Measuring Diet Chapter 3

Chapter 3 Measuring Diet

• The chapter outlines reasons for measuring diet, techniques, considerations for specific groups, issues in dietary measurement, and estimating portion size.
• The first topic covers the reasons for measuring diet, including assessing food and nutrient intake, trends in food/nutrient intake, formulating and evaluating government health policy, and commercial purposes for food manufacturers.
• The second topic details techniques in measuring diet. Techniques include the "BIG THREE": 24-hour recall, food records (or food diaries), and food frequency questionnaires, while less common methods include diet history, duplicate food collections, food accounts, food balance sheets, telephone interviews, and technological innovations.

Topic 1: Reasons for Measuring Diet

• Reasons for assessing and monitoring food and nutrient intake include adequacy of diet intake and malnutrition; food supply monitoring; trends in food/nutrient intake; food additive & contaminants evaluation; and formulating and evaluating government health and agricultural policy.
• Other reasons for measuring diet are related to target food assistance programs, food guides, regulations and establishing nutrition education programs and its success.
• Considerations also include conducting epidemiological research, identifying populations at risk of diet-disease relationships, and assessing commercial purposes for food manufacturers.
• The goal is to improve human health through proper dietary assessment.

Topic 2: Techniques for Measuring Diet

• Key techniques for measuring diet include the "BIG THREE": 24-hour recall, food records (or food diaries), and food frequency questionnaires.
• Less common techniques are diet history, duplicate food collections, food accounts, food balance sheets, other considerations (telephone interviews), and technological innovations.
• Daily techniques include food records and 24-hour recalls. Usual or average intake is determined via diet history and food frequency questionnaires. Different formats for questionnaires are meal-based or list-based.

24-Hour Recall

• Detailed: A trained interviewer asks the respondent to recall everything eaten and drank from the previous 24 hours, sometimes a longer period.
• The interviewer provides assistance in estimating portion sizes and prompts about the previous day's activities to aid the respondent's memory. Errors or omissions are checked afterwards.
• Technique 1: Recalling everything eaten and drank from the time the person woke up that day until the present to the time the interview took place.
• Technique 2: Recalling everything eaten and drank from midnight of the previous day to midnight of the previous day. The techniques may include a demonstration.
• Strengths: Inexpensive, quick (less than 20 minutes), detailed on specific foods, short-term memory reliant, low respondent burden, high acceptability, does not alter diet.
• Limitations: May have withholding information, underreporting of certain things or overreporting of others, missing or phantom foods, and "flat-slope syndrome" (intra-individual variability).

Multiple-Pass Method

• The interviewer reviews the previous day’s intake multiple times
• Process: quick list, detail, review
• Computer assisted 5-Step Method (AMPM): used in NHANES, quick list, forgotten foods, details, review, and final probes. The process takes 30-45 minutes to complete.
• Interview training is thorough; underreporting is fairly low (10% males, 12% females, 3% normal weight).
• An internet-based version of AMPM is available.

USDA's Automated Multiple-Pass Method (AMPM)

• Detailed description of the design steps and memory cues for the AMPM method.

24-Hour Recall, Additional Considerations

• Variability between individuals, rare foods, capturing intake across seasons, how many days needed to collect data, and nutrients of interest/sample size and validity/reliability levels are important.
• Day-to-day variability on intake distributions. Graphs illustrate varying amounts of single-day, 2-day mean, and usual intakes.

Food Record (Diet Record, Food Diary)

• Strengths: Limits recall bias, provides individual food details, captures other eating habits, allows for quantitative accuracy, multiple days can increase accuracy (esp. different seasons).
• Limitations: Requires literacy and effort; agreement on respondent representativeness may not happen; fatigue can occur, especially after multiple days, change(s) in eating habits, reactivity (30-50% admit), and data entry/analysis is laborious.

Food Frequency Questionnaire (FFQ)

• How often one consumes a limited number of foods; food lists must be targeted to the population of interest; foods and nutrients in the population should also be considered; 150 foods or less; frequency (daily, weekly, monthly, yearly); sometimes estimated typical size/standard amount is assumed; answer marking on a scannable, machine-readable sheet.
• Forms: Simple (nonquantitative), semiquantitative, quantitative.

FFQ: Additional Considerations

• Screening tools for calcium, fat, fruit/vegetables, fiber; when whole diet assessment is not needed or when cost is a concern are important reasons for using them; use is not typically a substitute for entire diet assessment

Topic 3: Considerations for Certain Groups

• Considerations for assessing various specific demographics, including young people (under 8 years old requiring a caregiver) and those with specific recall difficulties.
• Considerations include those with memory problems, vision or hearing impairment, and low literacy. These individuals often require specialized tools or strategies such as large print, Braille, audio aids, interpreters, models, or easily understood vocabularies.

Topic 4: Issues in Dietary Measurement

• Validity is the instrument's ability to accurately measure what it intended to measure. Validity categories include relative/criterion validity, comparing new instruments with gold standards, and face validity – where expert reviews are needed.
• Biological markers are useful for measuring intake data against, including urinary nitrogen, urinary sodium, plasma carotenoids, and vitamins E and C.
• Energy expenditure for a person depends on their weight and maintenance levels from an equation. Measuring deuterium and oxygen-18 in urine can be used to measure energy expenditure.
• Reliability is the ability to produce similar estimates on multiple occasions in a study.
• High validity/reliability is desired, and graphs illustrate different forms of reliability and validity.

Topic 5: Estimating Portion Size

• Survey participants can use geometric shapes representing different foods, with known dimensions (surface area or thickness). Models from poster board or other materials can be used to demonstrate the sizing.
• Photographs can assist respondents in accurately estimating food portion size.
• USDA Food Model Booklet can be used, which provides figures (with links) for measuring portion sizes using measuring tools and lifelike models.

Other Measurement Techniques

• Diet history, duplicate food collection, food accounts, site visits, and food balance sheets. (strengths, limitations are detailed for each)

Technological Improvements

• Digital imaging, online AMPM, ASA24, DHQ, digital cameras, and wearable cameras. Fiducial markers can be used as well.
• Advantages: Low burden, high validity, low reactivity. Disadvantages: Cost, photo quality, similar appearing foods.

General Considerations

• Different assessment instruments ("Big Three", Multiple Pass Methods, Food frequency questionnaires, Diet History, etc.) have varying strengths and weaknesses, including time required, logistical hurdles, and potential reactivity.

This quiz covers Chapter 3 on measuring diet, discussing the importance of assessing food and nutrient intake. Key techniques such as 24-hour recall and food diaries are explored, along with considerations for various population groups. Dive into the complexities of dietary measurement and its implications for health policies.