples of ham with and
without P additives
Measured inorganic P content
66% more inorganic phosphorus
in ham with P additives
Benini et al.
2011
Italy
60 samples of cooked ham, roast
turkey breast and roast chicken
breast with and without P
additives
57% higher total P content in
food items with P additives
Sherman et al.
2009a
United States
36 uncooked enhanced* products
and unenhanced meat and
poultry products
28% higher P:Pro ratio in food
items enhanced with P additives
Sherman et al.
2009b
United States
44 meat, poultry and fish
products with and without
phosphorus additives
62% higher P:Pro ratio in food
items with P additives
Sullivan et al.
2007
United States
38 chicken products with and
without P additives
Chicken with P additives
significantly increase the amount
of P in products.
USDA nutrient database
underestimates P content of
foods with P additives
Abbreviations: P = Phosphorus; Pro = Protein; USDA = United States Department of Agriculture
11
2.2.2.2 Phosphorus labelling regulations in Canada
It is not mandatory to report the phosphorus content of foods on the Nutrition Facts table
(NFt) in Canada. When voluntarily displaying phosphorus content, it is depicted as a percentage
of the daily value, and not it milligrams. The daily value for phosphorus represents the percent
amount of phosphorus that a serving of food provides, based on the recommended daily intake of
1100 mg/day (CFIA, 2015a). Hence, consumers generally do not know the amount of
phosphorus that is in a particular food item and if it is listed on the NFt, it is in the form of a
percent of daily value, which may be difficult to interpret. In addition, Health Canada has
recently proposed for the daily value of phosphorus to be based on the increased reference intake
of 1250 mg/day (Health Canada, 2015a).
In Canada, compositional standards in both the Food and Drug Regulations (FDR) and
the Meat Ingredient Regulations (MIR) allow for the addition of phosphate salts and/or water to
meats, including solid cut meat products (i.e. pork roasts), chopped and formed meat products
(i.e. ground meat) and prepared meat products (i.e. sausages) (CFIA, 2013). These solutions are
added or injected into meat and poultry products to help enhance moisture in meat products,
reduce purge, and increase shelf-life (Murphy-Gutekunst, 2005). According to Canadian food
labelling regulations (CFIA, 2013), the term “seasoned” is used when phosphate salts or spices
with water are injected or incorporated into the “solid cut” meat product (i.e. “seasoned chicken
breast”). The total maximum level of phosphate salts that can be added to MPF products is 0.5%
by weight, calculated as sodium phosphate dibasic added to the product (CFIA, 2013). The
contribution of phosphorus at 0.5% by weight varies based on the type of phosphate salt used,
but can range from approximately 100-150 mg phosphorus per 100 grams of MPF. Phosphate
salts, such as sodium phosphate, must be declared on the list of ingredients on both plant packed
and retail packed solid cut meats. Exemptions to this rule include side bacon, Wiltshire bacon,
pork jowls and salt beef. In addition, unpackaged meat items that are sold behind a meat or deli
counter and cured products (i.e. ham) that are packed at retail, are not required to labelled (CFIA,
2013).
If phosphorus additives are used, they must be declared in the ingredients list of pre-
packaged products, however, they do not need to be quantified and listed by weight of the
product. Also, if the product contains more than one phosphorus additive, it can be collectively
12
listed as “sodium phosphates” (CFIA, 2015b). Common phosphorus additives that are used in
meat products include, disodium phosphate, potassium phosphate, sodium acid pyrophosphate
and tetrasodium pyrophosphate (CFIA, 2015b).
2.2.2.3 Phosphorus labelling regulations in United States
Similar to Canadian regulations, the phosphorus content is not required to be listed on the
Nutrition Facts label in the U.S. If manufacturers voluntarily disclose phosphorus content, it is
also displayed as a percentage of daily value. The daily value in the U.S. is 1000 mg phosphorus
per day, which is slightly lower than the Canadian daily value. However, the U.S., like Canada,
has proposed an increase in the daily value to 1250 mg/day (FDA, 2014c).
Phosphorus additives are categorized as foods additives considered to be ‘generally
recognized as safe (GRAS)’. The term GRAS indicates that the ingredient or additive is not
known to have harmful effects under prescribed conditions of use. These products are exempted
from FDA’s testing and approval process for food additive use (USDA, 2007). As of 2009,
eleven phosphate salts were approved for use in meat products in the U.S., five of which were
potassium salts (Sherman and Mehta, 2009b).
According to Food Safety and Inspection Service (FSIS, 2015) phosphorus additives,
including potassium phosphates, can be added or injected in amounts that total up to 0.5% of the
product formula of meat and poultry products. Fish and seafood falls under the regulations of the
Food and Drug Administration (FDA), which allow sodium phosphate to be included according
to good manufacturing practice (FDA, 2014b). Good manufacturing practice (GMP) specifies
that the “quantity of the ingredients added to food does not exceed the amount reasonably
required to accomplish the intended physical, nutritional, or other technical effect in food” (FDA,
2014a). Hence, unlike Canada, there is no maximum limit specified for the amount of sodium
phosphate added to fish and seafood products in the U.S.
Phosphorus additives must be listed on the ingredient list, and if there is more than one
sodium phosphate in the food item, it can be collectively listed as sodium phosphates (USDA,
2010). Similarly, ‘potassium phosphates’ is the collective name that can be used for more than
one potassium phosphate.
13
Typically, the term ‘enhanced’ is used for a meat or poultry product that has been
injected with a solution that may contain phosphate salts. However, FSIS (2014) recently issued
a new rule which will prohibit the use of the term enhanced effective January 1st, 2016. New
labeling will include a phrase declaring the product “contains x% solution”, as well as providing
individual ingredients of the solution listed in descending order by weight.
2.2.3 Potassium, hyperkalemia and its complications in chronic kidney disease
Potassium is the most abundant intracellular cation in the body, with 98% of potassium
contained inside the cells and only 2% in the extracellular compartment (Putcha & Allon, 2007).
Small changes in extracellular or serum potassium concentrations can affect neural transmission,
muscle contraction and vascular tone (IOM, 2005). In individuals with normal kidney function,
90-95% of dietary potassium is excreted through the kidneys, while the remaining amount is
excreted in the stool (Putcha & Allon, 2007). Potassium is easily filtered by the glomerulus and
the majority of filtered potassium is reabsorbed in the proximal tubule and loop of Henle
(Palmer, 2014). As the kidneys are largely responsible for the excretion of potassium, patients
with CKD are at a greater risk of developing hyperkalemia.
Hyperkalemia is defined as a serum potassium level that is greater or equal to 5.5 mmol/L
(Jamison, 2001). If serum potassium concentration increases to high levels, it can lead to cardiac
arrhythmias. Furthermore, sudden cardiac death is the most common cause of death in patients
on hemodialysis, and it is often caused by fatal arrhythmias (Sanghavi et al, 2013).
Hyperkalemia occurs frequently in patients with chronic kidney disease (CKD) as they have a
decreased ability to excrete potassium through their kidneys. There are many causes of
hyperkalemia which include, but are not limited to, inadequate dialytic potassium removal,
medications that reduce urinary potassium excretion, insulin deficiency, metabolic acidosis,
severe constipation and excess dietary intake of potassium (Putcha & Allon, 2007).
2.2.3.1 Dietary potassium restriction
The recommended daily intake of potassium for an individual with moderate to severe
kidney disease is 2000-3000 mg/day (Nelms et al 2007) or 1 mmol (39 mg)/kg of ideal body
weight (Byham-Gray & Wiesen, 2005; ADA & DC, 2000). This is significantly lower than the
Adequate Intake (AI), which recommends 4700 mg/day in the general population (IOM, 2005).
The AI is based on the Dietary Approaches to Stop Hypertension (DASH) diet study which
14
demonstrated that along with a low sodium diet, a high intake of dietary potassium from sources
such as fruits, vegetables and low-fat dairy products resulted in significant decreases in blood
pressure in the healthy population (Sacks et al, 2001). However, both Canadian and U.S.
populations appear to consume low amounts of potassium which fall below the recommended
intake level. The Total Diet Study used CCHS 2.2 food intake data to determine that 68.5-98.8%
of Canadians were consuming less potassium than the AI, across all age groups (Tanase et al,
2011). In the U.S., the average potassium intake of people 2 years and older is 2640 mg/day
according to NHANES 2009-2010 data (Hoy & Goldman, 2012).
Although no clinical trials have examined the effects of a dietary potassium restriction on
preventing hyperkalemia, studies have demonstrated that an oral potassium load (0.25 mmol/kg
body weight) can produce a significant increase in serum potassium in patients with end-stage
renal disease (Allon et al, 1993; Fernandez et al, 1986). Thus, it is presumed that excessive
dietary potassium intake in CKD can lead to hyperkalemia which is associated with fatal
arrhythmias. In one study by Noori et al (2010), higher dietary potassium intake, as estimated by
a food frequency questionnaire, was associated with increased mortality in patients on
hemodialysis.
2.2.3.1.1 Food sources of potassium
A food containing a high amount of potassium is commonly considered to have >200 mg
potassium per serving. The highest sources of dietary potassium include fruits, vegetables,
legumes and dairy products (Sanghavi et al, 2013). However, even a low potassium food can
significantly contribute to daily potassium intake if consumed in large quantities. Therefore,
guidelines for potassium intake often specify a maximum daily serving size for low to moderate
potassium containing foods (ORN, 2013).
According to NHANES data from 2009-2010, fruits and vegetables contributed 20% of
dietary potassium intake in the US, while meats and poultry contributed 10% of total intake (Hoy
& Goldman, 2012). According to Canadian Community Health Survey (CCHS) 2.2 data, the
contribution of potassium from MPF increased with age. Men and women between the ages of
19-70 consumed 14.1% and 12% of their potassium intake from MPF, respectively (Tanase et al
2011). The major source of dietary potassium in Canada came from milk and dairy products
(Tanase et al, 2011).
15
Commercially available salt substitutes are often in the form of potassium chloride and
contain very high amounts of potassium. For instance, the salt-substitute brand Nu-Salt®
contains 3144 mg per teaspoon (www.nusalt.com), which is more than the recommended daily
intake for a patient requiring a potassium restriction. The salty flavor of potassium chloride and
its high potassium content has raised questions about the potential therapeutic role of salt
substitutes in exerting a blood pressure lowering effect. The China Salt Substitute Study (2007)
was a randomized controlled trial that compared the effects of a salt substitute (65% sodium
chloride, 25% potassium chloride, 10% magnesium sulphate) versus sodium chloride on a rural
Chinese population. Results demonstrated that after one-year, participants receiving a salt
substitute had significantly lower blood pressure and the salt substitute was generally well
accepted by participants (Li et al, 2009).
However, there have been several case-reports of life-threatening hyperkalemia due to
salt substitute use in patients with CKD, as well as patients with impaired renal potassium
handling (Ray et al, 1999; Doorenbos & Vermeij, 2003; John et al, 2011). Medical conditions
associated with impaired renal potassium handling include diabetes, severe heart failure, adrenal
insufficiency and kidney disease (IOM, 2005). In addition, medications such as potassium-
sparing diuretics, angiotensin converting enzyme inhibitors and angiotensin receptor blockers
can significantly impair urinary potassium excretion (IOM, 2005). Due to the increased
prevalence of conditions causing impaired potassium excretion and widespread use of
potassium-sparing medications, the number of people at risk for hyperkalemia is likely to
increase (Doorenbos & Vermeij, 2003). It is therefore imperative that patients are educated about
the potential adverse effect of salt substitutes due to its high potassium content.
2.2.3.1.2 Potassium additives in foods
There are many potassium additives that are used in various food products, such as
potassium chloride, potassium lactate, potassium phosphates, potassium sorbate, and potassium
citrate, among others. Potassium chloride is the most frequently used substitute for sodium
chloride, due to its salty taste and functional effects. Potassium lactate and potassium phosphate
are often used to improve shelf-life, retain moisture and improve texture in meat and poultry
products (Desmond, 2006).
16
To our knowledge, there is no Canadian study that has reported the amount of potassium
in food products which contain potassium additives. Sherman and Mehta (2009b) chemically
analyzed the potassium content of 36 uncooked meat and poultry products in the United States
and found large variability between products. The authors noted the top five enhanced products
with the most potassium contained 692-930 mg potassium per 100 grams, which is significantly
greater than the average potassium content of meat and poultry products of the same weight
(~300-375 mg/100g).
Approximately 85% of dietary potassium is absorbed in the healthy individual (Holbrook
et al, 1984), however bioavailability is much higher with potassium salts. Braschi et al (2009),
substituted 30% of sodium in bread with potassium salts and determined that the incorporated
potassium chloride was entirely bioavailable.
2.2.3.2 Potassium labelling regulations in Canada
Information regarding the potassium content of foods is generally not available for
consumers on the Nutrition Facts table (NFt). Health Canada specifies that it is only mandatory
for food manufacturers to list the potassium content on the NFt, if there is a specific product
claim such as “a source of potassium” or “sodium-reduced” with the use of potassium salts
(CFIA, 2014, CFIA 2015b). The food item needs to contain 350 mg of potassium or more in
order to be considered a source of potassium and the amount of potassium must be listed on the
NFt if this claim is used. The daily value listed on the NFt is based on an intake of 3500 mg
potassium per day, however Health Canada has proposed to increase this amount to 4700 mg per
day (Health Canada, 2015a).
Health Canada allows for a disease risk reduction claim with respect to sodium and
potassium that manufacturers can display on their product label. An example of a disease risk
reduction claim is “a healthy diet containing foods high in potassium and low in sodium may
reduce the risk of high blood pressure, a risk factor for stroke and heart disease. (Naming the
food) is a good source of potassium and low in sodium”. Manufacturers may perceive the
addition of potassium to foods to be advantageous for the general population. This perceived
advantage may in turn lead to further additions of potassium to the food supply in the form of
additives, and poses concern for those with CKD.
17
Health Canada (2012b) permits the use of potassium lactate in cooked and uncooked
meat and poultry products as it is an antimicrobial agent that prevents spoilage. Potassium lactate
was approved for use for injection and/or a cover solution for the curing of meat and poultry
products in amounts that were equivalent to 2-4% of the product’s weight (Health Canada,
2012b). At its maximum use (4%) this would contribute 1200 mg of potassium to a 100 g meat
or poultry product. Health Canada’s safety assessment of potassium lactate determined that “the
additional dietary intake of potassium per person on a daily basis would be up to 2471 mg
potassium per day” (Personal communication with Mr. P Loeven, Health Canada Aug 7, 2013).
This is a concerning amount of potassium, especially for those patients with CKD requiring a
potassium restriction of 2000 mg of potassium per day.
When potassium chloride is used as a sodium replacer, it is considered a food ingredient
(seasoning) as it provides flavor enhancement, rather than a technological purpose. As of
September 2013, potassium chloride was no longer considered a food additive; therefore
regulations surrounding its use are less specific. Under the FDR there is no established maximum
use in foods, including meat, poultry and fish products (Personal communication with Ms
Lindsay Lukeman, Health Canada 6 May 2015). However, there are certain foods (i.e. white
bread) where salt replacers, such as potassium chloride, are not permitted.
It is important to note that Health Canada recently proposed that potassium be included in
future NFt on all packaged products (Health Canada, 2015b). If the proposed changes are
approved, it would provide important information to help guide those who need to limit dietary
potassium.
2.2.3.3 Potassium labelling regulations in United States
In the U.S., it is not mandatory for food manufacturers to display the potassium content
on the package label of food items. Potassium content declaration is only mandatory if a
potassium-related claim is made on the food (FDA, 2014c). The percent daily value established
for potassium is 3500 mg per day, which is significantly less than the AI (FDA, 2013). A study
based in the United States analyzed over 6000 food products and determined that potassium
content was displayed on the label of less than 10% of food products (Curtis et al, 2013). In
2014, it was proposed that in the future, potassium content be included on the Nutrition Facts
label (FDA, 2014c)
18
Potassium chloride has GRAS status in the U.S. and has been approved by FSIS (2012)
as a tenderizing agent in raw poultry and meat cuts in amounts up to 3%. The FDA has approved
its use in fish and seafood products with no limitation other than good manufacturing practice
(FDA, 2014b).
Potassium lactate has GRAS status in the U.S. and has been approved by FSIS to be used
to inhibit microbial growth on various meat and poultry products. Its use is approved up to 2%
for flavouring and up to 4.8% as an antimicrobial agent in meat and poultry products (FSIS,
2012). Potassium lactate is required to be included on the ingredients list as its common or usual
name (FSIS, 2015). In fish and seafood products, potassium lactate is approved as an ingredient
used in food with no limit other than good manufacturing process (FDA, 2012a). Therefore,
regulations in Canada and in the U.S. differ slightly, as the U.S. allows more potassium lactate in
foods and does not specify the maximum use of additives in fish and seafood products. While
potassium chloride is allowed in poultry products up to 3% in the U.S., there are no limitations
for its use in MPF in Canada.
2.2.4 High sodium intake and its complications in chronic kidney disease
Increased sodium intake in patients with CKD can more readily lead to volume retention
and increased blood pressure (Koomans et al, 1985). Hypertension is highly prevalent in CKD
and is estimated to be present in approximately 80-85% of patients (Whaley-Connell et al, 2008).
Hypertension is an important risk factor for cardiovascular disease, which is the leading cause of
death in patients with CKD (Sarnak & Levey, 2000). Furthermore, sodium restriction in dialysis
patients has been shown to improve control of hypertension, reduce hypotension during dialysis
treatment, and lessen the prescription of anti-hypertensive medication (Kayikcioglu et al, 2009;
Wright & Cavanaugh, 2010).
In patients with CKD who are not on dialysis, a high dietary sodium intake has been
associated with increased proteinuria (Verhave et al, 2004) and has also been shown to negate
the anti-proteinuric effects of angiotensin-converting enzyme inhibitor therapy (Heeg et al, 1989;
Slagman, 2011). Since proteinuria contributes to the progression of kidney disease, dietary
sodium restriction has been implicated in delaying the progression of kidney disease (Weir and
Fink, 2005).
19
There has been some recent controversy regarding the effects of a high sodium intake on
outcomes in the general population due to the fact that not all healthy individuals are salt-
sensitive. For example, Mente et al (2014) only observed substantial increases in blood pressure
in those individuals who consumed very high amounts of sodium (>6g Na/day), and also among
persons who had existing hypertension and were over the age of 55. Blood pressure effects were
modest in patients consuming a moderate sodium intake (3-5g Na/day) and not evident with
those consuming less than 3 grams sodium per day. However, in more advanced renal failure,
almost all patients are considered to have salt-sensitive blood pressure (Ritz et al, 2009).
Therefore, dietary sodium intake is an important consideration in the management on chronic
kidney disease.
2.2.4.1 Dietary sodium restriction
The 2012 KDIGO guidelines state that the benefits of restricting dietary sodium in the
pre-dialysis population “cannot be overemphasized” and recommend a sodium restriction of
<2000 mg per day, unless contraindicated. Similarly, K/DOQI clinical practice guidelines (2006)
recommend a sodium restriction of 2000 mg (85 mmol) per day in patients on hemodialysis in
order to optimize volume status and blood pressure.
These sodium intake recommendations are between the Adequate Intake (AI) of 1500
mg/day and Upper Limit (UL) of 2300 mg/day that was set for the general population (IOM,
2005). According to the 2004 Canadian Community Health Survey (CCHS 2.2), more than 90%
of adult Canadian men and 66% of adult Canadian women consume sodium amounts above the
UL of sodium per day (Barr, 2010). Similarly, approximately 90% of adults in the US consume
in excess of the recommendations (Cogswell et al, 2012).
2.2.4.1.1 Food sources of sodium
Approximately 75% of salt intake is derived from processed foods, whereas the natural
sodium content of food only contributes 10% of total intake (Mattes & Donnelly, 1991).
Moubarac et al (2014), looked at Canadian food expenditure in relation to its caloric content
from 1938 to 2011, and demonstrated that the consumption of ready-to-eat processed foods
increased from 29% to 62%. In Canada, CCHS 2.2 data revealed that the top sources of dietary
sodium were bread, processed meats and pasta dishes, which contributed 14%, 9% 6%,
respectively. The authors concluded that breads were the main source of dietary sodium due to
20
high consumption, whereas processed meats were consumed in lower quantities but were more
nutritionally dense in sodium (Fischer et al, 2009).
Much of sodium diet education for CKD patients focuses on limiting intake of canned,
pickled, and convenience items, as well as cured meat and fish products (ORN, 2013). In order to
achieve this target, renal dietitians suggest eating fresh, unprocessed versions of foods as these
are naturally lower in salt. Patients are also advised to read food labels and search for alternative
products with a lower content of sodium (Venegoor 2009).
2.3 Sodium reduction in Canada
The mean sodium intake of Canadians is about 3400mg per day, which is significantly
higher than the UL of 2300 mg sodium/day (Health Canada, 2010). There is substantial evidence
that associates a high dietary sodium intake with elevated blood pressure (MacGregor et al,
1989; Sacks et al, 2001; Kearney et al, 2005). Elevated blood pressure or hypertension, is
prevalent among Canadians and is considered a major modifiable risk factor for stroke,
cardiovascular disease (CVD) and renal disease (Barr, 2010). CVD is the second leading cause
of death in Canada (Statistics Canada, 2011) and it has been suggested by Penz et al. (2008) that
reducing dietary sodium intake can substantially reduce CVD events. Moreover, high dietary
sodium intake has been shown to be a risk factor for osteoporosis, stomach cancer and asthma
(DeWardener & MacGregor, 2002). It has been estimated that a decrease in average sodium
intake of 1,800 mg per day would result in Canadian health care savings of approximately 1.4 to
3 billion dollars per year (Penz et al, 2008).
2.3.1 Sodium Working Group
As a result of the high intake of sodium by Canadians and its association with disease,
Health Canada established a multi-stakeholder Sodium Working Group in 2007 to develop and
oversee strategies that would result in lowering the sodium intake of Canadians. The strategy
aimed to decrease the mean sodium intake of Canadians to the UL of 2300 mg per day by 2016,
with an ultimate goal to further lower mean dietary sodium intake to the AI of 1500 mg with the
majority of people below the UL (Health Canada, 2010).
In order to achieve this goal, four areas of recommendation were made: 1) improving
education and awareness about the sodium reduction strategy, 2) research pertaining to sodium
21
and sodium reduction, 3) a sodium monitoring and evaluation plan and 4) the voluntary
reduction of sodium in processed foods by various food manufacturers (Health Canada, 2010).
In order to decrease sodium content in the food supply, Health Canada collaborated with
the food industry to establish voluntary sodium reduction targets for each food category. When
establishing targets, there was careful consideration of the current sodium levels in food
categories, food safety, food quality, and feasibility of the targets. Although the Sodium Working
Group was disbanded in the 2011, Health Canada (2012a) published a document which provided
guidance to the food industry to reduce the levels of sodium in processed foods. The sodium
reduction benchmarks included three phased sodium reduction levels for the food industry to aim
to achieve by the end of 2016.
A qualitative survey was conducted with 55 Canadian food companies by Agriculture and
Agri-Food Canada (AAFC, 2013) which provided an update on sodium reduction efforts by the
food industry. Results indicated that most companies surveyed had a sodium reduction strategy
in place and had taken steps to reduce the level of sodium in their products. In addition, the Food
& Consumer Products of Canada determined that the introduction of reduced sodium products
rose 68% (FCPC, 2011). Health Canada is currently collecting dietary intake data through the
Canadian Community Health Survey. The results of this survey will be published in 2016 and
will further help track the progress in reducing dietary sodium intake.
2.3.2 Strategies to reduce sodium in meat, poultry and fish products
There are many key functional properties of salt and sodium-containing additives that
need to be taken into consideration when reducing sodium levels of foods. Salt, also known as
sodium chloride, is comprised of 40% sodium by weight and is the major contributor of sodium
in the diet (AAFC, 2013). In addition to being used for flavouring, salt and sodium act to help
with preservation, fermentation, microbial safety, leavening, protein binding, and the
development of texture and colour (AAFC, 2013).
Processed meat, poultry and fish products are significant sources of sodium in the diet.
In Canada, 19% of dietary sodium comes from processed meat, red-meat based dishes, poultry-
meat based dishes and fish and shellfish (Fischer et al, 2009). Salt has been used for centuries to
preserve MPF products as salt decreases water-activity, thus extending the shelf-life of the
22
product (Doyle & Glass, 2010). In meat products specifically, salt increases the water-binding
capacity by increasing binding properties of proteins to improve texture (Desmond, 2006). It
solubilizes muscle protein which allows gel formation and optimum texture in processed meat
products that are emulsified (i.e. frankfurters, bologna). Thus, reducing the amount of salt can
have major implications in the flavor, texture and shelf-stability of MPF products. A recent study
by Miller et al (2015) demonstrated that sodium-reduced ready-to-eat meat products in Canada
contained higher bacterial diversity than regular counterparts.
Some of the strategies food manufacturers may use to reduce the sodium content of their
products include reducing sodium content gradually, replacing salt with other chloride salts or
using non-chloride based salts (Verma & Banerjee, 2012). A salt reduction of 10-25% might be
accomplished without having unfavorable effects on palatability of the product (CTAC, 2009). In
addition, it is beneficial for the reduction of salt to happen slowly so that it does not affect
consumer acceptability of the product (Desmond, 2006). Over time, it has been shown that
consumers are able to become more sensitive to a salty taste and adapt to lower sodium levels
(Bertino et al, 1982). The most frequently used chloride-based salt substitute is potassium
chloride, although magnesium chloride and calcium chloride have also been used. The most
common non-chloride based salt substitute is phosphate-based additives (Verma and Banerjee,
2012).
2.3.2.1 Use of potassium additives in sodium reduction of foods
Potassium chloride provides a salty flavour which allows for products to have a similar
perceived saltiness as salt, but that can be achieved with a lower sodium content (Desmond,
2006). It has been estimated that potassium chloride can replace up to about 30% of sodium
chloride in many foods (Doyle & Glass, 2010). The use of potassium chloride is limited as it
produces a bitter and metallic after taste, therefore it is often mixed with sodium chloride to form
a blend (Verma & Banerjee, 2012). Bitter blockers or taste enhancers, such as tricalcium
phosphate, can be used to mask the unpleasant flavours produced by potassium chloride (CTAC,
2009).
As mentioned previously, the DASH diet indicated that a diet lower in sodium and higher
in potassium has a blood pressure lowering effect (Sacks et al, 2001). Therefore, the addition of
potassium salts to foods can be perceived as being advantageous to food manufacturers and the
23
general population. While the U.S. Dietary Guidelines (2005) mentioned that salt substitutes can
be harmful for individuals with certain medical conditions, the guidelines also stated that a diet
rich in potassium blunts the effect of salt on blood pressure and increased dietary intake of
potassium may especially benefit certain populations who have a high prevalence of
hypertension. Health Canada’s sodium reduction strategy (2010) suggested that it would be
beneficial for food manufacturers to first reduce the use of salt, and use salt substitutes when it is
necessary.
Since sodium plays a key role in preservation and microbial safety, when it is removed
from meat products it can pose a food safety concern and reduce the shelf-life of the product.
Lactates, such as potassium lactate, are effective in controlling microbial growth in meat and
poultry products (Health Canada, 2012b) and can enhance saltiness (Dotsch et al, 2009). This
effect is further enhanced with the combination of potassium lactate and sodium diacetate which
act synergistically and can reduce sodium chloride levels by 40% in packaged cooked meats
(Doyle & Glass, 2010). Additionally, Gou et al. (1995) demonstrated that 40% of sodium
chloride could be substituted using a potassium chloride and potassium lactate mix, in dry cured
pork loins. Potassium lactate is therefore an effective sodium replacement that can extend the
shelf-life of meat and poultry products.
2.3.2.2 Use of phosphorus additives in sodium reduction of foods
Several studies have shown that phosphates, such as sodium polyphosphate, are useful to
help lower the sodium content of meat products as they increase the water holding capacity and
improve cooking yield (Verma & Banerjee, 2012). Phosphorus additives and salt act
synergistically, which reduces the requirement of salt from 3-3.5% to 1.4-1.8% (Shults et al,
1972). Phosphorus additives are most commonly found in cured pork products (ham, bacon),
pulverized meats (frankfurters, bologna), precooked breakfast sausages, deli meats, breaded
chicken products, and poultry that has been enhanced or seasoned (Lampila, 2013). Sodium
phosphate is the second highest source of sodium in meats, after sodium chloride, and contains
approximately 30% sodium (Ruusunen et al, 2002).
In meat products, solutions containing sodium phosphates, potassium salts (U.S. only),
and/or spices can be injected into the fresh meat or poultry products. These products are as
labelled “seasoned” in Canada or “enhanced” in the United States (CFIA, 2013; FSIS 2014).
24
Meat and poultry are often seasoned to help maintain tissue integrity which results in a more
moist and tender product, even when cooked (Murphy-Gutekunst & Uribarri 2003). In addition,
the injection of sodium phosphates reduces purge, which is the liquid that is released from raw
meat as it ages, and can be perceived as being undesirable by consumers (Murphy-Gutekunst &
Uribarri, 2005).
In fish and seafood, phosphorus additives help with the retention of moisture and flavor,
the prevention of lipid oxidation, protection from freezer damage, prevention of struvite in
canned seafood and preservation (Lampila, 1992). Sodium tripolyphosphate is also used as a
processing aid to mechanically peel shrimp from its shell, by dipping shrimp in a 3-5%
phosphate solution for 5 minutes prior to cooking it (Lampila, 2013). Similar to meat and poultry
products, phosphates act synergistically with sodium phosphate allowing for less use of salt in
the final product (Lampila, 1992). Fish and shellfish only contribute 2% of dietary sodium intake
of Canadians (Fischer et al, 2009), therefore the food industry may focus their sodium reduction
efforts on food groups that are higher contributors of sodium intake.
Potassium phosphates, such as potassium tripolyphosphate and tetrapotassium
pyrophosphate, are helpful for further reductions of sodium in meat products. They provide the
many favourable effects of phosphate additives and also provide a salty flavor due to the
potassium. In addition, they are effective in terms of water binding and gelation (Verma &
Banerjee, 2012). The extent of sodium reduction depends on the type of potassium phosphates
used and their sodium content (Ruusunen, 2002). In 2014, tripotassium phosphate, potassium
tripolyphosphate and sodium potassium hexametaphosphate were approved for use in Canada as
sodium analogues in the sodium reduction of foods (Health Canada, 2014). Some of the
conditions in which they were approved for use include reducing processing losses in fish and
seafood products, acting as a curing agent in meat and poultry products, and reducing fluid losses
during the thawing of fish.
25
3.0 Rationale and Objectives
Approximately three million Canadians either have chronic kidney disease (CKD), or are
at risk of developing CKD (Arora et al, 2013). As kidney function decreases, the body is unable
to excrete sufficient amounts of phosphorus and potassium through the urine, which can lead to
hyperphosphatemia and hyperkalemia (Kopple & Massry 2004).
Hyperphosphatemia is associated with an increased risk of death in patients in later stages
of CKD and those receiving dialysis (Block et al, 1998; Kestenbaum et al, 2005; Palmer et al,
2011). Guidelines recommend patients with hyperphosphatemia restrict their dietary intake of
phosphorus to between 800 and 1000 mg per day (K/DOQI, 2003). Phosphorus additives can
contribute up to 1000 mg phosphorus per day to the average American diet making adherence to
a low phosphorus diet challenging (Bell et al, 1977; Uribarri & Calvo, 2003).
Hyperkalemia is common in patients with chronic kidney disease and can lead to
increased risk of mortality, due to its effect on cardiac conductivity (Putcha & Allon, 2007).
Potassium chloride is the most frequently used salt substitute due to its salty taste and functional
effects (CTAC, 2009). The use of potassium salts has been associated with toxicity in patients
with CKD (Ray et al, 1999; Doorenbos & Vermeij, 2003; John et al, 2011).
In Canada, it is not mandatory to report phosphorus or potassium content on food labels,
unless there is a related nutrient claim. Therefore, it is difficult to accurately estimate the
potassium and phosphorus content of foods with additives. Studies in the United States and
Europe have shown that the addition of phosphorus and potassium additives significantly
increases the phosphorus and potassium content of the food item (Sherman & Mehta, 2009a;
Benini et al, 2011). To our knowledge, no such studies have taken place in Canada. Accurately
estimating the phosphorus and potassium content of foods is necessary to help CKD patients
choose appropriate foods and adhere with their diet restrictions. This in turn may help prevent
hyperphosphatemia, hyperkalemia and their respective adverse health effects.
In 2007, Health Canada formed the Sodium Working Group to develop, implement and
oversee a strategy to lower the sodium content of Canadians’ diets to within the recommended
range. The strategy included a voluntary reduction of sodium in processed foods by
manufacturers. The food industry suggested methods to reduce sodium content of foods without
26
compromising taste and food safety. Some of these suggestions include the addition of potassium
salts and phosphate-containing additives, especially in processed meats (CTAC, 2009). This
creates a concern among people suffering with ESRD, in which a diet high in protein (1.2
g/kg/day) and low in sodium (less than 85 mmol or 2000 mg per day) is recommended (KDOQI,
2000; KDIGO, 2012). Patients with ESRD are educated to increase their intake of protein from
sources such as meat, poultry and fish, as well as choose lower sodium food products, which
may unintentionally lead to an increased intake of phosphorus and potassium (Venegoor, 2009).
The overall aims of our study was to gain knowledge of the actual content of total
phosphorus and potassium content in commonly consumed meat, poultry and fish products,
among the CKD population, and to determine if the sodium reduction of processed foods is
associated with increased amounts of phosphorus and potassium additives.
We hypothesized that MPF foods containing phosphorus and potassium additives will
contain higher amounts of phosphorus and potassium compared to foods without these additives.
In addition, we hypothesized that sodium reduced foods will contain higher amounts of
phosphorus and potassium compared to its original non-sodium reduced counterpart. In order to
test our hypotheses we conducted three studies:
Study 1: Commonly consumed meat, poultry and fish (MPF) products among patients with
End-Stage Renal Disease at a Tertiary Care Teaching Hospital in Toronto, Canada: Food
Questionnaire. The primary objective of this study was to identify the most commonly
consumed MPF products among patients receiving dialysis. Our secondary objective was to
describe the patient’s purchasing and food preparation behaviours related to MPF products. The
results helped to guide the selection of foods for study 2 (food analysis).
Study 2: Phosphorus and potassium content of commonly consumed meat, poultry and fish
products among patients with CKD. The aim of this study was to gain knowledge of the actual
content of added phosphorus and potassium of commonly consumed meat, poultry and fish
products, among the CKD population. Specific objectives were:
1) To determine whether and to what extent the chemically analyzed phosphorus,
potassium, sodium and protein contents differ among commonly consumed MPF
products with and without additives listed on their ingredient list.
27
2) To determine whether and to what extent the chemically analyzed phosphorus,
potassium, sodium and protein contents differ among poultry products with and without
the term ‘seasoned’ on the product label.
Study 3: Do Sodium Reduced Meat and Poultry Products Contain a Significant Amount of
Potassium and Phosphorus from Additives? The objective of this study was to determine
whether and to what extent the reduction of sodium in meat and poultry products is associated
with higher amounts of potassium and phosphorus from food additives.
28
4.0 Commonly consumed meat, poultry and fish products among patients with
End-Stage Renal Disease at a Tertiary Care Teaching Hospital in Toronto,
Canada: Food Questionnaire
4.1 Introduction
Hyperphosphatemia is a common condition in chronic kidney disease (CKD) and is
associated with an increased risk of mortality (Block et al, 1998; Kestenbaum et al, 2005;
Palmer, et al 2011). Hence, the prevention and correction of hyperphosphatemia is a key aspect
in the management of CKD. Methods to lower serum phosphorus levels include the use of
phosphate binding medication, dialysis therapy and restriction of dietary phosphorus intake.
Approximately 20-30% of the dietary phosphate intake comes from animal protein such as, meat,
fish, poultry, milk and eggs (Calvo & Park, 1996), however, patients requiring dialysis are
advised to increase their intake of these high biological value protein sources.
There is concern that additives containing phosphorus are increasingly being used to
enhance the properties of meat, poultry and fish (MPF) products (Uribarri & Calvo, 2003).
Several studies have compared the nutrient content of MPF products that contained additives
with additive-free products. These studies showed the phosphorus content increased by
approximately 30-60% in foods containing phosphorus additives. However, the selection of
foods analyzed in these studies was often done arbitrarily (Sherman & Mehta, 2009ab; Sullivan
et al, 2007; Benini et al, 2011).
Current practice is to recommend fresh MPF products, as these are lower in sodium than
processed MPF (Vennegoor, 2009). However, there is no literature to our knowledge that
outlines the main sources of MPF that patients with CKD are purchasing and consuming. Studies
that did investigate the dietary intake of patients with ESRD did not report on the details, such as
specific types of MPF foods that were purchased (Fassett et al, 2007, Khoueiry et al, 2011;
Kalantar-Zadeh et al, 2002). Furthermore, studies describing types of foods consumed in the
general population may not be generalizable to the hemodialysis population due to the numerous
dietary restrictions that alter food intake patterns from those of healthy individuals (Kalantar-
Zadeh et al, 2002).
29
The primary objective of this study was to identify the most commonly consumed MPF
products among patients receiving dialysis. Our secondary objective was to describe the patient’s
purchasing and food preparation behaviours related to MPF products.
The results of this project will provide guidance for the evidence-based selection of foods
for the next phase of our study, in which we will analyze and compare the nutrient content of
MPF products with and without food additives. The results will ensure the MPF items chosen are
relevant to the dialysis patient population in a tertiary care teaching hospital in Toronto, Canada.
4.2 Materials and Methods
4.2.1 Design
This was a cross-sectional survey that involved hemodialysis and peritoneal dialysis
patients at St. Michael’s Hospital in Toronto, Canada. The food frequency questionnaire was
developed specifically for the purposes of this study and underwent a face validation process
with patients and health care practitioners. Ethics approval was obtained from the Research
Ethics Boards at both St. Michael’s Hospital and the University of Toronto. Informed written
consent was obtained from each participant.
4.2.2 Patient questionnaire development
Questions pertaining to the consumption of MPF products were extracted from the
Canadian Diet History Questionnaire II (DHQ II), adapted from the National Institute of Health
DHQ II(Csizmadi et al, 2007). The DHQ is a validated food frequency questionnaire with a
correlation coefficient of 0.48 between energy intake from DHQ and estimated truth by four 24-
hour recalls (Subar et al, 2001). Meat products included beef and pork based products. Poultry
products included chicken and turkey based products. Fish products included white fish,
dark/pink fish, and shellfish products. Food frequency questions pertaining to both processed and
unprocessed MPF were included as part of the patient questionnaire. The self-reported adherence
to renal restriction questions were extracted from the Block Dialysis I Food Frequency
Questionnaire (Kalantar-Zadeh et al, 2011). The questionnaire was designed to be a self-
administered, however, assistance from a research assistant was provided as needed.
The questionnaire consists of 40 questions within four principal domains (Appendix A);
30
1) Frequency, types, and brands of MPF products consumed (23 questions).
2) Purchasing and preparation behaviours (10 questions)
3) Self-reported adherence to renal restrictions (2 questions)
4) Demographic and clinical data (5 questions)
4.2.3 Face validation of patient questionnaire
The questionnaire was tested for face validity among a group of nephrology health care
professionals (n=6) and ESRD patients (n=6). Health care professionals who provided verbal
consent to participate in the face validation process were sent an e-mail by the principal
investigator outlining the study and face validation process. They were asked to provide
feedback on the readability, content, and appropriateness of questions.
In addition, patients receiving hemodialysis or peritoneal dialysis at St. Michael’s
hospital were approached by a research assistant using a recruitment pre-amble for face
validation (Appendix B). Following their consent, patients were asked to review the
questionnaire and provide comments directly on the questionnaire with specific regards to the
readability, clarity and appropriateness of the questions.
The questionnaire was revised based on the comments obtained from the face validation
exercise to ensure that questions were appropriate, as well as clear and easy to understand.
4.2.4 Eligibility criteria
Patients with ESRD receiving hemodialysis or peritoneal dialysis at St. Michael’s
Hospital who were able to verbally communicate in English or who had a primary household
shopper who was able to verbally communicate in English were eligible for inclusion into the
study.
Patients were ineligible if they and/or their primary caregiver did not cook at home and/or
were unable to grocery shop (i.e. if they lived in a nursing home or received meals on wheels),
were unable to ingest regular solid food, were vegetarian, were receiving palliative care, or had a
major psychiatric disorder or severe dementia.
31
4.2.5 Recruitment methods
All patients receiving in-centre hemodialysis or peritoneal dialysis at St. Michael’s
Hospital were identified and screened for eligibility using the patient census. Eligible
hemodialysis patients were initially approached by their nurse practitioner, while eligible
peritoneal dialysis patients were approached by the dietitian in the peritoneal dialysis clinic. A
scripted pre-amble was used to introduce the study (Appendix C). If the patient expressed
interest in enrolling in the study, they were then approached by a research assistant who was not
within the patient’s circle of care to obtain informed consent (Appendix D).
4.2.6 Questionnaire administration and data collection
The questionnaire was administered to participants by a research assistant during a
routine clinic or dialysis visit. The participant had the choice to complete the questionnaire at the
time of administration, or take it home and return it at their next hospital visit. The research
assistant reviewed completed questionnaires, and clarified any unclear answers with the
participant. Participants were encouraged to answer all the questions but were made aware that it
was not mandatory.
Questions were designed to be self-explanatory. However, participants were encouraged
to ask research assistants for clarification of any questions, or assistance in completing the
questionnaire. The questionnaire took approximately 30 to 45 minutes to complete.
Additional data was collected from the participant’s chart by a trained research individual
using a data collection form (Appendix E). This data included age, sex, dialysis vintage,
significant co-morbidities (diabetes, hypertension and heart failure), anthropometric data (dry
weight or body weight measured post-dialysis, height, BMI) and the most recent biochemical
data (pre-dialysis urea, albumin, phosphorus, calcium, potassium, and percentage reduction in
urea).
4.2.7 Data analysis
This was a sample of convenience as we aimed to screen all patients attending dialysis
during the study recruitment period for eligibility and inclusion in the study (sample pool size of
226). Continuous variables were summarized using means, medians, standard deviations and,
32
minimums and maximums, whereas categorical variables were described using frequencies and
percentages.
Consumption of MPF products was expressed as grams per month. The portion sizes
listed in the questionnaire (from Canadian DHQ II) correspond to gram weights that were sex-
specific, based on actual consumption of foods reported from dietary intake recall data from
Statistics Canada’s Community Health Survey (CCHS 2.2). Consumption per month was
estimated by calculating the product of frequency of consumption (times per month) and portion
size usually eaten (grams). The MPF products were ranked from highest to lowest according to
the estimated mean weight consumption per month. The highest mean weight consumed per
month reflected the most commonly consumed type of MPF.
In addition, servings were defined using the standard food serving sizes from Health
Canada’s Nutrient Value of Some Common Foods (2008). Weight consumption per month was
divided by the standard food serving size in order to determine serving consumption per month
for each type of MPF.
Results 4.4
4.4.1 Participant recruitment
Over the period of July to September 2013, 196 hemodialysis and 30 peritoneal dialysis
patients attended SMH in-centre hemodialysis unit and peritoneal dialysis clinic and were
screened for inclusion in the study. Of the patients screened, 122 hemodialysis and 26 peritoneal
dialysis patients met eligibility criteria. The main reasons for exclusion from the study were: did
not cook at home (49%) and language barrier (31%). Sixty-seven participants provided consent
and completed the questionnaire (Figure 4.1).
4.4.2 Demographic and clinical characteristics of participants
Characteristics of participants are summarized in Table 4.1. Sixty-four percent of
participants were male and the majority (76%) received conventional hemodialysis. The mean
(standard deviation) BMI was 26 (5) kg/m2 and laboratory values were within acceptable ranges
for patients receiving dialysis. The majority of patients (57%) had received post-secondary
education.
33
4.4.3 Commonly consumed meat, fish and poultry products
Ranked sources of MPF products based on weight (g) consumption per month are
summarized in Table 4.2. The top five most commonly consumed types of MPF (based on
estimated product weight) among ESRD patients at St. Michael’s Hospital were unbreaded
chicken, ground beef, steak, white fish and beef burgers.
Participants generally chose fresh options versus packaged types of each MPF. There
were very few participants who commented on brands of MPF purchased, however, those who
did, mentioned popular national brands most often (i.e. Maple Leaf®, Schneider’s
®, and Clover
Leaf®).
Ranked sources of MPF based on number of servings consumed per month by patients
are summarized in Table 4.3. The most commonly consumed types of MPF (based on number of
servings) were unbreaded chicken, ground beef, shrimp, steak and bacon.
4.4.4 Purchasing and preparation behaviours
Purchasing and preparation behaviours are described in the Table 4.4. The most common
grocery stores that participants shopped at were No Frills (60%), Metro (52%) and Loblaws
(39%). Either the participant or their spouse completed the grocery shopping and cooking at
home most often. Fifty-six percent of participants ate a meal outside of their home at least one
time per week. Participants reported checking the sodium, potassium and fat content of foods
most often when examining the Nutrition Facts table (78%, 54% and 51%, respectively). Forty
percent of participants looked for phosphorus in the ingredients list, while 48% looked for
potassium. Eighty-five percent of patients reported never using a salt substitute. Forty-five
percent of participants reported choosing a sodium-free or reduced sodium product most of the
time.
4.4.5 Self-reported adherence to renal diet restrictions
Self-reported adherence to renal restrictions is described in Table 4.4. The majority of
participants answered that they try to adhere to low phosphorus diet (79%), however, 42%
admitted that they don’t always follow it. Similarly, 81% of patients reported trying to follow a
low potassium diet, but 24% admit they don’t always adhere to their diet.
34
Figure 4.1 Flow diagram of subject recruitment and study completion
196 screened in-centre hemodialysis
patients at St. Michaels Hospital
(July-Sept 2013)
74 Ineligibile patients
38 Did not cook at home
24 Language barrier
4 Unable to ingest solid foods
2 Major psychiatric disorder
1 Vegetarian
1 Severe dementia
4 Transferred programs
70 Declined
122 met eligibility criteria
52 Enrolled
30 screened peritoneal dialysis patients
at St. Michaels Hospital
(July-Sept 2013)
4 Ineligibile patients
2 Major psychiatric disorder
1 Vegetarian
1 Language Barrier
26 met eligibility criteria
15 Enrolled 11 Declined
67 Enrolled
67 completed the questionnaire
35
Table 4.1 Demographic and clinical characteristics of participants (n=67)
Characteristics Results
Mean (SD) n (%)
Age, years 59 (15)
Sex
Male
Female
43 (64)
24 (36)
Dialysis Vintage†, years 4 (5)
Mode of Dialysis
Conventional (3x/wk) Hemodialysis
Peritoneal Dialysis
Short Daily Hemodialysis
51 (76)
15 (22)
1 (2)
Co-Morbidities
Diabetes
Hypertension
Cardiovascular Disease
29 (43)
54 (81)
17 (25)
Dry Weight††
, kg 73 (21)
Height, cm 165 (12)
BMI, kg/m2 26 (5)
Albumin, g/L 39 (3)
Phosphorus, mmol/L 1.6 (0.5)
Calcium, mmol/L 2.2 (0.2)
Potassium, mmol/L 4.6 (0.7)
Urea, mmol/L 23 (7)
PRU*, mmol/L 78 (7)
Type of home
House
Apartment
Other
26 (39)
38 (57)
3 (4)
# People in Household
No one else
One other
Two others
Three others
4 or more others
10 (15)
28 (42)
13 (19)
11 (16)
5 (8)
Education
Elementary School
Some high school
High school diploma
Some university/college
University/college degree
Graduate
None
3 (5)
7 (10)
18 (27)
10 (15)
20 (30)
8 (12)
1 (2)
Ethnicity**
Aboriginal
African/Black
8 (12)
8 (12)
36
Caribbean
East Asian
Caucasian / White
Middle Eastern
South Asian
South-East Asian
9 (13)
4 (6)
29 (43)
2 (3)
11 (16)
5 (7)
Annual Income
> $100,000
$80,000 -$100,000
$60,000 - $80,000
$40,000 - $60,000
$20,000 - $40,000
< $20,000
5 (8)
3 (5)
7 (10)
12 (18)
18 (27)
2 (3) *measured in patients receiving hemodialysis only (n=51)
**Indicates a questions where the participant can choose more than one answer (check all that apply) †Dialysis Vintage defined as the length of time on dialysis in years
††Dry weight defined as the established amount of body mass (weight) without extra fluid (water)
37
Table 4.2 Ranked Consumption of meat, poultry and fish products based on estimated
weight (g) consumption per month by ESRD patients (n=67)
Rank Source of
MPF
Consumption,
Total grams /
month
Mean (SD)
Serving
size*
(grams)
Zero
consumption
N (%)
Types of MPF consumed**
N (%)
1 Unbreaded
Chicken 888 (1158) 75 2 (3)
Fresh, packaged
Fresh, butcher
Frozen
Rotisserie
I don’t know
Other
45 (67)
22 (33)
10 (15)
14 (21)
1 (1)
2 (3)
2 Ground
Beef 449 (861) 75 13 (19)
Fresh
Frozen
Other
46 (69)
7 (10)
2 (3)
3 Steak 365 (639) 75 14 (21)
Fresh, packaged
Fresh, butcher
Frozen
I don’t know
28 (42)
32 (48)
1 (1)
1 (1)
4 White Fish 281 (635) 75 27 (40)
Fresh, packaged
Fresh, seafood counter
Frozen
Other
11 (16)
21 (31)
12 (18)
3 (4)
5 Burger 243 (315) 75 18 (27)
Fresh, homemade
Frozen
I don’t know
Other
35 (52)
15 (22)
1 (1)
3 (4)
6 Beef 203 (294) 75 20 (30)
Fresh, packaged
Fresh, butcher
Frozen
23 (34)
29 (43)
1 (1)
7 Cold Cuts 182 (606) 56
(2 slices) 32 (48)
Pre-packaged
Deli Counter
Other
14 (21)
23 (34)
3 (4)
8 Canned
Tuna 169 (282) 75 22 (33) n/a n/a
9 Dark Fish 169 (293) 75 31 (46)
Fresh, packaged
Fresh, deli counter
Frozen
Other
15 (22)
5 (7)
3 (4)
1 (1)
10 Pork 164 (313) 75 28 (42)
Fresh, packaged
Fresh, meat counter
Frozen
23 (34)
17 (25)
2 (3)
11 Shrimp 157 (363) 30
(6 medium) 28 (42)
Fresh, seafood counter
Frozen, unbreaded
Frozen, breaded
Other
14 (21)
29 (43)
2 (3)
3 (4)
12 Poultry
Cold Cuts 147 (235) 56 30 (45)
Pre-packaged
Deli Counter
17 (25)
24 (36)
13 Hot Dog 116 (401) 38 (1) 30 (45) Fresh, packaged
Fresh, deli counter
26 (39)
5 (7)
38
*Serving sizes were determined by Health Canada’s Nutrient Value of Some Common Foods, 2008
**Indicates a questions where the participant can choose more than one answer (check all that apply)
Frozen
I don’t know
Other
3 (4)
1 (1)
4 (6)
14 Breaded
Chicken 116 (280) 75 35 (52)*
Fresh, breaded
Frozen
Other
14 (21)
17 (25)
6 (9)
15 Sausage 115 (486) 75 40 (60)*
Fresh, packaged
Fresh, deli counter
Other
16 (24)
7 (10)
1 (1)
16 Bacon 109 (434) 24
(3 slices) 36 (54)*
Fresh, packaged
Fresh, meat counter
I don’t know
Other
28 (42)
4 (6)
1 (1)
4 (6)
17 Deli Ham 103 (202) 56
(2 slices) 33 (49)
Pre-packaged
Deli Counter
13 (19)
24 (36)
18 Canned
Salmon 82 (275) 75 41 (61)* n/a n/a
19 Breaded
Fish 81 (260) 75 39 (58)*
Fresh, battered
Frozen
7 (10)
21 (31)
20 Ham 68 (448) 75 57 (85)*
Packaged, cooked
Meat Counter
Other
5 (7)
4 (6)
1 (1)
21 Turkey 57 (96) 75 41 (61)*
Fresh, packaged
Fresh, butcher
Frozen
Other
13 (19)
6 (9)
6 (9)
3 (4)
22 Ribs 53 (95) 75 35 (52)*
Fresh, packaged
Fresh, meat counter
Frozen
Other
11 (16)
16(24)
5 (7)
3 (3)
23 Shellfish 31 (840) 75 45 (67)*
Fresh, seafood counter
Frozen
Other
13 (19)
8 (12)
1 (1)
39
Table 4.3 Ranked sources of meat, poultry and fish Products, based on number of servings
consumed per month by ESRD patients
Rank Source of MPF Serving size
(g)
Total number of servings
consumed per month
Mean (SD)
Zero
consumption
N (%)
1 Unbreaded Chicken 75 11.8 (15.4) 2 (3)
2 Ground Beef 75 8.0 (15.4) 13 (19)
3 Shrimp 30 (6 medium) 5.2 (12.1) 28 (42)
4 Steak 75 4.9 (8.5) 14 (21)
5 Bacon 24 (3 slices) 4.6 (18.1) 36 (54)*
6 White Fish 75 3.8 (8.5) 27 (40)
7 Cold Cuts 56 (2 slices) 3.3 (10.8) 32 (48)
8 Burger 75 3.2 (4.2) 18 (27)
9 Hot Dog 38 (1) 3.1 (10.6) 30 (45)
10 Beef 75 2.7 (3.9) 20 (30)
11 Poultry Cold Cuts 56 2.6 (4.2) 30 (45)
12 Canned Tuna 75 2.3 (3.8) 22 (33)
13 Dark Fish 75 2.2 (3.9) 31 (46)
14 Pork 75 2.2 (4.2) 28 (42)
15 Deli Ham 56 (2 slices) 1.8 (3.6) 33 (49)
16 Breaded Chicken 75 1.6 (3.7) 35 (52)*
17 Sausage 75 1.5 (6.5) 40 (60)*
18 Canned Salmon 75 1.1 (3.7) 41 (61)*
19 Breaded Fish 75 1.1 (3.5) 39 (58)*
20 Ham 75 0.9 (6.0) 57 (85)*
21 Turkey 75 0.8 (1.3) 41 (61)*
22 Shellfish 75 0.4 (1.1) 45 (67)*
23 Ribs 75 0.1 (1.3) 35 (52)*
* Greater than 50% (n=34) of patients do not consume source of MPF
40
Table 4.4 Purchasing, food preparation behaviours and self-reported adherence to renal
diet restrictions
Question Results n (%)
Purchasing and Preparation Behaviours
*At which grocery store(s) do
you shop?
Sobey’s 16 (24)
Metro 35 (52)
No Frills 40 (60)
Loblaws 26 (39)
Great Canadian Superstore 8 (12)
Costco 15 (22)
Other 26 (39)
*Who does the grocery shopping
at home?
You 37 (55)
Spouse 28 (42)
Children 9 (13)
Caregiver 3 (5)
Other 2 (3)
*Who does the cooking at
home?
You 40 (60)
Spouse 23 (34)
Children 8 (12)
Caregiver 5 (8)
Other 4 (6)
During the past month, how
often did you eat a meal outside
of the home (includes
restaurants, fast food, coffee
shops)?
More than once a day 4 (6)
Once a day 3 (5)
4-5 times per week 7 (10)
2-4 times per week 16 (24)
1-2 times per week
2-3 times per month
10 (15)
6 (9)
Once per month 12 (18)
Less than once per month 9 (13)
*If you read the Nutrition Facts
table (see picture) to find out
about the nutritional content of
the food, what do you usually
look for?
Calories 21 (31)
Sodium 52 (78)
Fat 34 (51)
Protein 15 (22)
Phosphorus 23 (37)
Potassium 36 (54)
Carbohydrate 10 (15)
Sugar 28 (42)
Fiber 12 (18)
I don’t read the Nutrition Facts Table 6 (9)
I don’t know 2 (3)
Do you use the salt substitute,
called NoSalt©, NuSalt© or
HalfSalt©, when you cook?
I often use a salt substitute 3 (5)
I sometimes use a salt substitute 7 (10)
I never use a salt substitute 57 (85)
I don’t know 0 (0)
*If you read the list of I don’t read the ingredient list 23 (34)
41
ingredients of the food you buy,
what do you usually look for?
Ingredients with the word “phosphorus” or letters
“phos”
27 (40)
Ingredients with the word “potassium” 32 (48)
Other 17 (25)
How often do you try to choose
foods that say “Sodium-Free” or
“No Sodium” or “No Added
Salt” on the food package?
Most of the time 30 (45)
Some of the time 19 (28)
Never 14 (21)
I don’t know 4 (6)
How often do you try to choose
foods that say “Reduced in
Sodium” or “25% Less Sodium”
or “Lightly Salted” or “Lower
in Sodium” on the package?
Most of the time 30 (45)
Some of the time 18 (27)
Never 17 (25)
I don’t know 2 (3)
Self-reported adherence to renal restrictions
If you are asked to follow a low
phosphorus diet, do you think
you are following it?
I am not asked to follow a low phosphorus diet
7 (10)
I try to follow a low phosphorus diet and I usually
do
25 (37)
I try to follow a low phosphorus diet, but I don’t
always follow it
28 (42)
I don’t follow a low phosphorus diet 3 (5)
I don’t know what a low phosphorus diet is 4 (6)
If you are asked to follow a low
potassium diet, do you think you
are following it?
I am not asked to follow a low potassium diet
6 (9)
I try to follow a low potassium diet and I usually do 38 (57)
I try to follow a low potassium diet, but I don’t
always follow it
16 (24)
I don’t follow a low potassium diet 6 (9)
I don’t know what a low potassium diet is 1 (1) * Indicates a question where the participant can choose more than one answer (check all that apply)
42
Table 4.5 Characteristics of study patients receiving hemodialysis as compared with the
Canadian Institute for Health Information data
Study Participants
(2013)
SMH CIHI
(2012)
Province
CIHI (2012)
Canada CIHI
(2012)
n = 52 n = 248 n = 8,160 n = 14, 632
Age, Mean (SD) 59.4 (13.7) 60 (14) 65.2 (15.3) 64.9(15.4)
Male, % 67.3 59.1 58.4 58.7
Caucasian Race, % 42 43 65 64
Diabetes, % 38.5 44.0 48.3 47.4
BMI, Mean, kg/m2 26.1 26.5 28.5 28.6
Phosphorus,
Mean (SD), mmol/L
1.6 (0.5) 1.5 (0.5) 1.6 (0.5) 1.7 (0.5)
Calcium,
Mean (SD), mmol/L
2.2 (0.2) 2.3 (0.2) 2.4 (0.3) 2.3 (0.2)
Albumin,
Mean (SD), g/L
39.5 (3.1) 38.8 (4.2) 36.2 (5.2) 35.6 (5.2)
Table 4.6 Characteristics of study patients receiving peritoneal dialysis as compared with
the Canadian Institute for Health Information data
Study Participants
(2013)
SMH CIHI
(2012)
Province
CIHI (2012)
Canada CIHI
(2012)
n = 15 n = 52 n = 1,538 n = 3,128
Age, Mean (SD) 59.7 (17.7) 66.1 (15.6) 63.6 (15.0) 62.4 (14.9)
Male, % 53.3 61.5 58.2 58.5
Caucasian Race, % 46.7 40.4 60.5 61.2
Diabetes, % 40.0 51.9 44.7 42.1
BMI, Mean, kg/m2 27.6 25.1 27.4 27.6
Phosphorus,
Mean (SD), mmol/L
1.7 (0.6) 1.5 (0.5) 1.6 (0.5) 1.7 (0.5)
Calcium,
Mean (SD), mmol/L
2.2 (0.2) 2.4 (0.2) 2.5 (0.2) 2.4 (0.2)
Albumin,
Mean (SD), g/L
36.7 (3.8) 36.4 (4.5) 34.0 (5.5) 33.6 (5.6)
*Source: Canadian Institute for Health Information. Canadian Organ Replacement Register (2014):
Centre-Specific Clinical Measures Report of Dialysis Patients in Canada 2010 to 2012
Abbreviations: SMH = St. Michael’s Hospital; CIHI = Canadian Institute for Health Information;
BMI = Body Mass Index
43
4.5 Discussion
The results of the dietary survey indicate that unbreaded chicken is the most commonly
consumed source of MPF among patients with ESRD at St. Michael’s Hospital. Ground beef,
steak, white fish and burgers were also among the most common MPF foods consumed by
weight. These results are in line with Agriculture Canada data (2013) which demonstrates
chicken is the most commonly consumed animal protein per capita in Canada. Similarly,
NHANES 2007-2010 data showed that poultry and beef were the top sources of dietary animal
protein (Pasiakos et al, 2015). The majority of participants tended to choose fresh versions of
MPF, which is recommended by their dietitian as part of a renal diet. This study was the first
Canadian study to describe the most frequently consumed types of MPF products among patients
with ESRD.
We also examined MPF consumption based on the number of servings consumed per
month as the typical serving size consumed varies per type of MPF. For example, the standard
serving size of solid cuts of meat and poultry is 75g; however, the standard serving for deli meat
and bacon is only 56g and 24g, respectively. While five out of the top eight foods were identical
to those shown by consumption by weight; shrimp, bacon and cold cuts were considered
commonly consumed MPF based on serving size. Bacon and cold cuts are not a part of a low
sodium diet indicating that patients are often non-adherent to low sodium diet restrictions. A
recent study among CKD patients in England, demonstrated that 87% of patients reported
consumption of canned or processed meats at least once per week (Nerbass et al, 2014).
Participants shopped at No Frills, Loblaws and Metro most often, which are among the
top grocery store chains in Canada (Mintel, 2009; Schermel et al, 2013). Twenty-one percent of
participants eat a meal outside of the home at least 4-5 times per week. Another 24% of
participants eat meals outside the home 2-4 times per week. This is slightly lower than studies
that analyzed the CCHS 2004 data, which reported that 29% of adults in Ontario had eaten at a
fast food outlet on the day before their interview (Garriguet, 2004).
The majority of participants (78%) reported that they actively read the sodium content on
food labels and tried to purchase products that were low in sodium, contained no added salt or
were reduced in sodium. However, Wong et al (2013) demonstrated that Canadian consumers do
44
not seem to differentiate between different types of sodium claims. This is of concern as the
sodium content can vary widely depending on the type of claim that is displayed on the product.
To our knowledge there is no other data that describes the most commonly consumed
types of MPF products in the CKD population. Studies that have looked at dietary intake in the
CKD population have ranked food consumption according to specific nutrient intakes (Khoueiry
G et al. 2011; Fassett RG et al. 2007). Kalantar-Zadeh et al (2011) used a 3-day food record to
rank sources of energy intake among 154 hemodialysis patients in South Bay, Los Angeles, CA.
The most frequently consumed items (n=55) represented 83% of patients’ energy intake. The
study concluded that the top 5 sources of MPF according to percent of energy intake were eggs
or breakfast sandwiches with eggs; beef (fat off); chicken, not fried (no skin); mixed dish with
beef or pork; and hamburgers. The results are difficult to compare to ours as they ranked MPF
intake according to percent of energy intake and include additional information regarding animal
protein sources we did not inquire about, such as eggs and mixed dishes with beef or chicken. In
addition, the difference in the results between the Kalantar-Zadeh study and ours is possibly due
to the difference in populations of the two geographic areas. South Bay consists mainly of
individuals of Hispanic and African American ethnicity, whereas Toronto has a more ethnically
diverse population.
Our study has several limitations. First, we chose a convenience sample at a single centre
in Toronto, Ontario, which limits the generalizability of the results to the entire dialysis CKD
population. In addition, as this was a convenience sample, the possibility of selection bias cannot
be excluded. While we showed that characteristics, such as age and BMI, were similar to the
SMH dialysis population (see Table 4.5 & 4.6), we were not able to compare aspects such as
education level and household income, which may influence food purchasing and consumption
behaviours. Patients who do not cook at home were excluded from the study, and therefore the
results cannot be extrapolated to patients who obtain food elsewhere. Future studies could
address patients who eat food outside of the home (i.e. patients living in a nursing home or who
rely on fast food), as these are often convenience products which are likely to contain additives.
Lastly, although a wide variety of MPF foods were captured using a validated tool, general
limitations of food frequency questionnaires are that they lack the accuracy to assess the
adequacy of dietary intakes, they rely on the patient’s memory which can affect accuracy of the
results and they may not have adequate coverage to include all MPF food items consumed
45
(Brown, 2006; Bross et al, 2010). For instance, eggs were not included and have been shown to
be a significant source of animal protein intake (Pasiakos et al, 2015; Kalantar-Zadeh et al,
2011).
4.5.1 Conclusions
In conclusion, the most commonly consumed MPF by patients with CKD were chicken,
ground beef, steak, white fish, beef burgers, shrimp, deli ham and bacon. Participants generally
chose a fresh version of MPF products in accordance with a low sodium diet. However, they also
consumed certain types of high-sodium processed MPF products frequently, such as bacon and
deli ham. We conclude that participants often look at the nutrition facts table for the amount of
sodium and potassium. However, less than half of participants look for the word ‘phosphorus’ or
‘potassium’ on the ingredient list, which determines if the product contains additives.
This study provided information on amounts of MPF products consumed, as well as
purchasing and cooking behaviours. The results enabled us to select the most relevant MPF
foods for Canadian patients with ESRD, to be chemically analyzed in the next phase of the study.
46
5.0 Phosphorus and potassium content of commonly consumed meat, poultry
and fish products among patients with CKD
5.1 Introduction
Cardiovascular disease is a leading cause of mortality among patients with chronic
kidney disease (CKD) (USRDS, 2003). Hyperphosphatemia is associated with cardiovascular
mortality (Block et al, 1998; Kestenbaum et al, 2005; Palmer et al, 2011), whereas hyperkalemia
can lead to fatal arrhythmias or sudden cardiac death (Sanghavi et al, 2013). Low potassium and
low phosphorus diets are often prescribed to patients with CKD and form an integral part of their
nutritional therapy to manage and prevent hyperkalemia and hyperphosphatemia (Kopple &
Massry, 2004).
Adherence to low phosphorus and potassium diets is becoming increasingly difficult due
to the addition of phosphorus and potassium additives to foods. Phosphorus additives are often
added to meat, poultry and fish (MPF) products to extend shelf life, improve texture, and
preserve moisture (Lampila, 2013). Sodium phosphates can also be injected into solid cuts of
meat and poultry, in which case it may be labelled as ‘enhanced’ (U.S.) or ‘seasoned’ (Canada).
Several studies conducted in Europe and the United States have demonstrated that phosphorus
additives significantly contribute to the phosphorus content of food (Léon JB et al, 2013; Cupisti
A et al, 2012; Benini O et al, 2011; Sherman & Mehta, 2009b; Sullivan et al, 2007). Recently,
Carrigan et al. (2014) compared chemically analyzed foods from a low additive and an additive-
enhanced 4-day menu. The study demonstrated that a processed diet rich in additives increased
phosphorus content by 60%. To our knowledge, there is no published analytical Canadian data of
foods with phosphorus additives. In addition, studies that have looked at the contribution of
potassium additives to the potassium content of foods are limited (Sherman & Mehta, 2009b).
The problem of additives is compounded by the fact that phosphorus and potassium
contents are not listed on the Nutrition Facts table of food packages, unless there is a specific
nutrient-related claim (CFIA, 2015b; FDA 2013). Therefore, this creates uncertainty as to which
foods are appropriate to consume on a renal diet. In addition, it poses a challenge for renal
dietitians who are often advising patients on dialysis to consume animal sources of protein, many
of which may be hidden sources of phosphorus and potassium. The aim of this study was to gain
knowledge of the actual content of phosphorus and potassium in commonly consumed meat,
47
poultry and fish products, among the CKD population. Specific objectives were to determine
whether and to what extent the chemically analyzed phosphorus, potassium, sodium and protein
content differs among commonly consumed MPF products with and without additives listed on
their ingredient list and among poultry products with and without the term ‘seasoned’ on the
product label.
5.2 Materials and Methods
MPF products were chosen for chemical analysis based on the results of a food frequency
questionnaire (FFQ) administered to hemodialysis and peritoneal dialysis patients (n=67) during
July-September 2013 at St. Michael’s Hospital (Toronto, Ontario). Twenty-three questions
related to MPF consumption were extracted from the Canadian Diet History Questionnaire II
(DHQ II), from the National Institute of Health, adapted for Canada (Csizmadi et al, 2007). The
FFQ items asked about the frequency, amount and types of MPF consumption. In addition, data
was collected surrounding the purchasing and preparation behaviours, self-reported adherence to
renal diet restrictions, and clinical and demographic data.
Products from each type of commonly consumed MPF categories namely: unbreaded
chicken, ground beef, steak, white fish, beef burgers, deli meats, bacon and shrimp, were
purchased from the top 3 grocery stores in Canada. A concerted effort was made to purchase
store brands and national brands of each type of MPF product. If there were multiple brands,
products that occupied the most shelf space were chosen. In order to further examine the
contribution of additives, comparable reference products were also chosen for each type of MPF
product. A reference product was defined as a fresh MPF item that contained no additional
ingredients or additives. These products were purchased from local butchers or from companies
that could confirm no additives had been added to the product.
A minimum of 150 grams of MPF product was pre-weighed. Foods were cooked
according to package directions. If package directions were not available, foods were cooked
until they reached a safe internal cooking temperature (Government of Canada, 2015). Once
cooked, foods were stored into a re-sealable Ziploc® plastic bag, and kept refrigerated at 5° C
until analysis. All food packaging was retained for labelling information. A product was
considered ‘seasoned’ if the word seasoned was used anywhere on the food package. A product
was considered to contain a phosphorus or potassium additive if such an additive was listed on
48
the ingredient list. Foods sold at a deli, meat or seafood counter in Canada are not required to
have ingredients listed on the consumer package label. Original package information with an
ingredient list was obtained from the deli counter personnel to determine if deli ham contained a
phosphorus or potassium additive. Package information was not available for sole and tilapia
products sold at a seafood counter and therefore the addition of P and K additives for these
products was unknown.
The analyses for the protein, phosphorus, potassium and sodium content of food were
performed by Maxxam Analytics (Mississauga, Ontario). Samples were homogenized, and a
portion was used for nutrient analysis. Protein was analyzed according to the Association of
Analytical Communities (AOAC) official method 992.15 by combustion using TruMacTM
N
(LECO Corporation, St Joseph, MI). The total nitrogen was multiplied by the factor 6.25 to
calculate the protein content. Samples were run in batches and the instrument was corrected for
daily calibration drift. A blank, reference material, EDTA (ethylenediaminetetraacetic acid)
check, and duplicate of a random sample were run for each batch. A CCB (continuous
calibration blank) and CCV (continuous calibration verification) check were also run between
batches.
Phosphorus, potassium and sodium content were determined according to the AOAC
official method 984.27. The samples were digested in a mixture of nitric and hydrochloric acid,
and then analyzed by ICP-OES (inductively coupled plasma - optical emission spectrometry)
using a Thermo Scientific iCAP 6500 ICP instrument (Thermo Fisher Scientific Inc., Waltham,
MA). Samples were run in batches and a daily calibration, blank, matrix spike, duplicate of a
random sample and reference material were run for each batch. A CCB and CCV were also run
between batches. In addition, Maxxam Analytics participates in proficiency testing that
compares inter-laboratory results.
The potassium, phosphorus and sodium contents of each food item are expressed as mg
per 100g of product, while protein is expressed in g per 100g of product. Additionally, the ratio
of milligrams of phosphorus per gram of protein content is reported as the phosphorus to protein
ratio, because of its advantage of being independent from the weight of the food item. Food
categories for which MPF products did not contain an additive were excluded from the analyses
which compared additive, non-additive and reference groups. Comparisons between additive,
49
non-additive and reference groups were determined using Kruskal-Wallis test. If a significant
difference was observed, then Mann-Whitney tests were used for analysis between groups. A
similar approach was used for foods that were labelled seasoned, those not labelled seasoned and
reference foods. Results were considered statistically significant if p < 0.05. All analyses were
done using SPSS version 17.0 (Chicago, IL). The potassium, phosphorus, sodium and protein
content of MPF were compared to the Canadian Nutrient file values and results are reported in
Appendix I.
5.3 Results
Commonly consumed MPF (n=76) in twelve food categories, and comparable reference
foods (n=15) were purchased and chemically analyzed (Table 5.1). Phosphorus additives were
present on the ingredient list in 37% of MPF (Table 5.2), and were highly prevalent in bacon,
deli ham and shrimp products (100%, 73% and 57%, respectively) (Figure 5.1). All phosphorus
additives listed on the ingredient list were a type of sodium phosphate. Potassium additives were
found on the ingredient list in 9% of MPF and found in frozen chicken breast, unbreaded chicken
strips and deli ham products (Table 5.2). The word “seasoned” was found on the package label of
25% of MPF foods, with the majority of seasoned MPF being chicken products (Table 5.2).
Three tilapia and 3 sole products were purchased from the seafood counter where no labelling or
ingredient information was available (Figure 5.1).
Within MPF categories that contained a phosphorus additive (bacon, deli ham, shrimp,
sole, unbreaded chicken breasts, frozen chicken breasts and beef burgers), there was a significant
difference in the sodium, phosphorus and phosphorus to protein ratio among groups (Table 5.3, p
<0.001). No difference was seen in the potassium and protein content between groups. Further
analysis showed that foods listing a phosphorus additive on the ingredient list contained
significantly more phosphorus than foods that did not list a phosphorus additive (Table 5.3, p
<0.05). In addition, foods listing a phosphorus additive had a significantly greater phosphorus to
protein ratio and more sodium than its counterparts without a phosphorus additive and reference
foods (Table 5.3, p <0.05).
In order to gain insight into the extent of the contribution of phosphorus additives to
phosphorus content, we examined foods within MPF categories. Wide variability in phosphorus
content was noted for those foods where phosphorus additives were listed on the ingredient list
50
(Table 5.4). However, the phosphorus to protein ratio appeared to be consistently higher in MPF
foods listing a phosphorus additive compared to foods not listing a phosphorus additive and
reference foods (Table 5.4).
As chicken products contained the largest number of products using the word “seasoned”
on its packaging, only chicken products were included in the analysis of foods labelled seasoned
versus those not labelled seasoned. We found a significant difference in the sodium content
between foods labelled seasoned, foods not labelled seasoned and reference chicken products
(Table 5.5, p = 0.03). Additional analysis indicated that foods labelled seasoned had significantly
more sodium than reference products only (Table 5. 5, p < 0.05). There were no differences in
phosphorus, protein, phosphorus to protein ratio and potassium content among groups.
Among the food groups containing a potassium additive, namely frozen chicken breast,
unbreaded chicken slices and deli ham, there were significant differences in the sodium and
potassium content among foods listing a potassium additive, foods that did not list a potassium
additive and reference foods (Table 5.6, p = <0.05). Between group analyses revealed that foods
listing a potassium additive on the ingredient list had significantly more potassium than foods
without potassium additives and reference foods (Table 5.6, p < 0.05). Foods with and without a
potassium additive listed on the ingredient list had significantly more sodium than reference food
items (Table 5.6, p <0.05). There was a tendency for lower protein content of foods with
potassium additives, however differences were not significantly different. All potassium
additives included in foods were in the form of potassium lactate.
51
Table 5.1 Meat, poultry and fish food categories and comparable reference foods
Food Category n Reference Food n
Chicken Breast, Fresh 5
Chicken Breast 3 Chicken Breast, Frozen 8
Chicken Strips, Packaged 6
Chicken, Rotisserie 5
Ground Beef, Fresh 3 Ground Beef 3
Beef Burgers, Frozen 7
Steak, Fresh 3 Steak 3
Tilapia, Fresh/Frozen† 6 No reference available
Sole, Fresh/Frozen† 7 No reference available
Shrimp, Frozen 7 Shrimp 1
Deli Ham, Packaged 11 Pork Leg 2
Bacon, Packaged 8 Pork Belly 3
A reference product was defined as a fresh MPF item that contained no additional ingredients or
additives. Reference products (n=15) were purchased from local butchers or from companies that
could confirm no additives had been added to the product.
52
Table 5.2 Characteristics of meat, poultry and fish (MPF) products commonly consumed
by patients with chronic kidney disease (n=76)
MPF Category n
Contains
Phosphorus
Additives
Contains
Potassium
Additives
Labelled
Seasoned
Seafood /
Meat/Deli
Counter
n (%)
Chicken
Chicken Breast,
Fresh 5 0 (0) 0 (0) 0 (0) 0 (0)
Chicken Breast,
Frozen 8 2 (25) 1 (13) 8 (100) 0 (0)
Chicken,
Unbreaded
Strips, Packaged
6 2 (33) 2 (33) 3 (50) 0 (0)
Chicken,
Rotisserie 5 0 (0) 0 (0) 4 (80) 5 (100)
Beef
Ground Beef,
Fresh 3 0 (0) 0 (0) 0 (0) 0 (0)
Steak, Fresh 3 0 (0) 0 (0) 0 (0) 0 (0)
Beef Burgers,
Frozen 7 1 (14) 0 (0) 1 (14) 0 (0)
White Fish
Tilapia,
Fresh/Frozen† 6 0 (0) 0 (0) 0 (0) 3 (50)
Sole,
Fresh/Frozen† 7 3 (43) 0 (0) 0 (0) 3 (43)
Shrimp
Shrimp, Frozen 7 4 (57) 0 (0) 0 (0) 1 (14)
Processed Meat
Deli Ham 11 8 (73) 4 (36) 3 (27) 5 (46)
Bacon 8 8 (100) 0 (0) 0 (0) 0 (0)
*Alternate brand is national brand
† Tilapia (n=3) and Sole (n=3) purchased from the seafood counter do not include a list of
ingredients and it was unknown if these products contained phosphorus additives
53
Figure 5.1 Percent of MPF foods containing phosphorus additives on the ingredient list
according to MPF category (descending order)
Tilapia (n=3) and sole (n=3) purchased from the seafood counter do not include/require a list of
ingredients and it was unknown if these products contained phosphorus additives
54
Table 5.3 Comparison of analyzed nutrients content among MPF categories containing
phosphorus additives, without phosphorus additives and reference foods§
Reference
n=12
P additives
n=28
No P additives*
n= 26
Median (min,
max)
Median (min,
max)
Median (min,
max) p-value
†
Sodium
62 (41, 290)a 935 (200, 2800)
b 485 (130, 1100)
c < 0.001
Potassium
375 (66, 450) 295 (10, 1100) 305 (52, 920) 0.88
Phosphorus
210 (100, 260)a 270 (140, 500)
b 200 (130, 510*)
a < 0.001
Protein
23 (13, 29) 18 (12, 49) 20 (13, 30)
0.47
Phosphorus:Protein
8.7 (7.2, 9.3)a 12.5 (8.6, 19.9)
b 9.5 (7.4, 27.9)
c < 0.001
§Food groups containing phosphorus additives: Frozen chicken breast, unbreaded chicken strips,
beef burgers, sole, shrimp, deli ham and bacon
Abbreviation: P = Phosphorus
Phosphorus, Sodium, Potassium were analyzed and reported as mg/100g. Protein is analyzed and
reported as g/100mg. Phosphorus:Protein ratio is reported as mg P/g protein.
abc Medians significantly different by Mann-Whitney and p<0.05 if subscripts differ from each
other
†Kruskal-Wallis test
*includes foods from seafood counter where an ingredient list was not available
.
55
Table 5.4 Analyzed nutrient content of MPF categories with and without phosphorus
additives listed on the ingredient list and reference foods
Food Group Data Source n P Pro P:Pro Na K
Bacon†† P Additives 8 301 (115) 31 (11) 9.7 (0.8) 1625 (658) 355 (133)
Reference 3 123 (32) 17 (4) 7.4 (0.2) 71 (9) 233 (68)
Deli Ham†
P Additives 8 264 (33) 16 (2) 17.1 (3.2) 999 (67) 543 (346)
No P Additives 3 217 (29) 18 (5) 13 (5.9) 977 (21) 573 (287)
Reference 2 195 (64) 23 (8) 8.5 (0.1) 51 (1) 345 (106)
Shrimp,
Fresh/Frozen
P Additives 4 198 (57) 14 (2) 14.5 (4.5) 420 (67) 31 (21)
No P Additives 3 200 (82) 17 (3) 12 (5) 630 (61) 94 (56)
Reference 1 130 16 7.9 290 66
Sole,
Fresh/Frozen
P Additives 3 267 (25) 17 (3) 15.8 (1.7) 310 (106) 168 (79)
No P Additives* 4 290 (150) 16 (1) 17.3 (7.5) 295 (135) 152 (75)
Chicken strips,
unbreaded
P Additives 2 290 (14) 23 (1) 12.5 (0.1) 430 (42) 715 (544)
No P Additives 4 195 (19) 23 (1) 8.7 (0.9) 488 (147) 470 (194)
Reference 3 247 (15) 27 (2) 9.0 (0.2) 54 (12) 427 (25)
Chicken
breast, Frozen
P Additives 2 335 (35) 26 (4) 13.3 (3.6) 445 (346) 445 (35)
No P Additives 6 212 (22) 26 (2) 8.2 (1) 420 (55) 435 (243)
Reference 3 247 (15) 27 (2) 9.0 (0.2) 54 (12) 427 (25)
Beef Burger,
Frozen
P Additives 1 210 17 12.1 340 300
No P Additives 6 178 (29) 18 (4) 9.9 (1.1) 485 (54) 295 (54)
Reference 3 223 (25) 24 (3) 9.3 (0.1) 68 (14) 400 (50)
Tilapia,
Fresh/Frozen No P Additives* 6 205 (14) 20 (2) 10 (0.5) 58 (37) 390 (51)
Chicken
Breast, Fresh
No P Additives 5 260 (23) 28 (1) 9.2 (0.5) 56 (11) 444 (43)
Reference 3 247 (15) 27 (2) 9.0 (0.2) 54 (12) 427 (25)
Chicken,
Rotisserie
No P Additives 5 200 (12) 27 (1) 7.5 (0.5) 306 (90) 360 (26)
Top Sirloin
Steak, Fresh
No P Additives 3 270 (12) 31 (3) 8.7 (0.5) 66 (9) 460 (25)
Reference 3 263 (6) 30 (2) 8.7 (0.5) 63 (8) 460 (26)
Lean Ground
Beef, Fresh
No P Additives 3 203 (6) 23 (1) 8.9 (0.6) 71 (2) 367 (21)
Reference 3 223 (25) 24 (3) 9.3 (0.1) 68 (14) 400 (50)
Notes: No reference product available for Tilapia and Sole
Values for analyzed and reference foods are expressed as Mean (Standard Deviation)
P, Na, K were analyzed and reported as mg/100g. Pro is analyzed and reported as g/100mg. P:Pro
ratio is reported as mg P/g protein.
Abbreviations: Na = Sodium, K = Potassium, P = Phosphorus, Pro = Protein; P:Pro Ratio = Phosphorus to
protein ratio
†Reference product for deli ham is unprocessed pork leg
††Reference product for bacon is unprocessed pork belly
*Tilapia (n=3) and sole (n=3) purchased from the seafood counter do not include a list of ingredients and
it was unknown if these products contained phosphorus additives
56
Table 5.5 Comparison of analyzed nutrient content among chicken products labelled
seasoned, products not labelled seasoned and reference products
Reference
n=3
Labelled
Seasoned*
n=15
Not Labelled
Seasoned
n=9
Median (min,
max)
Median (min,
max)
Median (min,
max)
p-value†
Sodium 58 (41, 63)a
400 (200, 690)b
75 (49, 610)ab
0.03
Potassium 430 (400, 450) 370 (300, 1100) 420 (310, 490) 0.65
Phosphorus 250 (230, 260) 210 (190, 360) 240 (180, 290) 0.64
Protein 28 (26, 28) 25 (22, 30) 27 (22, 29) 0.41
Phosphorus:Protein 8.9 (8.8, 9.2) 8.0 (7.3, 15.8) 8.9 (6.9, 9.8) 0.64
*A product was considered ‘seasoned’ if the word seasoned was used anywhere on the food package abc
Medians significantly different by Mann-Whitney and p<0.05 if subscripts differ from each other
†Kruskal-Wallis test
Phosphorus, Sodium, Potassium, were analyzed and reported as mg/100g. Protein is analyzed and
reported as g/100mg. Phosphorus : Protein ratio is reported as mg P/g protein.
Table 5.6 Comparison of analyzed nutrient content among MPF foods containing
potassium additives, not containing potassium additives and reference foods§
Reference
n=5
K additives
n=7
No K additives
n= 18
Median (min,
max)
Median (min,
max)
Median (min,
max) p-value
†
Sodium 52 (41, 63)a
930 (280, 1100)b
590 (200, 1100)b
0.002
Potassium 420 (270, 450)a
900 (750, 1100)b
325 (260, 470)a
<0.001
Phosphorus 240 (150, 260) 270 (190, 300) 215 (190, 360) 0.32
Protein 28 (18, 29) 17 (13, 25) 23 (13, 30) 0.06
Phosphorus:Protein 8.8 (8.4, 9.2) 17.6 (7.7, 19.8) 9.7 (7.4, 19.9) 0.09
abc Medians significantly different by Mann-Whitney and p<0.05 if subscripts differ from each other
†Kruskal-Wallis test §Food groups containing potassium additives: Frozen chicken breast, unbreaded chicken slices, and deli
ham
Phosphorus, Sodium, Potassium, were analyzed and reported as mg/100g. Protein is analyzed and
reported as g/100mg. Phosphorus : Protein ratio is reported as mg P/g protein.
57
5.4 Discussion
Our study demonstrated that phosphorus and potassium additives significantly contribute
to the phosphorus and potassium content of MPF in Canada. Generally, foods that were frozen,
packaged or processed, such as frozen chicken breasts, unbreaded chicken strips and deli ham
were more likely to contain additives compared to fresh MPF. Products labelled as “seasoned”
surprisingly did not contain significantly more phosphorus than those not labelled as seasoned.
MPF foods with a phosphorus additive listed on the ingredient list contain a higher
amount of phosphorus and greater phosphorus to protein ratio than foods that do not list a
phosphorus additive. In MPF types containing products with and without additives (excludes
sole products), the higher phosphorus content of foods with phosphorus additives ranged from -
1% to 58%, with a mean increase of 29%. Our results are in line with existing literature from the
U.S and Europe, which have reported a 30-60% increase in phosphorus in additive-containing
foods (Léon JB et al, 2013; Cupisti et al, 2012; Benini et al, 2011; Sherman et al, 2009ab;
Sullivan et al, 2007). Food regulations in the U.S and Canada are similar, as they both allow
phosphorus additives to be added to meat and poultry products in amounts up to 0.5% of the
product formula (CFIA 2013; FSIS 2015). However, there is no maximum limit for the use
phosphorus additives in fish and seafood products in the United States, while the maximum use
in Canada is 0.5% (CFIA 2013, FDA 2014b). As all phosphorus additives were in the form of
sodium phosphate, there was significantly more sodium in MPF foods containing a phosphorus
additive. This study supports educating patients to avoid foods containing a phosphorus additive
on the ingredient list, especially given that it is a highly bioavailable form of phosphorus.
Furthermore, such intervention was previously shown to result in statistically significant
decreases in serum phosphorus concentrations (Sullivan et al, 2009).
While almost all food products contained an ingredient list, there were six fish products
that were purchased from a seafood counter where a list of ingredients was not available.
Therefore, we were unable to ascertain if these products contained phosphorus additives. As we
recognized that patients may assume these fresh seafood products do not contain additives, we
included the products in the analysis as “no phosphorus additive” foods. However, one sole
product had the highest phosphorus content and phosphorus to protein ratio of all foods
analyzed, (510 mg P/100g and 27.9 mg P/g Pro, respectively) and is therefore highly likely to
58
contain phosphorus additives. It has been revealed that sodium compounds may come into
contact with fish and seafood products during the commercial processing before they are sold in
retail stores (Ahuja et al, 2015). Hence, it would be prudent for patients to be aware and
informed of the potential of additives from fresh fish at a seafood counter.
Renal dietitians educate patients with CKD to avoid seasoned products, as these foods
may include phosphorus additives (ORN, 2013; Sherman & Mehta, 2009b). In our study, no
differences in the phosphorus content were noted in chicken products labelled as ‘seasoned’
compared to those that were not labelled as seasoned. According to the Canadian Food
Inspection Agency (CFIA), the term ‘seasoned’ reflects a solid cut of meat that contains one of:
phosphate salts; phosphate salts and water; or spices and water. Therefore, the term ‘seasoned’ is
not synonymous with phosphorus additives. Only 4 of 15 products labelled ‘seasoned’ contained
a phosphorus additive, so it is possible that the other products contained spices and water which
did not add to the phosphorus content of the food. Injection of solutions into poultry is common
and is estimated to occur in 30% of chicken products in the U.S (Ahuja et al, 2015). Sherman &
Mehta (2009b) measured the phosphorus content of 36 uncooked meat and poultry products and
determined that enhanced products contained a higher phosphorus to protein ratio. Notably, the
authors indicated that 39% of enhanced products listed a phosphorus additive which is a higher
percentage compared to our results. ‘Seasoned’ products contained higher amounts of sodium
than reference MPF foods, and therefore, those patients requiring a dietary sodium restriction
should be educated to choose fresh MPF without additives and avoid ‘seasoned’ poultry.
However, in Canada, dietitians should re-consider the impact of educating patients to avoid
‘seasoned’ chicken products as part of a low phosphorus diet, given our findings. Our study
shows that it would be more effective to educate patients requiring a phosphorus restricted diet to
avoid foods with a phosphorus additive listed on the ingredient list.
The higher amount of potassium in MPF foods listing a potassium additive compared to
those without potassium additives was remarkable. While there was a wide range in the
potassium content of foods containing a potassium additive, two of the products analyzed
contained 1100 mg of potassium per 100g. This a concerning amount of potassium, especially
for patients with CKD requiring a potassium restriction, as this amount contributes to more than
half of their daily recommended intake of less than 2000 mg of potassium (Nelms et al, 2007). In
addition, patients with impaired urinary potassium excretion such as those with heart failure,
59
diabetes and those taking angiotensin converting enzyme inhibitors and angiotensin receptor
blocker medications are at increased risk of life-threatening hyperkalemia (IOM, 2005) and may
be unaware of the potential high potassium content of these foods. We have determined that
sodium reduced foods that listed a potassium additive on the ingredient list had on average, more
than double the amount of potassium compared with sodium reduced foods that did not list a
potassium additive (713 mg/100g versus 350 mg K/100g) (Sharma Parpia et al, 2014, Chapter 6).
We attribute the large increase in potassium content to the fact that potassium lactate, the type of
potassium additives found in analyzed products is allowed as an antimicrobial agent up to 4% in
meat and poultry products in Canada, and 4.8% in the U.S. (Health Canada, 2012b; FSIS, 2012).
This is considerably greater than the allowable amount of phosphorus additives (0.5%), therefore
potassium lactate may have a greater potential to contribute to the potassium content of meat and
poultry products.
While previous studies have examined the contribution of phosphorus and potassium
additives to the nutrient content of foods, this is the first study to chemically analyze foods for
this purpose in Canada. Strengths of our study include that a representative sample of foods were
chosen for analysis and were relevant to the food consumption and preparation habits of patients
with CKD. In addition, we included additive-free reference foods which acted as a control for
possible mislabelling of MPF products. However, this is a cross sectional study that is only
applicable to the study time period as food products are often reformulated. As new phosphorus
and potassium additives are continuously being approved for use in various types of food, it is
likely that the contribution of potassium and phosphorus from additives will increase over time.
While efforts were made to choose store and national brands, products were purchased from
Toronto, Ontario, where the food supply may be different than other geographical regions.
In conclusion, MPF foods with a phosphorus and/or potassium additive on the ingredient list
significantly contributes to the phosphorus and potassium content of the food. Patients with CKD
should be educated to avoid MPF foods containing a phosphorus additive, and particularly
potassium additives where there is a marked increase in potassium content from potassium
lactate. In Canada, we found the term ‘seasoned’ does not always imply the food item contains
phosphorus additives or higher phosphorus content, but does contain high amounts of sodium. In
addition, patients should be cautious when purchasing fish and seafood from a counter as these
foods do not contain an ingredient list and may contain additives. Generally, MPF foods that
60
were fresh were least likely to contain additives. Therefore, encouraging consumption of fresh
MPF products may lead to improved dietary compliance in patients with CKD.
61
6.0 Do Sodium Reduced Meat and Poultry Products Contain a Significant
Amount of Potassium and Phosphorus from Additives?
This manuscript has been submitted to the Clinical Journal of the American Society of
Nephrology for publication: Parpia AS, Goldstein MB, Arcand J, L’Abbé MR, Darling PB.
Sodium Reduced Meat and Poultry Products Contain a Significant Amount of Potassium from
Additives
This study was presented in part at the American Society of Nephrology Kidney week,
Philadelphia, PA, November 11-16, 2014. The abstract was published in the Journal of the
American Society of Nephrology. 2014; 25:685A
6.1 Introduction
The reduction of sodium in processed foods is a key component of population-wide
health strategies being implemented by various countries in an effort to reduce the sodium intake
of individuals (Mohan et al, 2009). Current American and Canadian recommendations are that
food manufacturers lower the sodium content of their food products (Henney et al, 2010; Health
Canada, 2010). As sodium chloride acts to preserve and enhance the taste and texture of meat
and poultry products (MPP), food manufacturers may use phosphorus and potassium additives to
replace the functional and flavor properties of sodium chloride (Verma & Banerjee, 2012).
Phosphorus additives are increasingly being added to MPP as they increase shelf-life,
retain moisture, maintain color and improve texture (Kalantar-Zadeh et al, 2010; Murphy-
Gutekunst & Uribarri, 2005). Studies have demonstrated that phosphorus additives significantly
contribute to the dietary phosphorus load which can contribute to hyperphosphatemia and its
respective complications in patients with chronic kidney disease (CKD) (Benini et al, 2011;
Carrigan et al, 2014; Leon et al, 2013; Sullivan et al, 2007; Sherman & Mehta, 2009ab; Bell et
al, 1977).
Potassium additives, such as, potassium chloride, confer a salty taste and are often used
for sodium replacement in sodium reduced foods (Dotsch et al, 2009). Potassium lactate and
potassium phosphate have the added benefits of improving shelf-life and moisture retention in
MPP (Verma & Banerjee, 2012; Desmond, 2006; Ruuseunen et al, 2002; Health Canada, 2014).
While evidence suggests that a diet high in potassium from fruits, vegetables and low-fat dairy is
62
associated with a significant blood pressure lowering effect (Sacks et al, 2001) and may be
advantageous to the general population (Salehi-Abargouei et al, 2013), an increased potassium
load from additives could potentially contribute to hyperkalemia and fatal arrhythmias in patients
with CKD. Life-threatening hyperkalemia due to use of potassium containing salt substitutes has
been reported to affect individuals with impaired renal excretion, as well as patients with heart
disease (Doorenbos & Vermeij, 2003; John et al, 2011). The risk of hyperkalemia is further
increased with the use of medications such as angiotensin-converting enzyme inhibitors,
angiotensin II receptor blockers and potassium-sparing diuretics, especially when taken
concomitantly with salt substitutes (Ray et al, 1999).
Patients with CKD are educated to restrict sodium intake, which includes choosing low
sodium alternatives (NKF, 2015). Due to the possible inclusion of phosphorus and potassium
additives as a sodium replacer, it is unclear if sodium reduced foods are suitable for inclusion in
a renal diet. Currently, the phosphorus and potassium content of packaged foods are not included
on the Nutrition Facts table. Thus it is difficult for patients and health care providers to assess the
contribution of additives to the intake of those nutrients in order to make appropriate food
choices. The primary objective of this study was to determine whether and to what extent the
reduction of sodium in MPP is associated with increased amounts of potassium and phosphorus
from food additives.
6.2 Materials and Methods
This was a cross-sectional study of MPP selected for chemical analysis. Stores from the
top three grocery store chains in Canada were scanned for all sodium reduced MPP in May 2014.
An inclusive sample of all sodium reduced products with a corresponding original non-sodium
reduced counterpart (n=38) were selected. We considered a product to be sodium reduced if the
package label had a nutrient content claim stating the percentage reduction in sodium (eg. “25%
less sodium than our original product”). The “original product” of the same brand, but without
the sodium reduction claim was selected as the original non-sodium reduced counterpart. In
addition, reference foods were used in order to act as a control and to gain insight into the
magnitude to which additives contribute to the phosphorus and potassium content of the food.
The two types of reference foods were: 1) non-packaged additive-free reference foods (Ref-0)
(n=5) and 2) packaged potassium and phosphorus additive-free reference foods (Ref-KP)
63
(n=8).The fresh, Ref-0 foods were purchased from local butchers and contained no additional
ingredients or additives. The Ref-KP foods were processed MPP that were labeled as being
“Made with natural ingredients. No preservatives added”. While these products did not have any
potassium or phosphorus additives on the ingredients list, they did contain other additives, such
as sodium.
A minimum of 200 grams of product was cooked according to package directions, stored
into a re-sealable Ziploc® plastic bag, and kept at 5° C until analysis. All original food packages
were retained for labeling information. Protein, phosphorus, potassium and sodium were
analyzed by Maxxam Analytics (Mississauga, Ontario). Samples were homogenized and a
portion was used for nutrient analysis.
Protein was analyzed according to the Association of Analytical Communities (AOAC)
official method 992.15 by combustion using TruMacTM
N (LECO Corporation, St Joseph, MI).
The total nitrogen was multiplied by the factor 6.25 to calculate the protein content. Samples
were run in batches and the instrument was corrected for daily calibration drift. A blank,
reference material, EDTA (ethylenediaminetetraacetic acid) check, and duplicate of a random
sample were run for each batch. A CCB (continuous calibration blank) and CCV (continuous
calibration verification) check were also run between batches.
Phosphorus, potassium and sodium content were determined according to the AOAC official
method 984.27. The samples were digested in a mixture of nitric and hydrochloric acid, and then
analyzed by ICP-OES (inductively coupled plasma - optical emission spectrometry) using a
Thermo Scientific iCAP 6500 ICP instrument (Thermo Fisher Scientific Inc., Waltham, MA).
Samples were run in batches and a daily calibration, blank, matrix spike, duplicate of a random
sample and reference material were run for each batch. A CCB and CCV were also run between
batches. In addition, Maxxam Analytics participates in proficiency testing that compares inter-
laboratory results.
The potassium, phosphorus and sodium contents of each food item were expressed as mg
per 100g of product, while protein was expressed in g per 100g of product. Additionally, the
ratio of mg of phosphorus per g of protein content is reported as the phosphorus to protein ratio,
with the advantage of its independence from the size of the food serving (K/DOQI, 2003).
Results are summarized as mean and standard deviation. Differences between the original and
64
sodium reduced MPP were determined using paired t-test. Comparisons between original,
sodium reduced and reference foods groups were determined using one-way anova. If a
significant difference was observed, then t-tests were used for analysis between groups. Results
were considered significant at p<0.05. All analyses were done using SPSS version 17.0
(Chicago, IL).
6.3 Results
Sodium reduced MPP (n=19) contained on average 44% more potassium (mg/100g)
compared with their original non-sodium reduced counterparts, with an average difference of
184 mg/100g (95% confidence interval (CI): 90-279; p< 0.001) (Table 6.1). There was 38% less
sodium in products that had been sodium reduced compared to original counterparts, with an
average difference of 486 mg/100g (95% CI: 334-638; p <0.001). The difference in the amounts
of phosphorus and protein was not statistically significant. The original non-sodium reduced
foods had a slightly higher (p=0.009) phosphorus to protein ratio.
Table 6.2 compares mean values of reference foods with sodium reduced and original
MPP. There was an overall significant (p<0.05) difference in the sodium, potassium, phosphorus
and phosphorus to protein ratio among groups. Between group analysis revealed that REF-0
products had significantly less (p<0.05) sodium, compared to the sodium reduced MPP, original
non-sodium reduced, and REF-KP products. The REF-KP products had similar amounts of
phosphorus and potassium as REF-0 products, however these products contained significantly
higher sodium (p<0.05). Both REF-0 and REF-KP products contained significantly less (p<0.05)
phosphorus and potassium compared to sodium reduced foods (Table 6.2).
Further detail on individual products, including the presence of additives and sodium
claims, is shown in Table 6.3. The potassium content of sodium reduced products ranged from
210-1500 mg. Potassium containing additives were found on the ingredient list in 63% of the
sodium reduced products and in only 25% of the non-sodium reduced products (p = 0.02). Mean
potassium content of sodium reduced products with a potassium additive listed on the ingredient
list was 713 mg/100g versus 320 mg K/100g in sodium reduced foods without listed potassium
additives (p=0.002). In contrast, phosphorus-containing additives, such as sodium phosphate,
were found on the ingredient list in 68% of sodium reduced products and 95% of original non-
65
sodium reduced products. There was a 21% increase in the use potassium phosphates in sodium
reduced products (Table 6.3 and Figure 6.1).
Table 6.1 Comparison of analyzed nutrient levels in paired sodium reduced and original (non-
sodium reduced) meat and poultry products
Na, K, and P are measured in mg/100g. Protein is measured in g/100mg. Phosphorus to protein
ratio is measured in mg P/g protein.
Abbreviation: Na = Sodium; K = Potassium; P = Phosphorus; SD = standard deviation; CI =
Confidence Interval
Value expressed at Mean (SD), unless noted otherwise.
Statistical analyses comparing matched pairs of original and Na-reduced meat and poultry
products were done using paired t-tests. p <0 .05 was considered statistically significant.
Nutrient Na -Reduced
(n=19)
Original
(n=19)
Mean Paired
Difference
(95% CI)
p-value Mean Percent
Change
Na 749 (299) 1236 (548) -486 (-638, -334) < 0.001 ↓ 38 (11)
K 568 (334) 383 (173) 184 (90, 279) 0.001 ↑ 44 (43)
P 253 (75) 265 (87) -13 (-34, -8) 0.20 ↓ 3 (16)
Protein 25 (9) 23 (9) 1 (0.8, 3) 0.26 ↑ 6 (18)
P:Protein
ratio
10.8 (2.6) 11.5 (3.0) -1.1 (-1.9, -0.3) 0.009 ↓ 8 (13)
66
Table 6.2 Comparison of sodium reduced, original (non-sodium reduced), and reference meat
and poultry products
Nutrient
Reference-0
(n=10)
Reference - KP
(n=8)
Original
(n=18)
Na-Reduced
(n=19) p-value
†
Na
60 (11)a
866 (215)bc
1235 (577)c
749 (299)b
< 0.001
K
342 (96)a
384 (64)a
383 (173)a
568 (334)b
0.03
P
193 (60)b
188 (33)ab
265 (87)c
254 (75)dc
0.02
Protein
24 (6)
22 (5) 24 (9) 24 (9) 0.94
P:Protein
Ratio
8.1 (0.7)c
8.5 (0.8)ac
11.5 (3.0)d
10.8 (2.7)bd
0.001
Na, K, and P are measured in mg/100g. Protein is measured in g/100mg. Phosphorus to protein
ratio is measured in mg P/g protein.
abcd Medians significantly different by independent t-test and p<0.05 if subscripts differ from
each other
†One-way anova test
Abbreviation: Na = Sodium; K = Potassium; P = Phosphorus; SD = standard deviation; CI =
Confidence Interval; Ref-0 = Additive-free reference food; Ref-KP = Potassium and phosphorus
additive-free reference food
Value expressed at Mean (SD), unless noted otherwise.
67
Table 6.3 Chemical analysis of sodium, potassium, phosphorus and protein content of paired original (non-sodium reduced) and
sodium-reduced meat and poultry products
# Original (Non-Sodium Reduced) Sodium-Reduced
Original Product Na K P Pro PO4
AdditivesListed
K Additives
Listed Sodium Reduced Product Na K P Pro
PO4 Additives
Listed
K Additives
Listed
Reduction in Na (%)
Change in K (%)
1 President's Choice
Extra Lean Stone Roasted Ham 950 320 270 18 Y N
45% less sodium than PC Traditional Black Forest Ham
560 520 270 22 Y Y 41 +63
2 President's Choice
Stone-Roasted Ham Rosemary & Black Pepper
950 320 270 18 Y N 45% less sodium than PC
Traditional Black Forest Ham 620 600 310 22 Y Y 35 +88
3 President's Choice
Oven Roasted Turkey Breast 770 450 260 19 Y Y
55% less sodium than PC Oven Roasted Turkey Breast
460 950 260 22 Y† Y† 40 +111
4 President's Choice Tomato and Basil
Oven Roasted Turkey Breast 770 450 260 19 Y Y
30% less sodium than PC oven roasted turkey breast
550 800 240 19 Y Y 29 +78
5 President's Choice
Oven Roasted Chicken Breast 760 420 240 19 Y Y
40% less sodium than PC oven roasted chicken breast
550 520 290 21 Y Y 28 +24
6 Schneider's Olde Fashioned Fully Cooked Smoked Ham
1000 910 270 17 Y Y 25% less sodium than our
regular Olde Fashioned Ham 600 1500 200 18 Y† Y† 40 +65
7 Maple Leaf
Flakes of Ham (canned) 940 280 230 17 Y N
33% less sodium that our regular flakes of ham
590 260 220 18 Y N 37 -7
8 Maple Leaf Top Dogs
1200 540 260 14 Y Y 25% less salt than our original 790 850 210 13 Y† Y† 34 +57
9 President's Choice
Breakfast Sandwich Pork Sausage
830 310 170 20 N N 30% less sodium that PC breakfast sandwich pork
sausage 610 410 220 26 N N 27 +32
10 President's Choice
Naturally Smoked Bacon 1500 350 300 32
Y
N 50% less salt than regular PC
bacon 1200 340 320 30 Y N 20 -3
11 No Name
Mild Sugar Cured Bacon 1500 240 170 18 Y N
50% less salt that no name bacon
770 210 150 19 Y N 49 -13
12 Maple Leaf
Bacon 1200 290 260 27 Y N
33% less salt than our regular bacon
490 270 250 27 Y N 59 -7
13 Schneider's
Naturally smoked bacon 800 230 280 26 Y N
40% less salt per 50g serving than our regular bacon
400 500 180 24 Y Y 50 +117
14 Irresistibles
Bacon 1100 220 150 17 Y N
40% less salt than selection bacon
840 370 170 28 N N 24 +68
68
15 Selection
Bacon 1100 220 150 17 Y N
50% less salt than regular selection bacon
840 210 140 16 Y Y 24 -5
16 President's Choice
Fully Cooked Bacon 2300 470 380 35 Y N
50% less salt than PC fully cooked bacon
1000 380 330 33 Y N 56 -19
17 Maple Leaf
Fully Cooked Bacon 1800 470 370 41 Y N
50% less salt than our regular fully cooked bacon
1100 740 390 48 Y Y 39 +57
18 Compliments
Naturally Cooked Fully Cooked Bacon
2800 570 500 49 Y N 50% less salt than our
compliments fully cooked bacon 1600 1000 410 43 Y Y 43 +75
19 Butterball
Bacon Style Turkey 1200 230 280 20 Y N
50% less salt than our original bacon style turkey
660 360 260 18 Y† Y† 45 +57
Abbreviation: Na = Sodium; K = Potassium; P = Phosphorus; Pro = Protein
Values for sodium, potassium, phosphorus are reported in mg/100g. Values for protein are reported in g/100g. †Includes a potassium phosphate additive (i.e.potassium phosphate, potassium pyrophosphate) in the ingredient list on product label
69
Figure 6.1 Presence and type of additives in original and sodium reduced meat and poultry
products (MPP)
Note: Phosphorus Additives and Potassium Additives groups exclude foods listing potassium
phosphate on the ingredient list
0
10
20
30
40
50
60
70
80
90
100
PhosphateAdditives
PotassiumAdditives
PotassiumPhosphate*
% o
f M
PP
conta
inin
g a
dditiv
es
Original (n=19)
Sodium-Reduced (n=19)
70
6.4 Discussion
We demonstrate significantly greater amounts of potassium in sodium reduced meat and
poultry foods. The higher potassium content is due to the increased prevalence of potassium
additives, such as potassium chloride, potassium lactate, and potassium phosphate, which
manufacturers are likely using as a sodium replacer. The wide variability in potassium content
was remarkable, for example one sodium reduced product contained 1500 mg of potassium in a
typical serving (100g or 3.5oz) of cooked meat product. This amount is 75% of the
recommended daily intake of potassium for an individual with moderate to severe kidney disease
(Nelms et al, 2007) and is equivalent to taking approximately two doses of the 20mEq potassium
chloride supplement, K-Dur® (K/DOQI, 2004). This is of concern as an oral potassium load such
as this can produce a significant increase in serum potassium (Allon et al, 1993; Fernandez et al,
1986) in patients with end-stage renal disease, and along with usual dietary potassium intake
from other food sources, may subsequently lead to hyperkalemia which is associated with
arrhythmias and sudden cardiac death (Sanghavi et al, 2013). In one study by Noori et al (2010),
higher dietary potassium intake was associated with increased mortality in patients on
hemodialysis. Furthermore, as meat and poultry is not commonly considered as a high potassium
food source, it would be very difficult for the patient with hyperkalemia and health care team to
identify the source of dietary potassium.
Patients are often educated to select lower sodium foods, and may perceive sodium
reduced foods as being advantageous without realizing the potential for higher potassium content
in these foods. Sodium reduced products with a potassium additive listed on the ingredients list
contained, on average, more than double the amount of potassium compared to products with no
potassium additives on the ingredients list. Currently, product label information on potassium
content is available for less than 10% of packaged food products in the United States (Curtis et
al, 2013). More recently, the Health Canada and U.S. Food and Drug Administration have both
proposed that potassium be included in future Nutrition Facts tables on all packaged products,
which would provide important information to help guide those who need to limit dietary
potassium.
Interestingly, there was no difference in the phosphorus content between the sodium
reduced and original formulations of food products. This is likely due in part to the fact that
71
phosphorus additives were more prevalent in original non-sodium reduced products (95%) than
sodium-reduced products (68%). In several products, manufacturers replaced sodium phosphate
with a potassium phosphate additive in order to reduce the sodium in the product, resulting in a
21% increase in the use of potassium phosphates in sodium reduced products. This is not entirely
surprising, as five of the 11 phosphate salts approved for use in the United States are potassium
salts (Sherman & Mehta, 2009b). We therefore attribute the increase in potassium and
unchanged phosphorus in these sodium reduced products to the substitution of phosphorus
additives by potassium additives.
Although the REF-KP products were lower in potassium and phosphorus, they were as
high in sodium as the original non-sodium reduced product and thus are not appropriate for
patients needing to follow a renal diet. Choosing the Ref-0, non-packaged additive-free fresh
version of the meat and poultry in its unprocessed or unaltered state would be considered the best
option with regards to potassium, phosphorus, phosphorus to protein ratio and sodium content.
However, issues such as lack of convenience, lack of cooking skills and the complexity of the
renal diet remain large barriers to diet adherence in this population (Wright & Cavanaugh, 2010;
Venegoor, 2009; Moubarac et al, 2014).
There are few published data on the potassium content of foods. Sherman & Mehta
(2009b) measured the potassium content of 36 uncooked MPP and found that enhanced products,
injected with a sodium and additive-containing solution, contained 8.7% more potassium than
regular (non-enhanced) products. Our results are in line with those published by Sherman &
Mehta (2009b) as they also noted that there was marked variability in potassium content, with
the potassium content of enhanced MPP ranging from 170 to 930 mg/100g.
While no other study to our knowledge has chemically analyzed the potassium content in
sodium reduced MPP, Jaffery & Hood (2006) compared the phosphorus content in low sodium
and regular sodium foods obtained from the USDA food composition tables. He reported no
difference in phosphorus content in the majority (68%) of products measured.
It should be noted that our study is a cross-sectional analysis of MPP obtained from one
geographical area. Although many of the foods analyzed were national brands, the formulation
of these products can change over time, thus altering the nutritional content.
72
In conclusion, potassium additives are frequently added to sodium reduced meat and
poultry products in amounts that significantly contribute to the potassium load for patients with
chronic kidney disease and others with impaired renal excretion of potassium. Patients requiring
a potassium restriction should be educated to avoid sodium reduced meat and poultry products.
Our results support the inclusion of potassium content as a mandatory component on food
labeling to potentially decrease the risk of life-threatening hyperkalemia from sodium reduced
foods in vulnerable populations.
73
7.0 Overall Discussion & Conclusions
We have identified that the most commonly consumed meat, poultry and fish products
among patients on dialysis in Toronto, Canada were chicken, ground beef, steak, white fish, beef
burgers, shrimp, deli ham, and bacon. Participants generally chose a fresh version of MPF
products in accordance with a low sodium diet. The majority of patients (78%) also reported
checking for sodium on the Nutrition Facts table. However, they consumed certain types of high-
sodium processed MPF products frequently, such as bacon and deli ham. Likewise, a recent
study among CKD patients in England demonstrated that 87% of patients reported consumption
of tinned or processed meats at least once per week (Nerbass et al, 2014).
This was the first study to our knowledge to specifically examine the types of MPF foods
most commonly consumed among the dialysis population. As these patients are educated to
increase consumption of high biological value protein, it is valuable for health care providers to
gain an understanding of their intake patterns. Previous studies that have examined dietary intake
in the CKD population differ from our study findings as they have ranked food sources more
generally according to percent of energy intake or to a specific nutrient intake such as fatty acid.
In addition, their study population resided in a different geographical region (Khoueiry et al,
2011; Fasset et al, 2007; Kalantar-Zadeh et al, 2002). While it has been shown that animal
protein contributes to 46% of total protein intake (Pasiakos et al, 2015), it is important to note
that our FFQ did not assess intake of plant protein, dairy or egg intake. The results of Study 1
add to our current understanding of the dietary intake and food consumption behaviours of
patients with end-stage renal disease (ESRD) in Canada. Furthermore, the results enabled us to
select relevant MPF foods that our patients with ESRD commonly consume, for analysis in
Study 2.
There is no data to our knowledge describing the contribution of phosphorus and
potassium additives to the nutrient content of foods in Canada. This creates a challenge for both
patients with CKD and their clinicians to determine which foods are appropriate to consume
while on renal diet. In Study 2, we determined that MPF foods containing a phosphorus and/or
potassium additive on the ingredient list significantly contributes to the phosphorus and
potassium content of MPF foods. Potassium and phosphorus additives were generally found in
packaged, frozen or processed MPF foods, as opposed to fresh MPF foods. According to the
74
results of our questionnaire, less than half of participants looked for the word ‘phosphorus’ or
‘potassium’ on the ingredient list, which determines if the product contains additives. This is an
important finding as it indicates an area for improvement in patient education.
Phosphorus additives can increase the phosphorus content of foods by up to 59%. These
results were not entirely surprising as many studies that have taken place in the United States
(U.S.) and Europe demonstrated that the phosphorus content of foods with additives similarly
ranged from approximately 30 to 60% higher compared to foods that did not contain a
phosphorus additive (Léon et al, 2013; Cupisti et al, 2012; Benini et al, 2011; Sherman et al,
2009ab; Sullivan et al, 2007). In addition, regulations regarding the use of phosphorus additives
in meat and poultry foods in the U.S. are comparable to regulations in Canada as both countries
allow phosphorus additives in amounts up to 0.5% of the product formula by weight in meat and
poultry products (CFIA 2013, FSIS 2015). Phosphorus additives are considered to contribute to
the dietary phosphorus load as they are entirely bioavailable, unlike phosphorus naturally found
in foods which is only 40-60% absorbed in the gastrointestinal tract (Calvo et al, 2014).
Education regarding the avoidance of foods with phosphorus additives has been previously
shown to be an effective intervention for reducing serum phosphorus levels in the short term
(Sullivan et al, 2009). This in turn, may help moderate hyperphosphatemia and its complications,
however further studies are needed to demonstrate the effectiveness of dietary phosphorus
restriction on morbidity and mortality outcomes.
Meat and poultry products listing potassium lactate on the ingredient list contained up to
1100 mg of potassium in a 100g serving, which is more than half of the daily recommendation
for a patient with CKD requiring a potassium restriction (Sanghavi et al, 2013). These results
were in line with a previous study by Sherman & Mehta (2009b) where the authors noted the top
five enhanced products with the most potassium contained 692-930 mg potassium per 100
grams, which is considerably greater than the average potassium content of meat and poultry
products of the same weight (~300-375 mg K/100g). Potassium lactate is allowed up to 4% of
meat and poultry products in Canada (Health Canada, 2012b), which is equivalent to 1200 mg of
potassium in a 100g product and substantially greater than the maximum allowable amount of
phosphorus additives (0.5%) (CFIA, 2013). Therefore, potassium lactates may have the potential
to significantly contribute to the potassium content of meat and poultry products in Canada.
75
A previous study showed that MPF products injected with solutions by manufacturers
(labelled as ‘enhanced’ or ‘seasoned’) had significantly higher phosphorus to protein ratios than
foods that were not injected with solutions (Sherman & Mehta, 2009b). Therefore, it was a
surprising finding that poultry products labelled as ‘seasoned’ did not result in higher amounts of
phosphorus than products that were not labelled as ‘seasoned’. We attribute these results to the
fact that in Canadian regulations, the term ‘seasoned’ is not synonymous with the use
phosphorus additives. Therefore, we concluded that it is more effective for patients requiring a
dietary phosphorus restriction to look at the list of ingredients to determine if a product contains
an additive. If a product does not contain a list of ingredients, for example, fish from a seafood
counter, it is possible the product contains additives. In keeping with this finding, Ahuja et al
(2015) noted that sodium compounds may come in contact with fish and seafood products during
commercial processing.
We revealed in our study using a food questionnaire that approximately half of patients
reported choosing sodium reduced products most of the time. Importantly, study 3 determined
that sodium reduced meat and poultry products contain significantly more (44%) potassium that
their non-sodium reduced counterparts due to the use of potassium additives as a sodium
replacer, and are a significant source of potassium. Sodium reduced meat and poultry products
contain on average 38% less sodium and similar amounts of phosphorus and protein compared to
its original non sodium reduced counterpart. This was the first study to chemically analyze and
compare original and sodium reduced food product formulations.
As population-wide health strategies to reduce sodium levels in processed foods are being
implemented in various countries, such as Canada, United Kingdom and the U.S (Webster et al,
2014), sodium reduced food products will be increasingly available to consumers. In addition,
food additives containing phosphorus and potassium are continuously being approved for sodium
reduction and their use is likely underestimated. Manufacturers may be inclined to use potassium
additives due to its efficacy in lowering sodium and increasing potassium, which are both
associated with beneficial health outcomes. While the effects of potassium from fruits and
vegetables are known to be beneficial in the healthy population, the consequences of increased
potassium from potassium additives is not known and might be lead to unintentional negative
health effects in those with compromised kidney function.
76
The general population is likely unaware of the potential increase in potassium-based
additives in sodium reduced meat and poultry products. Furthermore, severe heart failure, kidney
disease and medications such as potassium-sparing diuretics, angiotensin converting enzyme
inhibitors and angiotensin receptor blockers can lead to impaired urinary potassium excretion.
With the increased prevalence of kidney disease, diabetes, heart failure and the use of multiple
anti-hypertensive agents, the risk of life-threatening hyperkalemia is likely to rise. Our results
support the inclusion of potassium content as a mandatory component on food labeling to
potentially decrease the risk of life-threatening hyperkalemia from potassium additives in
vulnerable populations.
7.1 Study Implications for Practice and Future Studies
Our findings directly impact nutrition education strategies and interventions for patients with
CKD in Canada. Patients should be educated to choose fresh, unpackaged versions of MPF
without additives most often as these foods have the least amount of sodium, phosphorus and
potassium. The exception to this guidance may be fresh seafood from a seafood counter, for
which an ingredient list is often not available and additives may be present. Therefore, the
availability of product information should be encouraged for products from the seafood counter.
Dietitians should be made aware that the term ‘seasoned’ is not synonymous with
phosphorus additives in poultry products. Seasoned products contain high amounts of sodium
and are not appropriate for those following a low sodium diet, such as those with CKD. For the
purpose of phosphorus restriction, it would be most effective to educate patients to identify and
avoid MPF products with phosphorus additives on the ingredient list. Since less than half of
patients surveyed reported looking for additives on the ingredient list, it would be beneficial to
increase efforts in educating patients to read the ingredient list to search for phosphorus
additives, and particularly potassium additives where there is a marked increase in potassium
content from potassium lactate.
Lastly, patients should be educated regarding the potential for increased potassium content in
sodium reduced meat and poultry products. Patients should be cautious when choosing sodium
77
reduced foods and look for potassium additives on the ingredient list, as well as the potassium
content on the nutrition facts table, if available.
Since there is wide variability in the phosphorus and potassium content of MPF foods
containing additives, it would be ideal for consumers to be able to access the nutrient content
information of these MPF products. Preferably, if food products containing additives had
phosphorus and potassium content present on the nutrition facts table, this may facilitate greater
adherence with dietary restrictions and allow for more food choices within the parameters of the
renal diet. Our findings can be used to advocate to policy makers for the requirement of
potassium and phosphorus content to be listed on the nutrition facts table of packaged food
products.
Further research is required to examine the discrepancies between the MPF subtypes
analyzed and the comparable CNF values (Appendix I). As the CNF should be a trusted source
of nutrient information, its accuracy is important to ensure patients are able to make appropriate
foods choices for their therapeutic dietary restrictions. While our study focused on MPF foods, it
would be interesting investigate other sources of protein and food groups known to contain
additives, such as commercially baked goods. In addition, as 21% of participants surveyed ate a
meal outside of the home at least 4-5 times per week, it would be important to analyze the
nutrient content commonly consumed fast-food items. Finally, as phosphorus and potassium
additives were less likely to be found in fresh MPF, future research is needed to examine
whether consuming a diet that consists of unprocessed, fresh foods leads to improved nutritional
markers and outcomes in CKD patients.
78
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APPENDICES
Appendix A – Food Questionnaire
94
Food Questionnaire
Study Title: The phosphorus and potassium content of frequently consumed
types of meat, poultry and fish items among patients with end-stage renal
disease
Participant ID # ___________
Date: ___________
ABOUT THIS SURVEY
We are asking you to complete this form to find out more about the
foods you have eaten at home, during the past month?
It will take approximately 25-35 minutes to complete. Please answer
each question as best you can and ask for help from the person who
shops and cooks most often in your home. Estimate if you aren’t
sure. Ask a research staff if you are unclear about a question.
1a) How often did you eat chicken that is NOT breaded (such as
breast, thighs, wings or drumsticks)?
□ NEVER (GO TO QUESTION 2)
□ 1 time in the past month □ 3-4 times per week
□ 2-3 times in the past month □ 5-6 times per week
□ 1 time per week □ 1 time per day
□ 2 times per week □ 2 or more times per day
1b) Each time you ate chicken, how much did you usually eat?
□ Less than 1 breast or thigh or less than 2 wings or drumsticks
□ 1 breast or thigh or 2 drumsticks or wings
□ More than 1 breast or thigh or more than 2 drumsticks or wings
95
1c) How do you usually buy chicken? (Check all that apply)
□ Fresh, packaged □ Fresh, from butcher or meat counter
□ Frozen, packaged □ Rotisserie, cooked
□ I don’t know □ Other (please
explain):_____________________
1d) If you buy a specific brand of chicken most often, please state this
brand: ____________________________________________
2a) How often did you eat breaded chicken (including nuggets,
breaded wings, breaded burgers and chicken fingers)?
□ NEVER (GO TO QUESTION 3)
□ 1 time in the past month □ 3-4 times per week
□ 2-3 times in the past month □ 5-6 times per week
□ 1 time per week □ 1 time per day
□ 2 times per week □ 2 or more times per day
2b) Each time you ate breaded chicken, how much did you usually
eat?
□ Less than 1 patty or less than 4 nuggets or less than 2 wings
□ 1 patty or 4-8 nuggets or 2 wings
□ More than 1 patty or more than 8 nuggets or more than 2 wings
2c) How do you usually buy your breaded chicken?
□ Frozen / Packaged
□ I buy fresh chicken that I coat in breadcrumbs myself
□ I don’t know □ Other (please
explain):_____________________
96
2d) If you buy a specific brand of breaded chicken most often, please
state this brand:
3a) How often did you eat turkey (such as roast turkey or turkey
cutlets)?
□ NEVER (GO TO QUESTION 4)
□ 1 time in the past month □ 3-4 times per week
□ 2-3 times in the past month □ 5-6 times per week
□ 1 time per week □ 1 time per day
□ 2 times per week □ 2 or more times per day
3b) Each time you ate turkey, how much did you usually eat?
Note: 3 oz is about the size of a deck of cards
□ Less than 2 ounces
□ 2 to 5 ounces
□ More than 5 ounces
3c) How do you usually buy turkey?
□ Fresh, packaged □ Fresh, from butcher or meat counter
□ Frozen, packaged □ I don’t know
□ Other (please explain):_____________________
3d) If you buy a specific brand of turkey most often, please state this
brand:
97
4a) How often did you eat turkey cold cuts or chicken cold cuts (such
as luncheon meat, turkey ham, turkey salami or turkey pastrami?)
□ NEVER (GO TO QUESTION 5)
□ 1 time in the past month □ 3-4 times per week
□ 2-3 times in the past month □ 5-6 times per week
□ 1 time per week □ 1 time per day
□ 2 times per week □ 2 or more times per day
4b) Each time you ate turkey or chicken cold cuts, how much did you
usually eat?
□ Less than 1 slice
□ 1 to 3 slices
□ More than 3 slices
4c) How do you usually buy your turkey or chicken cold cuts?
□ Pre-packaged □ From the deli counter □ I don’t
know
□ Other (please explain):_____________________
4d) If you buy a specific brand of turkey or chicken cold cuts most
often, please state this brand:
98
5a) How often did you eat luncheon ham or deli-style ham
□ NEVER (GO TO QUESTION 6)
□ 1 time in the past month □ 3-4 times per week
□ 2-3 times in the past month □ 5-6 times per week
□ 1 time per week □ 1 time per day
□ 2 times per week □ 2 or more times per day
5b)Each time you ate luncheon ham or deli-style ham, how much did
you usually eat?
□ Less than 1 slice
□ 1 to 3 slices
□ More than 3 slices
5c) How do you usually buy your luncheon ham or deli-style ham?
□ Pre-packaged □ From the deli counter □ I don’t
know
□ Other (please explain):_____________________
5d) If you buy a specific brand of luncheon ham or deli-style ham
most often, please state this brand:
99
6a) How often did you eat other cold cuts or luncheon meats (such as
bologna, salami, corned beef, pastrami and others)?
□ NEVER (GO TO QUESTION 7)
□ 1 time in the past month □ 3-4 times per week
□ 2-3 times in the past month □ 5-6 times per week
□ 1 time per week □ 1 time per day
□ 2 times per week □ 2 or more times per day
6b)Each time you ate other cold cuts or luncheon meats, how much
did you usually eat?
□ Less than 1 slice
□ 1 to 3 slices
□ More than 3 slices
6c) How do you usually buy your cold cuts or luncheon meats?
□ Pre-packaged □ From the deli counter □ I don’t
know
□ Other (please explain):_____________________
6d) If you buy a specific brand of cold cuts or luncheon meats most
often, please state this brand:
100
7a) How often did you eat beef hamburgers that were NOT from a fast
food or other restaurant?
□ NEVER (GO TO QUESTION 8)
□ 1 time in the past month □ 3-4 times per week
□ 2-3 times in the past month □ 5-6 times per week
□ 1 time per week □ 1 time per day
□ 2 times per week □ 2 or more times per day
7b) Each time you ate beef hamburgers, how much did you usually
eat?
□ Less than 1 patty or less than 2 ounces
□ 1 patty or 2 to 4 ounces
□ More than 1 patty or more than 4 ounces
7c) How do you usually buy your beef hamburgers?
□ Frozen / Packaged □ Homemade hamburgers from fresh ground
beef
□ I don’t know □ Other (please
explain):_____________________
7d) If you buy a specific brand of beef hamburgers most often, please
state this brand:
101
8a) How often did you eat roast beef, pot roast, steak or other forms
of beef? (We will ask about ground beef and steak later on)
□ NEVER (GO TO QUESTION 9)
□ 1 time in the past month □ 3-4 times per week
□ 2-3 times in the past month □ 5-6 times per week
□ 1 time per week □ 1 time per day
□ 2 times per week □ 2 or more times per day
8b) Each time you ate beef, how much did you usually eat?
Note: 3 oz is about the size of a deck of cards
□ Less than 2 ounces
□ 2 to 6 ounces
□ More 6 ounces
8c) How do you usually buy your beef?
□ Fresh, packaged □ Fresh, from butcher or meat counter
□ Frozen, packaged □ I don’t know
□ Other (please explain):_____________________
8d) If you buy a specific brand of beef most often, please state this
brand:
102
9a) How often did you eat steak (beef)?
□ NEVER (GO TO QUESTION 10)
□ 1 time in the past month □ 3-4 times per week
□ 2-3 times in the past month □ 5-6 times per week
□ 1 time per week □ 1 time per day
□ 2 times per week □ 2 or more times per day
9b) Each time you ate steak, how much did you usually eat?
Note: 3 ounces is about the size of a deck of cards
□ Less than 3 ounces
□ 3 to 7 ounces
□ More than ounces
9c) How do you usually buy steak?
□ Fresh, packaged □ Fresh, from butcher or meat counter
□ Frozen, packaged □ I don’t know
□ Other (please explain):_____________________
9d) If you buy a specific brand of steak most often, please state this
brand:
103
10a) How often did you eat ground beef in mixtures (such as
meatballs, casseroles, chili or meatloaf)?
□ NEVER (GO TO QUESTION 11)
□ 1 time in the past month □ 3-4 times per week
□ 2-3 times in the past month □ 5-6 times per week
□ 1 time per week □ 1 time per day
□ 2 times per week □ 2 or more times per day
10b) Each time you ate ground beef in mixtures, how much did you
usually eat?
□ Less than 3 ounces or less than ½ cup
□ 3 to 8 ounces or ½ cup to 1 cup
□ More than 8 ounces or more than 1 cup
10c) How do you usually buy ground beef in mixtures?
□ Frozen, packaged □ Fresh ground beef used in homemade
mixture
□ I don’t know □ Other (please
explain):_____________________
10d) If you buy a specific brand of ground beef in mixtures most
often, please state this brand:
104
11a) How often did you eat pork spareribs or beef spareribs?
□ NEVER (GO TO QUESTION 12)
□ 1 time in the past month □ 3-4 times per week
□ 2-3 times in the past month □ 5-6 times per week
□ 1 time per week □ 1 time per day
□ 2 times per week □ 2 or more times per day
11b) Each time you ate spareribs, how much did you usually eat?
□ Less than 4 ribs
□ 4 to 12 ribs
□ More than 12 ribs
11c) How do you usually buy your spareribs?
□ Fresh, packaged □ Fresh, from meat counter
□ Frozen, packaged □ I don’t know
□ Other (please explain):_____________________
11d) If you buy a specific brand of spareribs most often, please state
this brand:
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12a) How often did you eat pork (including chops, roasts, and in
mixed dishes)?
□ NEVER (GO TO QUESTION 13)
□ 1 time in the past month □ 3-4 times per week
□ 2-3 times in the past month □ 5-6 times per week
□ 1 time per week □ 1 time per day
□ 2 times per week □ 2 or more times per day
12b) Each time you ate pork, how much did you usually eat?
Note: 3 ounces is about the size of a deck of cards
□ Less than 1 ounce
□ 1 to 3 ounces
□ More 3 ounces
12c) How do you usually buy your pork?
□ Fresh, packaged □ Fresh, from meat counter
□ Frozen, packaged □ I don’t know
□ Other (please explain):_____________________
12d) If you buy a specific brand of pork most often, please state this
brand:
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13a) How often did you eat baked ham or ham steak?
□ NEVER (GO TO QUESTION 14)
□ 1 time in the past month □ 3-4 times per week
□ 2-3 times in the past month □ 5-6 times per week
□ 1 time per week □ 1 time per day
□ 2 times per week □ 2 or more times per day
13b) Each time you ate baked ham or ham steak, how much did you
usually eat? Note: 3 ounces is about the size of a deck of cards
□ Less than 1 ounce
□ 1 to 3 ounces
□ More 3 ounces
13c) How do you usually buy your baked ham or ham steak?
□ Packaged, cooked □ Meat counter, cooked □ Canned
□ I don’t know □ Other (please
explain):_____________________
13d) If you buy a specific brand of baked ham or ham steak most
often, please state this brand:
14a) How often did you eat bacon?
□ NEVER (GO TO QUESTION 15)
□ 1 time in the past month □ 3-4 times per week
□ 2-3 times in the past month □ 5-6 times per week
□ 1 time per week □ 1 time per day
□ 2 times per week □ 2 or more times per day
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14b) Each time you ate bacon, how much did you usually eat?
□ Fewer than 2 slices
□ 2 to 4 slices
□ More than 4 slices
14c) How do you usually buy your bacon?
□ Fresh, packaged □ Fresh, from meat counter
□ I don’t know
□ Other (please explain):___________________
14d) If you buy a specific brand of bacon most often, please state this
brand:
15a) How often did you eat sausage? (Please do not include hot dogs,
wieners or frankfurters)
□ NEVER (GO TO QUESTION 16)
□ 1 time in the past month □ 3-4 times per week
□ 2-3 times in the past month □ 5-6 times per week
□ 1 time per week □ 1 time per day
□ 2 times per week □ 2 or more times per day
15b) Each time you ate sausage, how much did you usually eat?
□ Less than 2 small links or less than 1 large link
□ 2 to 5 small links or 1 to 2 large links
□ More than 5 small links or more than 2 large links
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15c) How do you usually buy sausage?
□ Fresh, packaged □ Fresh, from deli counter □ I don’t
know
□ Frozen, packaged □ Other (please
explain):_____________________
15d) If you buy a specific brand of sausage most often, please state
this brand:
__________________________________________________________
16a) How often did you eat hot dogs, wieners or frankfurters?
□ NEVER (GO TO QUESTION 17)
□ 1 time in the past month □ 3-4 times per week
□ 2-3 times in the past month □ 5-6 times per week
□ 1 time per week □ 1 time per day
□ 2 times per week □ 2 or more times per day
16b)Each time you ate hot dogs, wieners or frankfurters, how much
did you usually eat?
□ Less than 1 hot dog
□ 1 to 2 hot dogs
□ More than 2 hot dogs
16c) How do you usually buy hot dogs, wieners or frankfurters?
□ Fresh, packaged □ Fresh, from deli counter
□ Frozen, packaged □ I don’t know
□ Other (please explain):_____________________
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16d) If you buy a specific brand hot dogs, wieners and frankfurters
most often, please state this brand:
17a) How often did you eat canned tuna (including in salads,
sandwiches or casseroles)?
□ NEVER (GO TO QUESTION 18)
□ 1 time in the past month □ 3-4 times per week
□ 2-3 times in the past month □ 5-6 times per week
□ 1 time per week □ 1 time per day
□ 2 times per week □ 2 or more times per day
17b) Each time you ate canned tuna, how much did you usually eat?
□ Less than ¼ cup or less than 2 ounces
□ ¼ to ½ cup or 2 to 3 ounces
□ More than ½ cup or more than 3 ounces
17c) If you buy a specific brand of canned tuna most often, please
state this brand:
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18a) How often did you eat canned salmon (including in salads,
sandwiches or casseroles)?
□ NEVER (GO TO QUESTION 19)
□ 1 time in the past month □ 3-4 times per week
□ 2-3 times in the past month □ 5-6 times per week
□ 1 time per week □ 1 time per day
□ 2 times per week □ 2 or more times per day
18b) Each time you ate canned salmon, how much did you usually eat
□ Less than ¼ cup or less than 2 ounces
□ ¼ to ½ cup or 2 to 3 ounces
□ More than ½ cup or more than 3 ounces
18c) If you buy a specific brand of canned salmon most often, please
state this brand:
19a) How often did you eat dark or oily fish like salmon, fresh tuna,
trout, or mackerel that is NOT breaded, canned or smoked?
□ NEVER (GO TO QUESTION 20)
□ 1 time in the past month □ 3-4 times per week
□ 2-3 times in the past month □ 5-6 times per week
□ 1 time per week □ 1 time per day
□ 2 times per week □ 2 or more times per day
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19b) Each time you ate dark or oily fish, how much did you usually
eat?
□ Less than 2 ounces or less than 1 fillet
□ 2 to 6 ounces or 1 fillet
□ More than 6 ounces or more than 1 fillet
19c) How do you usually buy dark or oily fish?
□ Fresh, packaged □ From seafood counter
□ Frozen, packaged □ I don’t know
□ Other (please explain):_____________________
19d) If you buy a specific brand of dark or oily fish most often, please
state this brand:
___________________________________________________________
20a) How often did you eat white or lean fish like cod, haddock, perch
or sole that is NOT breaded, canned or smoked?
□ NEVER (GO TO QUESTION 21)
□ 1 time in the past month □ 3-4 times per week
□ 2-3 times in the past month □ 5-6 times per week
□ 1 time per week □ 1 time per day
□ 2 times per week □ 2 or more times per day
20b) Each time you ate white or lean fish, how much did you usually
eat?
□ Less than 2 ounces or less than 1 fillet
□ 2 to 6 ounces or 1 fillet
□ More than 6 ounces or more than 1 fillet
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20c) How do you usually buy white or lean fish?
□ Fresh, packaged □ From seafood counter
□ Frozen, packaged □ I don’t know
□ Other (please explain):_____________________
20d) If you buy a specific brand of white or lean fish most often,
please state this brand:
____________________________________________________________
21a) How often did you eat shrimp?
□ NEVER (GO TO QUESTION 22)
□ 1 time in the past month □ 3-4 times per week
□ 2-3 times in the past month □ 5-6 times per week
□ 1 time per week □ 1 time per day
□ 2 times per week □ 2 or more times per day
21b) Each time you ate shrimp, how much did you usually eat?
Note: 1 ounce is about 4 medium-sized shrimp
□ Less than 1 ounce
□ 1 to 4 ounces
□ More than 4 ounces
21c) How do you usually buy shrimp?
□ From seafood counter □ Frozen, packaged, not breaded
□ Frozen, packaged, breaded □ I don’t know
□ Other (please explain):_____________________
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21d) If you buy a specific brand of shrimp most often, please state
this brand:
22a) How often did you eat other shellfish (such as crab, lobster or
scallops)?
□ NEVER (GO TO QUESTION 23)
□ 1 time in the past month □ 3-4 times per week
□ 2-3 times in the past month □ 5-6 times per week
□ 1 time per week □ 1 time per day
□ 2 times per week □ 2 or more times per day
22b) Each time you ate shellfish, how much did you usually eat?
□ Less than 1 ounce
□ 1 to 4 ounces
□ More than 4 ounces
22c) How do you usually buy shellfish?
□ From seafood counter □ Frozen, packaged
□ I don’t know
□ Other (please explain):_____________________
22d) If you buy a specific brand of shellfish most often, please state
this brand:
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23a) How often did you eat battered/breaded fish or fish sticks?
□ NEVER (GO TO QUESTION 24)
□ 1 time in the past month □ 3-4 times per week
□ 2-3 times in the past month □ 5-6 times per week
□ 1 time per week □ 1 time per day
□ 2 times per week □ 2 or more times per day
23b) Each time you ate battered/breaded fish or fish sticks, how much
did you usually eat?
□ Less than 2 ounces or less than 1 fillet
□ 2 to 6 ounces or 1 fillet
□ More than 6 ounces or more than 1 fillet
23c) How do you usually buy battered/breaded fish or fish sticks?
□ Frozen, packaged □ Fresh fish that I bread or batter myself
□ I don’t know
□ Other (please explain):_____________________
23d) If you buy a specific brand of battered/breaded fish or fish sticks
most often, please state this brand:
____________________________________________________________
24) Is there any other type of meat, poultry or fish product that you
ate, that was not included in the previous questions?
____________________________________________________________
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25) At which grocery store(s) do you shop? (Check all that apply)
□ Sobey’s □ Metro
□ Loblaws □ Costco
□ No Frills □ Great Canadian Superstore
□ Other _____________________________
26) Who usually does the grocery shopping at home?
□ You □ Spouse / Partner □ Children □ Caregiver / Parent
□ Other _______________________
27) Who usually does the cooking at home?
□ You □ Spouse / Partner □ Children □ Caregiver / Parent
□ Other _______________________
28) During the past month, how often did you eat a meal outside of
the home (includes restaurants, fast food, coffee shops)?
□ More than once a day □ Once a day □ 4-5 times per week
□ 2-3 times per week □ 1-2 times per week □ 2-3 times per month
□ Once per month □ Less than once per month
29) If you are asked to follow a low phosphorus diet, do you think you
are following it?
□ I am not asked to follow a low phosphorus diet
□ I try to follow a low phosphorus diet and I usually do
□ I try to follow a low phosphorus diet, but I don’t always follow it
□ I don’t follow a low phosphorus diet
□ I don’t know what a low phosphorus diet is
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30) If you are asked to follow a low potassium diet, do you think you
are following it?
□ I am not asked to follow a low potassium diet
□ I try to follow a low potassium diet and I usually do
□ I try to follow a low potassium diet, but I don’t always follow it
□ I don’t follow a low potassium diet
□ I don’t know what a low potassium diet is
31) If you read the Nutrition Facts table (see picture) to
find out about the nutritional content of the food, what
do you usually look for? (check all that apply)
□ Calories □ Sodium □ Fat
□ Protein □ Phosphorus □ Potassium
□ Carbohydrate □ Sugar □ Fiber
□ I don’t read the nutrition facts table □ I don’t
know
32) Do you use the salt substitute called NoSalt©, NuSalt© or HalfSalt©,
when you cook?
□ I often use a salt substitute □ I sometimes use a salt substitute
□ I never use a salt substitute □ I don’t know
33) If you read the list of ingredients of the food you buy, what do you
usually look for? (check all that apply)
□ I don’t read the ingredient list
□ Ingredients with the word “phosphorus” or letters “phos”
□ Ingredients with the word “potassium”
□ Other ingredient (please specify): ______________________________
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34) How often do you try to choose foods that say “Sodium-Free” or
“No Sodium” or “No Added Salt” on the food package?
□ Most of the time □ Some of the time □ Never □ I don’t know
35) How often do you try to choose foods that say “Reduced in
Sodium” or “25% Less Sodium” or “Lightly Salted” or “Lower in
Sodium” on the package?
□ Most of the time □ Some of the time □ Never □ I don’t know
Demographic Information
Reminder: All information given here and throughout the
questionnaire, will be kept confidential
36) Where do you live?
□ House □ Apartment □ Nursing Home □ Other: __________
37) How many people do you live with?
□ No one else □ 1 □ 2 □ 3 □ 4 or more
38) What is your highest level of education obtained?
□ Elementary School □ Some high school
□ High school diploma □ Some university / college
education
□ University / college degree □ Graduate education
□ None
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39) Please identify your ethnic origin? (Sample geographic
backgrounds in brackets). Check all that apply:
□ Aboriginal (Inuit, First Nations, Metis, Aborigine, Maori)
□ African / Black (Afro-Caribbean, Kenyan, Ethiopian, Moroccan, Nigerian,
Egyptian)
□ Australasian / Pacific Islander (Australia, New Zealander, Fijian,)
□ Caribbean (Jamaican, Antiguan, Trinidadian)
□ Central Asian (Uzbeck, Afghan)
□ East Asian (Chinese, Japanese, Korean)
□ Caucasian / White / European (British, French, Greek, Italian, Russian)
□ Latin American (Brazilian, Peruvian, Nicaraguan, Mexican, Argentinean)
□ Middle Eastern / West Asian (Israeli, Palestinian, Armenian, Iraqi,
Iranian)
□ South Asian (Indian, Indo-Caribbean, Pakistani, Sri Lankan)
□ South-East Asian (Filipino, Laotian, Vietnamese)
□ Unknown
□ Other, please specify _________________________________________
40) What is your household annual income before taxes from all
sources?
□ Greater than $100,000
□ $80,000 – less than $100,000
□ $60,000 – less than $80,000
□ $40,000 – less than $ 60,000
□ $20,000 – less than $40,000
□ Less than $20,000
□ No income
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Appendix B – Face Validation Recruitment Pre-Amble
Food Questionnaire
120
Study Title: The phosphorus and potassium content of frequently consumed types of meat, poultry and fish items
among patients with end-stage renal disease
Face Validation Recruitment Pre-Amble
RGM = Research Group Member RGM: I would like your help in making a questionnaire for a dialysis nutrition
study. The questionnaire is about which types of meat, poultry and fish products you eat at home most often. It will also include questions about how you or your primary caregiver purchase and prepare foods and some general questions about you. This information will help us learn more about what you eat, so we can study these foods in more detail.
Would you like to hear more about how you can help us with the
questionnaire?
Patient: Yes or No RGM: IF NO: Not a problem. Thank you for your time.
IF YES: You will be asked to carefully read each question in the diet questionnaire. As you answer the questions, we will want you to comment on if they are easy to understand and to let us know about words that are not clear. We will also want to know whether you feel the questions are appropriate, and whether you would choose not to answer certain ones. You can write your comments directly on the questionnaire. You will not be required to answer all of the questions on the questionnaire if you do not wish to. It will take approximately 25-35 minutes to go through the questionnaire. The information you give will be kept confidential and your answers will not be used in the study. Do you have any questions or concerns?
Patient: (Answer any questions the patient has to the best of your ability. If needed, the principal investigator can be contacted to answer any questions of uncertainty)
RGM: Are you interested in providing your feedback about this questionnaire
Mr/Mrs. _____?
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Patient: Yes or No RGM: IF NO: Not a problem. Thank you for your time and consideration.
IF YES: Thank you for your help. Your comments will give us important information and will be very helpful in this research project.
RGM: (Provide patient and/or primary household shopper / caregiver with a copy of the questionnaire, and explain how to comment)
In case the pt asks why we need their help: We need your feedback to help us make a clear and concise questionnaire about the foods that dialysis patients eat at home. We will use all of the feedback to improve the questionnaire and make sure that it is asking the right questions in a way that is understandable by everyone. Then we would like to use it for a study that we are planning to do. The reason we are planning to do this study is because meat, poultry and fish food items are important sources of protein in the hemodialysis diet and may contain added amounts of potassium and/or phosphorus that are not seen on the nutritional label. The results of the questionnaire will help us determine the meat, poultry and fish products that patients consume most often. We will use this information to help us decide which foods to analyze for the phosphorus, potassium and sodium content. There is currently no Canadian information about the amount of phosphorus and potassium in foods that contain additives, so the study that we are planning to do will give us more information to help patients with kidney disease to better manage their renal diet.
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Appendix C – Recruitment Pre-Amble
Food Questionnaire
123
Study Title: The phosphorus and potassium content of frequently consumed types of meat, poultry and fish items
among patients with end-stage renal disease
Recruitment Pre-Amble
RGM = Research Group Member RGM: I would like to talk to you about an opportunity to take part in a dialysis
nutrition study. The study is about which types of meat, poultry and fish products you consume most often. In order to do this, we will give you a questionnaire to complete, which will include questions about which types of meat, fish and poultry you purchase and how frequently you eat them.
The reason we are doing this study is because meat, poultry and fish food items are important sources of protein for your diet and may contain added amounts of potassium and/or phosphorus that are not seen on the nutritional label. We will use the information you provide us to find out more about the phosphorus, potassium and sodium content of meat, poultry and fish products that you consume most often. There is currently no Canadian information about the amount of phosphorus and potassium contained in foods with additives, so this study will help give us more information to help manage the renal diet. Would you like to hear more about the study?
Patient: Yes or No RGM: IF NO: No problem. Thank you for your time.
IF YES: To participate in the study, you will be asked to fill out a questionnaire which has questions about which types of meat, fish and poultry you purchase and how often you eat them. It will also include questions about how you or the primary caregiver purchase and prepare foods and some general questions about you. The research staff will also collect some information from your chart about your kidney disease. The questionnaire should take approximately 25-35 minutes to complete. You can decide to complete it right away, or to take it home and bring it back at a later visit. You may choose not to answer or skip any questions. However, if you require clarification in order to answer a question, we will be available to assist you.
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There are no risks anticipated with this study. Also, your participation is completely voluntary. You also have the right to withdraw from this study at any time and your medical care will not be affected. Do you have any questions or concerns?
Patient: (Answer any questions the patient has to the best of your ability. If needed, the principal investigator can be contacted to answer any questions of uncertainty)
RGM: Are you interested in participating in this study Mr/Mrs. _____? Patient: Yes or No RGM: IF NO: No problem. Thank you for your time.
IF YES: Please read the consent form. If you cannot read the consent form, let me know, and I will read it to you. You may take as much time as you like to decide if you wish to participate in the study. Please also let me know if you have any questions about the study. If you decide to participate, you will be asked to sign and date the consent form. You will then be given a copy of the consent form for your reference.
Patient: (May potentially ask questions) (Signs the consent form OR Doesn’t Sign the Consent form) RGM: IF NO: No problem. Thank you for your time.
IF YES: Thank you for deciding to participate. Your participation will give us valuable information and will be very helpful in this research project. (Photocopy the consent form. Give the copy to the participant and store the original in the white binder labeled “Study 1 research consent forms”)
RGM: (Provide patient and/or primary household shopper / caregiver with a copy
of the questionnaire, and explain how to complete the questionnaire. Provide assistance in completed the questionnaire as needed.)
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Appendix D – Patient Consent Form
Food Questionnaire
126
Consent to Participate in a Research Study
Study Title: The phosphorus and potassium content of frequently consumed types of meat, poultry and fish items among patients with end-stage renal disease
Study Investigators and Study Contact: Principal Investigator:
Arti Sharma Parpia, RD St. Michael’s Hospital 30 Bond Street, 8CC, Rm 014 Toronto, ON M5B 1W8 Tel: (416) 864-6060 ext. 6113 Availability: 9:00 am – 5:00 pm, Monday to Friday
Co-Investigators:
Pauline Darling, RD, PhD 1. Associate Scientist, Li Ka Shing Knowledge Institute St. Michael’s Hospital 2. 209 Victoria Street, 4th Floor, Suite 411 3. Toronto, ON M5B 1W8 4. Tel: (416) 978-5556 Availability: 9:00 am – 5:00 pm, Monday to Friday
Marc Goldstein, MD
Staff Nephrologist, St Michael’s Hospital 30 Bond Street, 8CC, Rm 014 Toronto, ON M5B 1W8 Tel: (416) 864-5290 Availability: 9:00 am – 5:00 pm, Monday to Friday
Mary L’Abbé, PhD
Earle W. McHenry Professor, and Chair, Department of Nutritional Sciences Faculty of Medicine, University of Toronto FitzGerald Building, 150 College Street, Rm 315 Toronto, ON, Canada M5S 3E2 Tel: (416) 978-7235 Availability: 9:00 am – 5:00 pm, Monday to Friday
Other Research Study Members:
Carol Huang, RD Registered Dietitian, Nephrology St. Michael’s Hospital
Kristen Wetherall, HBSc Dietetic Student, Volunteer Services St. Michael’s Hospital
Maxine Seider, BSc, MSc Volunteer Research Assistant St. Michael’s Hospital
Ms Arti Sharma Parpia is a student at the University of Toronto, working on a Masters of Science degree in the Department of Nutritional Sciences. Ms Sharma Parpia’s faculty supervisor is Dr. Pauline Darling.
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Introduction You are asked to consider participating in our study to find out more about the food you usually eat at home. Before agreeing to take part in this research study, it is important that you read all of the information in this research consent form. If you cannot read, this information will be read to you. This form includes details we think you need to know in order to decide if you wish to take part in the study. All research is voluntary and you do have the option to decline participation in this research study. If you have any questions, ask a study investigator or a research study member. You should not sign this form until you are sure you understand the information. Purpose of the Research Study You are asked to consider participating in this study to find out more about the types of meat, poultry and fish products you usually eat at home. Meat, poultry and fish food items are important sources of protein for your diet and may contain added amounts of potassium and/or phosphorus that are not seen on the nutritional label. We will use the information you provide us to find out more about the phosphorus, potassium, protein and sodium content of the foods most commonly eaten by patients with chronic kidney disease. Description of the Research Study If you choose to participate in this study, you will be asked to complete a questionnaire which will include questions about which types of meat, fish and poultry you usually eat at home and how frequently you eat them. It will also include questions about how you or the food shopper at your home, purchases and prepares the food at your home, and some general questions about your education, ethnicity and annual income. The questionnaire should take approximately 25-35 minutes to complete. You can decide to complete it right away, or to take it home and bring it back at a later visit. We will also collect demographic information (e.g., age, gender) and information about your kidney disease and nutritional status from your medical record. There will be about 100 individuals participating in this study being conducted at St. Michael’s Hospital. Potential Harms There are no harms anticipated with participation in this study. Completing the questionnaire may be a slight inconvenience. If you feel uncomfortable answering any of the questions, you can choose not to answer them. Potential Benefits You may receive no direct benefits from being in this study. However, results from this study will be used to provide further information about the protein, potassium, phosphorus, and sodium content of foods with and without additives, which may help in managing chronic kidney disease. Protecting Your Health Information All information obtained during this study will remain confidential. You will be identified by a study code number and any personal information that includes your name will be securely stored in a locked cabinet, inside a locked room. Only your study code number will be on the data collection forms. The data collection forms will also be securely stored in a locked cabinet in a locked room. Electronic files will be stored securely on the hospital/institutional network. No information identifying you will be allowed off site in any form. The investigators will protect your records and keep all the information in your study file confidential to the greatest extent possible. However, it is important to understand that despite
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these protections being in place, there is a risk of unintentional release of information. Experience in similar studies indicates that the greatest risk in this study to you is the unintentional release of information from your health records. The chance that this information will accidentally be given to someone else is small. By signing this form, you are authorizing access to your medical records by the study investigators/study team, and the St. Michael’s Hospital Research Ethics Board. Such access will be used only for the purpose of verifying the authenticity and accuracy of the information collected for the study, without violating your confidentiality to the extent permitted by applicable laws and regulations. Federal and Provincial Data Protection regulations, including the Personal Information Protection and Electronic Documents Act (PIPEDA 2000) and the Personal Health Information Protection Act (PHIPA 2004) of Ontario, protect your personal information. They also give you the right to control the use of your personal information (including personal health information) and require your written permission for this personal information to be collected, used, or disclosed for the purposes of this study, as described in this consent form. You have the right to review and copy your personal information collected in this study, and to request corrections to any information inaccurately recorded. Once the study has been completed and published, the link between your name/ identifying information and your study data will be broken. The study data will be kept in a secure location for up to 10 years and then securely destroyed. In no way does signing this form waive your legal rights nor release the investigators or involved institutions from their legal and professional responsibilities. Study Results The study results may be presented as a Masters thesis at the University of Toronto. It is possible that the results of this study may be published in scientific literature or presented at a conference or seminar. Confidentiality will be upheld and no names or identifying information about you will be used in any publication or presentation. If you are interested in obtaining a copy of the study results/publication, please contact Arti Sharma Parpia, Principal Investigator. Participation and Withdrawal Participation in any research study is voluntary. If you choose not to participate, you and your family will continue to have access to customary care at St. Michael’s Hospital. If you decide to participate in this study you can change your mind without giving a reason, and you may withdraw from the study at any time without any effect on the care you and your family will receive at St. Michael’s Hospital.
If you withdraw from the study, your study data/information collected about you up to that time will be used to maintain the integrity of the study, but no more data about you will be collected. Research Ethics Board Contact If you have any questions regarding your rights as a research participant, you may contact Dr. Bob Hyland, Chair of Research Ethics Board, St. Michael’s Hospital, at 416-864-6060 ext. 2557 during business hours. The Research Ethics Board is also required to do periodic review of ongoing research studies. As part of this review, someone may contact you from the Research Ethics Board to discuss your experience in the research study. Study Contact If you have any further questions about this study, please call Arti Sharma Parpia, Principal Investigator at St. Michael’s Hospital, Hemodialysis Unit at (416) 864-6060 ext. 6113.
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Appendix E – Data Collection Form
Food Questionnaire
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Data Collection Form
(Data from chart)
Participant ID # _______________
Date: _______________
1) Age (years): _________
2) Gender: □ Male □ Female
3) Dialysis Vintage / Dialysis Start Date: ________________
4) Mode of Dialysis: □ Conventional In-centre hemodialysis (4 hours, 3x/week) □ Home Peritoneal Dialysis □ Short Daily In-Centre Dialysis □ Other: ________________________________________
5) Significant Co-Morbidities
□ Diabetes □ Hypertension □ Cardiovascular Disease
6) Dry Weight: ___________
7) Height: ___________
8) BMI: ___________
9) Biochemical Indices of Nutritional Status:
Albumin: __________ PO4: ___________ Calcium :___________ Potassium: __________ Pre-Dialysis Urea ________ PRU: _____________
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Appendix F
Comparison of Store Brands and National Brands among Major
Subgroups of MPF Foods
132
Comparison of store brands and national brands among major subgroups of MPF foods
Chicken Beef Fish and Seafood Processed Meats
Store Brand
n =12
National
Brand
n = 11
Store Brand
n = 11
National
Brand
n = 1
Store Brand
n = 14
National
Brand
n = 6
Store Brand
n = 7
National
Brand
n = 10
Mean (SD)
(min, max)
Mean (SD)
(min, max)
Mean (SD)
(min, max)
Mean (SD)
(min, max)
Mean (SD)
(min, max)
Mean (SD)
(min, max)
Mean (SD)
(min, max)
Mean (SD)
(min, max)
Sodium
(mg/100g) 282 (149)
(49, 470)
404 (214)
(51, 690)
247 (213)
(60, 540) 440
322 (215)
(42, 700)
251 (209)
(34, 590)
1590 (708)
(950,2800)
1083 (275)
(800,1800)
Potassium
(mg/100g) 449 (191)
(300, 920)
465 (219)
(310,1100)
360 (80)
(250, 480) 300
175 (147)
(22, 420)
233 (164)
(10, 450)
350 (128)
(220, 570)
574 (328)
(230,1100)
Phosphorus
(mg/100g) 218 (30)
(190, 290)
257 (53)
(190, 360)
214 (39)
(150, 270) 170
236 (91)
(130, 510)
213 (51)
(140, 290)
290 (121)
(150, 500)
274 (45)
(200, 370)
Protein
(g/100g) 26 (2)
(23, 29)
26 (3)
(22, 30)
23 (6)
(13, 33) 16
17 (2)
(13, 21)
18 (4)
(12, 23)
26 (13)
(13, 49)
20 (9)
(13, 41)
Phosphorus:Protein
(mg P/g Pro) 8.3 (1.0)
(7.3, 10.2)
10.2 (2.5)
(7.4, 15.8)
9.6 (1.2)
(8.1, 12.1) 10.2
14.1 (5.3)
(9.1, 27.9)
12.0 (3.2)
(9.2, 17.4)
11.9 (4.1)
(8.6, 19.9)
15.1 (4.7)
(9.1, 19.8)
PO4 additives
(n, %) 0 (0) 4 (36) 1 (9) 0 (0) 4 (29) 3 (50) 7 (100) 7 (70)
Seasoned
(n, %) 9 (75) 6 (55) 1 (9) 0 (0) 0 (0) 0 (0) 1 (14) 2 (20)
Price
Mean (SD) 12.06
(5.20)
10.66
(3.83) 8.57 (2.89) 14.99 7.60 (3.74) 7.66 (1.97) 5.21 (1.14) 5.12 (1.06)
Comments: We were unable to ascertain if store brands differed from national brands due to variability in
products. There were no consistent trends observed and it was challenging to further analyze subgroups
due to small sample sizes. In addition, some types of MPF were all store brand (i.e. rotisserie chicken,
ground beef, steak), therefore we were unable to make a comparison.
133
Appendix G
Comparison of Analyzed Nutrient Content Among
Processed and Minimally Processed Foods
134
Comparison of analyzed nutrient content among processed and minimally processed foods
(n=91)
Processed
n=55
Minimally
Processed* n=36
Mann-Whitney
Median (min, max) Median (min, max) p-value
Sodium
(mg/100g) 510 (200, 2800) 62 (34, 460) < 0.001
Potassium
(mg/100g) 320 (<10, 1100) 400 (66, 490) 0.12
Phosphorus
(mg/100g) 230 (130, 500) 235 (100, 510) 0.75
Protein
(g/100g) 21 (12, 49) 24 (13, 33) 0.05
Phosphorus:Protein
(mg P/g Pro) 11.6 (6.9, 19.9) 9.9 (7.2, 27.9) 0.02
abc Medians significantly different by Mann-Whitney and p<0.05 if subscripts differ from each other
†Kruskal-Wallis test
*Includes foods from seafood counter where an ingredient list was not available
Comments: Minimally processed foods were defined as an unprocessed food altered in ways that
do not add or introduce any substance, and usually subtract parts of the food, without
significantly changing its nature and/or use (Moubarac et al, 2014). Since this definition is in line
with our definition for reference foods (as a fresh MPF item that contained no additional
ingredients or additives), we combined reference foods and minimally processed foods for the
purpose of this analysis.
The minimally processed food group included all fresh chicken breast, ground beef, steak,
tilapia, some sole products, plus reference products. The processed foods group tended to be
completed different types of MPF (i.e. bacon, deli ham, frozen chicken breast, chicken strips,
rotisserie chicken, beef burger, shrimp and some sole products). Thus, we did not feel it was
methodologically sound to compare two groups containing completely different types of MPF.
Carrigan et al (2014) have previously chemically analyzed a low-additive minimally processed
4-day menu compared to an additive-rich processed 4-day menu and determined that the
processed diet contained 60% more phosphorus.
135
Appendix H
Comparison of Analyzed Nutrient Content Among
Breaded Chicken Products
136
Comparison of Analyzed Nutrient Content Among Breaded Chicken Products
Comments: Breaded chicken was identified as a major source of phosphate additives (Lampila, 2013),
and occupies a substantial amount of shelf space at the grocery store, therefore we decided to chemically
analyze these products. However, as the frequency of consumption of breaded chicken was not ranked as
high as other types of MPF, we did not include breaded chicken products in the analysis of commonly
consumed MPF. Similar to other types of MPF, breaded chicken with phosphorus additives appear to
have higher phosphorus content, in amounts that are in line with the packaged chicken strips and frozen
chicken breast products that were analyzed.
Protein
(g/100
g)
Phosphorus
(mg/100g)
Potassium
(mg/100g)
Sodium
(mg/100g)
P:Pro
(mg P/1 g
Pro)
PO4
additives
(Y/N)
Compliments
Chicken Strips,
Breaded cutlets
10.91 260 210 570 23.8 N
Maple Leaf Prime
Chicken Strips,
Breaded
18.11 310 300 800 17.1 Y
President’s Choice
Chicken Breast
Fillets, Breaded
15.57 290 470 450 18.6 Y
Irresistibles
Chicken Breast
Fillets, Breaded
15.58 200 280 370 12.8 N
137
Appendix I
The accuracy of Canadian Nutrient File data for reporting
phosphorus, potassium, sodium and protein
in commonly consumed meat, poultry and fish products
138
The accuracy of Canadian Nutrient File data for reporting phosphorus, potassium, sodium
and protein in commonly consumed in meat, poultry and fish products
The Canadian Nutrient File (CNF) is a comprehensive food composition database
containing average values of chemically analyzed nutrients for foods (CNF User’s Guide, 2010).
Clinicians often use the CNF as a point of reference for the purposes of assessing dietary intake,
monitoring population-wide nutrition programs and menu planning (CNF User’s Guide, 2010).
Approximately 59% of data in the CNF is unchanged from the U.S Department of Agriculture
(USDA) nutrient database, while the remaining is periodically modified to reflect differences
specific to the Canadian food supply (CNF User’s Guide, 2010). The purpose of this study was
to examine if nutrient data obtained from chemical analyses of commonly consumed meat,
poultry and fish (MPF) foods was comparable to nutrient data in the CNF.
We administered a modified version of the Diet History Questionnaire II, adapted for
Canada from the National Institute of Health (Csizmadi et al, 2007) to patients (n=67) receiving
hemodialysis and peritoneal dialysis in Toronto, Canada from July to September 2013.
Unbreaded chicken, ground beef, steak, beef burgers, white fish, shrimp, deli ham and bacon
were identified as the most commonly consumed MPF foods. MPF foods (n=91) from twelve
subtypes were purchased from the top 3 grocery store chains in Canada and cooked. Protein,
sodium, phosphorus and potassium content were analyzed using the Association of Analytical
Communities (AOAC) official methods 992.15 and 984.27. Discrepancies were defined as CNF
values that differed by more than two standard deviations from the mean analyzed value.
Comparable foods in the CNF database (2010) were available for 10 of 12 subtypes of
MPF foods (n=71). Based on our definition, 30% of foods had discrepancies in sodium, 60% in
potassium, 50% in phosphorus and 40% in protein between CNF and analyzed foods (See
Table). It should be noted that 60% of the CNF values were based on food analysis conducted
prior to 2000, dating as far back as 1981. All CNF values except for the nutrient content of steak
and the protein content of chicken breast originated from the USDA nutrient database. While the
CNF contains sources of foods from across Canada, our results were limited to foods purchased
in Toronto, Canada.
139
Importantly, a reasonable level of accuracy in CNF values is needed for nutrients such as
potassium and phosphorus, which are not required to be listed on the Nutrition Facts Table
(Health Canada, 2004). Our results demonstrate rather large discrepancies between analyzed and
CNF values. For example, fresh skinless chicken breasts contained on average almost twice the
amount of potassium stated in the CNF (236 vs. 438 mg/100g), which translates into an error of
two servings of a high potassium food instead of one (Sanghavi et al, 2013). This information
impacts those who require a dietary potassium restriction such as those with kidney disease and
others with impaired urinary potassium excretion (IOM, 2005). In addition, the CNF database
lacked comparable foods for newer food items such as, unbreaded chicken strips and frozen
chicken breast, which occupy substantial amounts of shelf space.
In conclusion, we found considerable discrepancy in the sodium, potassium, phosphorus
and protein content listed in the CNF versus the chemically analyzed nutrient content of
commonly consumed MPF foods by patients with CKD. Our results highlight the need for
further studies to verify and extend these analyses to more foods in order to more accurately
reflect the nutrient value of current food supply in Canada. This initiative would enable patients
to be better able to make informed and appropriate food choices that are in compliance with their
dietary requirements.
140
Comparison of the nutrient content of chemically analyzed foods versus data for
comparable foods from the Canadian Nutrient File (CNF)
Food subtypes Data Source Year n Na K P Pro
Unbreaded Chicken
Chicken breast,
Fresh, Skinless
Analyzed 2014/15 8 55 (10) 438 (36) 255 (21) 28 (1)
CNF #892 1996 - 51 236* 217 30
†
Chicken, Rotisserie Analyzed 2015 5 306 (90) 360 (26) 200 (12) 27 (1)
CNF #6648 2009 12 381 245* 248
* 18
*
Lean Ground Beef,
Fresh
Analyzed 2015 6 70 (9) 383 (39) 213 (20) 23 (2)
CNF #2685 1988 - 64 291* 162
* 30
*
Top Sirloin Steak,
Fresh
Analyzed 2015 6 65 (8) 458 (23) 263 (8) 30 (2)
CNF # 6144 2006 6 58 351* 219
* 29
Beef Burger, Frozen Analyzed 2015 7 464 (73) 296 (50) 183 (29) 18 (4)
CNF #2704 1988 2 77
* 305 174 23
White Fish
Tilapia Analyzed 2015 6 58 (37) 390 (51) 205 (14) 20 (2)
CNF # 5967 2006 2 56 380 204 26*
Sole Analyzed 2015 7 301 (113) 158 (70) 280 (108) 17 (2)
CNF #0307 1989 - 105
≠ 344
*≠ 289
≠ 24
*
Shrimp Analyzed 2015 7 510 (127) 58 (50) 199 (62) 15 (3)
CNF #3211 1989 >25 148* 185
* 205 20
Deli Ham Analyzed 2014/15 11 993 (58) 551 (317) 251 (37) 16 (3)
CNF #1149 1981 - 1304
* 287 153
* 17
§
Bacon Analyzed 2014/15 8 1625 (658) 355 (133) 301 (115) 31 (11)
CNF #5406 2003 4 2073 498 480
* 39
Values for analyzed and reference foods are expressed as mean (SD)
Abbreviations: CNF = Canadian Nutrient File; Na = Sodium, K = Potassium, P = Phosphorus, Pro =
Protein
*Indicates that the mean chemically analyzed value differed significantly from the CNF value by more
than two standard deviations
†n = 16 products
≠ n = 11 products
§ n = 2 products