Metabolism of Carbohydrates: Implications for Health

Janine Higgins, PhDUniversity of Colorado Denver

Dietary Recommendations Enjoy a wide variety of nutritious foods• Eat plenty of vegetables, legumes and fruits• Eat plenty of cereals, preferably wholegrain• Include lean meat, fish, poultry and/or alternatives• Include milks, yoghurts, cheeses – choose low fat• Drink plenty of waterand take care to:• Limit saturated fat and moderate total fat intake• Choose foods low in salt• Limit your alcohol intake if you choose to drink• Consume only moderate amounts of sugars and

foods containing added sugars

Dietary Recommendations Enjoy a wide variety of nutritious foods• Eat plenty of vegetables, legumes and fruits• Eat plenty of cereals, preferably wholegrain• Include lean meat, fish, poultry and/or alternatives• Include milks, yoghurts, cheeses• Drink plenty of waterand take care to:• Limit saturated fat and moderate total fat intake• Choose foods low in salt• Limit your alcohol intake if you choose to drink• Consume only moderate amounts of sugars and

foods containing added sugars

Cochrane Database Syst Rev. 2011 Jul 6;(7):CD002137. Reduced or modified dietary fat for preventing cardiovascular disease. Hooper L, Summerbell CD, et al.“Small but important reduction in cardiovascular risk for reduction of saturated fat, but not reduction of total fat, in longer trials”

Dietary Recommendations Enjoy a wide variety of nutritious foods• Eat plenty of vegetables, legumes and fruits• Eat plenty of cereals, preferably wholegrain• Include lean meat, fish, poultry and/or alternatives• Include milks, yoghurts, cheeses• Drink plenty of waterand take care to:• Limit saturated fat and moderate total fat intake• Choose foods low in salt• Limit your alcohol intake if you choose to drink• Consume only moderate amounts of sugars and

foods containing added sugars

J Int Med Res. 2010 Mar-Apr;38:318-85.Nutritional profiles in a public health perspective: a critical review.Foltran F, Verduci E, et al.“Evidence linking a reduced fat intake with cardiovascular mortality and obesity is generally non-significant.”

Dietary Recommendations Enjoy a wide variety of nutritious foods• Eat plenty of vegetables, legumes and fruits• Eat plenty of cereals, preferably wholegrain• Include lean meat, fish, poultry and/or alternatives• Include milks, yoghurts, cheeses• Drink plenty of waterand take care to:• Limit saturated fat and moderate total fat intake• Choose foods low in salt• Limit your alcohol intake if you choose to drink• Consume only moderate amounts of sugars and

foods containing added sugars

Dietary Recommendations Enjoy a wide variety of nutritious foods• Eat plenty of vegetables, legumes and fruits• Eat plenty of cereals, preferably wholegrain• Include lean meat, fish, poultry and/or alternatives• Include milks, yoghurts, cheeses• Drink plenty of waterand take care to:• Limit saturated fat and moderate total fat intake• Choose foods low in salt• Limit your alcohol intake if you choose to drink• Consume only moderate amounts of sugars and

foods containing added sugars

Cochrane Database Syst Rev. 2011 Jul 6;(7). Reduced dietary salt for the prevention of cardiovascular disease. Taylor, Ashton, et al. 665 deaths in some 6,250 participants: “No strong evidence of benefit of salt restriction on all cause or cardiovascular mortality in normal or hypertensive patients”

Dietary Recommendations Enjoy a wide variety of nutritious foods• Eat plenty of vegetables, legumes and fruits• Eat plenty of cereals, preferably wholegrain• Include lean meat, fish, poultry and/or alternatives• Include milks, yoghurts, cheeses• Drink plenty of waterand take care to:• Limit saturated fat and moderate total fat intake• Choose foods low in salt• Limit your alcohol intake if you choose to drink• Consume only moderate amounts of sugars and

foods containing added sugars

Dietary Recommendations Enjoy a wide variety of nutritious foods• Eat plenty of vegetables, legumes and fruits• Eat plenty of cereals, preferably wholegrain• Include lean meat, fish, poultry and/or alternatives• Include milks, yoghurts, cheeses• Drink plenty of waterand take care to:• Limit saturated fat and moderate total fat intake• Choose foods low in salt• Limit your alcohol intake if you choose to drink

Av. Aus intake = 9.8L/y or 188mL/wk = < 2 glasses wine/wk

• Consume only moderate amounts of sugars and foods containing added sugars

BMJ. 2011 Feb 22;342:d671. doi: 10.1136/bmj.d671. Association of alcohol consumption with selected cardiovascular disease outcomes: a systematic review and meta-analysis. Ronksley PE, Brien SE, et al.“Moderate alcohol consumption is associated with a reduced risk of multiple cardiovascular outcomes. Dose-response analysis revealed that the lowest risk of coronary heart disease mortality occurred with 1-2 drinks a day”

Dietary Recommendations Enjoy a wide variety of nutritious foods• Eat plenty of vegetables, legumes and fruits• Eat plenty of cereals, preferably wholegrain• Include lean meat, fish, poultry and/or alternatives• Include milks, yoghurts, cheeses• Drink plenty of waterand take care to:• Limit saturated fat and moderate total fat intake• Choose foods low in salt• Limit your alcohol intake if you choose to drink• Consume only moderate amounts of sugars and

foods containing added sugars

Added/Simple Sugars• Glucose and fructose (sucrose) most

commonly consumed- In USA, adults consume ~23 tsp (120g) of added sugar/d; from soft drinks, juice, desserts (pastries, pies), and lollies- 9% of energy from fructose, 10% from sucrose (total 19%)- In UK, ~16% of total energy from sucrose

• Glucose and fructose are metabolized differently and have different metabolic effects

waste out

food in

xx x x

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x

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x x^^x ^

x

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Rapidly Digested Starch Slowly Digested Starch

Resistant Starchx

^ Glucose

Fructose

Lactate

TG

CO2

Glucose (50%)

Lactate (25%)TG

Glycogen (15%)

Fructose vs Glucose• Liver:

- Increases gluconeogenesis- Increases de novo lipogenesis- Causes insulin resistance- Increases intracellular lipid

• Whole Body:- Increases TG production- Decreases TG clearance- Decreases plasma FFA – lower adipocyte

lipolysis

Daly et al (2000) Am J Clin Nutr 71: 1516.

Higher CHO ox’n after sucrose meal than starch meal

FROM SUCROSE: Higher fructose ox’n, delayed glucose ox’n

N=722-68 yo, healthyCrossover design

Fructose Increases CHO Oxidation

Brown et al (2000) Am J Physiol 294: R730.

Fructose caused higher CHO ox’nNo change in TEE Lower fat oxidation

Higher CHO ox’n after sucrose meal than starch meal

FROM SUCROSE: Higher fructose ox’n, delayed glucose ox’n

Fructose Increases CHO Oxidation

Sucrose Decreases Fat Oxidation

Daly et al (2000) Am J Clin Nutr 71: 1516.N=722-68 yo, healthyCrossover design

Total CHO Intake Is Associated with Lower BMI

Gaesser, J Am Diet Assoc. (2007) 107:1768

NHSII 26 23N=90,655

HPFS 26.1 24.8N=39,926

Sugar Intake Is Associated with Higher Adiposity

Davis et al, Am J Clin Nutr. (2007) 86:1331

N=12010-17 yo, overweight24 h diet recalls

• Total sugar (g/d) positivelycorrelated with body mass index (BMI; in kg/m2), BMI zscores, and total fat mass (r 0.20, r 0.22, and r 21)

• Total sugar (g/d) negatively correlated with SI (r0.29)

• Dietary fiber, glycemic index, and glycemic load were not correlated with adiposity or insulin dynamics before or after control for covariates.

Large epidemiological studies• Multiple large studies – generally no

association between high fructose corn syrup intake and body weight or obesity

• Difficult to interpret data– ↑ intake of artificial sweeteners is in obese; ↑

intake of sucrose is in the most lean individuals– No relationship between regular soft drink intake

and obesity or BMI; positive association of diet soft drink intake with obesity and BMI

Sucrose impairs insulin action at liver not peripheral tissue – Rat study

Storlien et al (1988) Am J Clin Nutr 47: 420Rat study

No significant change in glucose uptake in isolated muscle or adipose tissues.

Rats 2

• Relative to chow, both high sucrose and high cornstarch diet:– decreased glucose uptake in muscle– increased intramuscular triglyceride– increased visceral fat with no change in

total body weight– increased fasting insulin

Kim et al, Am J Physiol. (1999) 276:R665

Human Data

• High fructose ingestion for one or 10 weeks caused insulin resistance vs glucose

• Moderate fructose intake for 4 wk increased TG but did not impair insulin action

• Fructose and sucrose have similar effects

Fructose Increases Circulating TG

Stanhope et al (2009) J Clinical Invest 119: 1322.N=7Overweight/obese postmenopausal25% of daily energy from sweetened drinks

Fructose Increases Blood Pressure in Healthy Adults

Brown et al (2000) Am J Physiol 294: R730.

Fructose causes increased systolic and diastolic BP - due to increased cardiac output, no change in peripheral vasodilation

N=1521-33 yo, healthyCrossover design

Conclusions• Simple sugars are absorbed and

metabolized differently from starches• To impact health outcomes need to

consider CHO quality NOT just quantity– quality is more than simple vs complex

• Fructose has several negative impacts on metabolism vs glucose or starch

• Large epidemiological studies cannot provide meaningful data to demonstrate benefits/risks of simple sugar consumption.

• Limit simple sugars? • How about focusing on limiting total

caloric intake???

Thanks to:Troy DonahooPaul MacLeanIan BrownCCTSI Nutrition

Core