assessing dietary intakes in food environment research: implications for policy and practice

Assessing dietary intakes in food environment research:

Implications for policy and practice

SHARON KIRKPATRICK University of Waterloo

JILL REEDY, KEVIN DODD, AMY SUBAR, FRAN THOMPSON, ROBIN MCKINNONUS National Cancer Institute

EBONEÉ BUTLER University of North Carolina at Chapel Hill

Assessing dietary outcomes in food environment research

Food environmen

tDiet

Body weight and other

risk factors

Incidence of chronic diseases

The food environment, diet and health


The food environment, diet and health

Lytle L, AJPM 2009


Recent reviews highlight a lack of consensus in the existing literature


► Context

► Measures of the food environment: Capturing different aspects, e.g., density or distance to a

particular type of food outlet, variety and quality of in-store offerings, perceived availability of food in a particular area

Error

► Measures of dietary intake: Capturing different aspects, e.g., whole diet versus particular

foods or food groups Error

What might account for inconsistencies in the evidence?


► Context

► Measures of the food environment: Capturing different aspects, e.g., density or distance to a

particular type of food outlet, variety and quality of in-store offerings, perceived availability of food in a particular area

Error

► Measures of dietary intake: Capturing different aspects, e.g., whole diet versus

particular aspects of diet Error

What might account for inconsistencies in the evidence?


► Widely recognized that data collected using self-report dietary instruments contain substantial bias

► Bias can: Mask relationships that actually exist Result in spurious effects

− Particularly problematic if differential error among populations (e.g., low versus high income)

Reduce statistical power

Measuring dietary outcomes in food environment research

Barrier to policy and program interventions


Methods for assessing diet

Recall or record Food frequency questionnaire

Brief instrument(screener)

less

more

more

more

more

more

less

less

less

less

Bias

Number of dietary factors

Distribution of dietary factors

Time

[Money]



► 24 hour recalls and food records

► Food frequency questionnaires


► Brief instruments focused on ‘indicator foods’ (e.g., fruits, vegetables, salty or sugary snacks) Screeners or checklists

1 or 2 questions (e.g., how many servings of fruit/vegetables do you usually eat each day?)



► What is the state of food environment research in terms of assessment of dietary outcomes?

► Review of peer-reviewed literature published from January 2007 through June 2012 Food environments include food stores, restaurants, schools,

home, farmers’ markets, recreational facilities, etc.

Research question and method

Kirkpatrick et al., AJPM, 2014


► Systematic search Search engines:

− PubMed, SCOPUS, PsycInfo, Web of Science Search terms:

− [Food or nutrition or diet] AND [environment or community or neighborhood or neighbourhood] AND [measure] AND [assess]

− Food environment

► Measures of the Food Environment web compilation (appliedresearch.cancer.gov/mfe)

► Literature cited by each article

Search strategy


2450 unique articles identified and screened

368 abstracts reviewed to assess eligibility

149 full-text articles assessed for eligibility

51 articles included in systematic review

2082 articles excluded after initial screen

219 articles excluded after review of abstracts

111 articles excluded after full-text review

13 additional articles identified via the reference lists of included articles and relevant reviews and the Measures of the Food Environment website

38 eligible articles identified


24-hour recall

Record/Diary

FFQ Screener 2 items 1 item0

5

10

15

20

25

30

35

40

% o

f arti

cles

Dietary assessment in food environment research (n=51)


24-hour recall

Record/Diary

Food frequency questionnaire Screener Two Items Single Item

Fruit and/or Vegetables (n=35)

Sugar-sweetened beverages(n=14)

Fast Food(n=9)

Diet Quality(n=9)

Note:- The count of instruments exceeds the number of studies reviewed because one or more studies used multiple instruments.- The outcomes included are those most commonly examined among the studies reviewed. Note that a single study may include multiple outcomes and so the sum of studies examining unique outcomes exceeds the total number of studies reviewed.



► Tendency toward the use of brief (more error-prone) assessment instruments Low cost and respondent burden Results in focus on ‘indicator foods’ (or due to a priori

interest in specific food groups?)



► Existence of bias in dietary data and the potential implications for study results rarely discussed

► In several papers, it was noted that the dietary assessment tool was ‘validated’ Validity often assessed by comparing the instrument to

another self-report instrument limited utility



► Relationships between food environment features and dietary outcomes more consistent in studies using less error-prone measures


Studies with 24HR, diaries, FFQ

• 76% showed overall effects in the expected direction

Studies with screeners, 1-2 items

• 55% showed overall effects in the expected direction


► Explosion of research examining relationships between features of food environments and dietary intakes

► Bias in dietary data may be substantial, particularly if estimates are based on brief dietary instruments May lead to spurious effects and reduced statistical power to

detect associations

► Barrier to establishing policy and program interventions to improve diet and health

Conclusions


► Effects of bias when diet is the outcome (rather than an exposure) not thoroughly examined – need more research to inform strategies

► In the meantime? Start with the best instrument possible: technologic

advances allow collection of more detailed and less biased dietary data

Use available strategies to reduce the effects of error (e.g., calibrate data from brief instruments using other sources)

Discuss potential implications of bias on study results and inconsistencies with other studies

Moving forward


Questions or comments?

[email protected]

assessing dietary intakes in food environment research: implications for policy and practice

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