Chapter 3: Measuring Diet

Study Notes

Reasons for Measuring Diet: Assessing and monitoring food and nutrient intake, evaluating diet adequacy, and identifying trends in food intake. This also includes evaluating food supply and identifying food additives and contaminants. Policies and programs regarding agricultural policy, planning food production, and food assistance are also considered.
Techniques in Measuring Diet: Common techniques include 24-hour recall, food records (diaries), and food frequency questionnaires. Less common methods include diet history, duplicate food collections, and food accounts as well as food balance sheets. Other considerations include telephone interviews and technological innovations.
Considerations for Certain Groups: Techniques must be adapted to different populations by considering things like interview training and other issues.
Issues in Dietary Measurement: Includes issues like intra-individual variability, multiple days required to get accurate data, and the need to avoid biased information from the participant.
Estimating Portion Size: Methods to estimate portion sizes, including asking about previous day's activities to recall, and adjusting for estimations. This may be measured for research purposes.

Reasons for measuring diet include exploring relationships between diet and disease, identifying populations at risk for diet-related illness, and evaluating the success of nutrition education programs.
Commercial purposes as well as food manufacturer interests also drive measuring diet.

24-Hour Recall: A technique where a trained interviewer gathers information about everything eaten and drunk by the subject over a 24-hour period. The goal is to capture a complete overview of consumption.
Food Records (Diaries): Respondents record their food and beverage intake as they eat it. This often runs from 1 to 7 days.
Food Frequency Questionnaires: Subjects respond to questions about how often they eat different foods. These are questionnaires with pre-determined food lists.
Diet History: Uses a detailed format to gather data on the subject's dietary information over time. Collected and analyzed data involves specific details of food choices and other eating habits.
Other Methods: Includes duplicate food collections, food accounts, food balance sheets, telephone interviews, and other technological innovations.

Daily Food Record: A daily record for gathering detailed information on an individual's intake of food over one to seven days.
24-Hour Recall: A 24-hour recall involves the trained interviewer asking the subject to recall everything they ate and drank on the day of the interview.
Diet History: A method where the interviewer gathers detailed information on the subject's dietary patterns over time.
Food Frequency Questionnaires: Subjects record how often they eat specific foods.

Technique 1: Recalling entire intake from the moment the subject woke up until now.
Technique 2: Recalling everything eaten and drunk from midnight to midnight the previous day.
Interviewer's Role: A trained interviewer guides the respondent to recall all information. This often includes prompts to clarify food details, portion sizes, and specific attributes of consumed foods.
Strength: Inexpensive and quick. Provides detailed information. Allows for less respondent burden compared to other methods.
Limitations: May suffer from underreporting, missing or incorrectly reporting foods, and recall bias.

Method: The purpose is to lower the rate of underreporting and uses multiple rounds to have the participant review previous intake.
Process: Encompasses quick list, details, review and a final probe.
Steps: Includes gathering a quick list of items to clarify, details of each food and drink, reviewing previous items and a final probe asking if there is anything else.
Strengths: Helps to reduce underreporting and provides thorough information.
Limitations: Can take 30-45 minutes to complete.

Strength: Useful to identify daily dietary patterns. It also includes the ability to capture individual details regarding food and eating habits.
Limitations: Requires literacy and effort from the participant.
Considerations: Ensuring representative sampling, fatigue, compliance rate ("Change eating habits": 30-50% admit; Reactivity), data entry/analysis.
Other details: Multiple days (with spacing between) can increase accuracy.

Factors like intra-individual variability, need for multiple days and using this method in various seasons need to be considered when evaluating 24-hour recalls.
Sample size consideration of the population under review.
Degrees of within-individual or between-individual variability may also need to be calculated.