Data Capture
Mode of Administration
- Typically interviewer-administered, either face-to-face or by telephone, but may be self-administered.
- Format can be either on paper or electronic (Learn More about Technology in Dietary Assessment).
Population Considerations
- Appropriate for a variety of eating cultures.
- If interviewer-administered, appropriate for groups with literacy challenges.
- Relies on [glossary term:] specific memory and requires respondent (or [glossary term:] surrogate) to be able to report all foods and beverages consumed in the past 24 hours or on the previous day from midnight to midnight.
- Some groups cannot answer for themselves (for example, children or some people with disabilities). Proxy reporting is possible, but data collected may be limited by knowledge of the [glossary term:] surrogate reporter (Learn More about Surrogate Reporting).
Resource Requirements
- Data entry system is required, typically either paper or electronic. For NCI's ASA24, access to high-speed Internet is required.
- Interviewer-administration requires highly-trained interviewer; self-administration requires completely self-explanatory interface.
- Aids that portray different portion sizes may enhance [glossary term:] accuracy of report.
Study Design Considerations
For greater detail on the following issues when considering whether to use a 24HR to answer a particular research question, see Choosing an Approach for Dietary Assessment.
General Considerations
- Recalls should be unannounced so as to avoid potential [glossary term:] reactivity bias.
- The number of recalls needed per person depends on the research question.
- The population's diet can differ systematically by factors called [glossary term:] nuisance effects, such as day of week (Learn More about Day-of-Week Effect), season (Learn More about Season Effect), and sequence for multiple administrations. For all research objectives, these nuisance effects should be considered in design and/or analysis.
- The collection of [glossary term:] recovery biomarkers in a subsample of participants should be considered; these can be used as [glossary term:] reference instruments to reduce [glossary term:] bias for some nutrients.
Guidance for Specific Research Objectives
- If your research objective is to estimate [glossary term:] mean intakes of a group, a single recall per person is sufficient.
- If your research objective is to estimate [glossary term:] usual dietary intake distributions for a group (for example, for the purpose of examining percentiles or estimating the proportion above or below some threshold), at least two non-consecutive recalls are needed among at least a portion of the group to correct for [glossary term:] day-to-day variation (a source of [glossary term:] within-person random error) (Learn More about Usual Dietary Intake).
- If your research objective is to analyze the [glossary term:] association between diet as an [glossary term:] independent variable and another variable (e.g., diet at baseline and later onset of cancer), a single 24HR can be used as the [glossary term:] main dietary assessment instrument, but at least two and up to six non-consecutive 24HRs are preferable. The additional recalls allow correction for day-to-day variation in analyses and thus provide more [glossary term:] precision in estimates of individual intake.
- If your research objective is to analyze the association between one or more independent variables (e.g., socioeconomic status) and diet as a dependent variable, variables known to affect quality of report, such as body mass index, should be assessed and later included as [glossary term:] covariates in analyses.
- If your research objective is to analyze change in dietary intake as a result of an [glossary term:] intervention (e.g., to evaluate the effectiveness of an educational program to encourage fruit and vegetable intake), it is important to consider the potential for [glossary term:] differential response bias between study groups (i.e., whether the bias in each group is similar or different). This is of concern in intervention studies because [glossary term:] exposure to the intervention itself can create differential error in reporting in the treatment group(s) relative to the control group.
- If your research objective is limited to assessing changes in mean intake of the study groups over time, a single recall at each relevant time may be sufficient. Furthermore, if, at baseline, assignment to the intervention and control groups is randomized, and if thus you assume that the pre-intervention mean intake does not significantly differ between the two groups, the difference between the two groups in post-intervention mean intake may be ascribed to the intervention.
- If your research objective is to compare usual dietary intake distributions between the control and intervention groups, multiple recalls are required.
A larger number of recalls per person may be needed to examine dietary components that are [glossary term:] episodically consumed (for example, Vitamin A, dark green vegetables) as opposed to those that are [glossary term:] non-episodically consumed (for example, protein, total grains).
Alternatively, the 24HR can be used as a [glossary term:] reference instrument when a less detailed instrument, such as an [glossary term:] FFQ, is used as the main instrument. In such cases, a 24HR (preferably more than one) is collected from a subsample to allow for regression [glossary term:] calibration of the less detailed instrument (this is called an [glossary term:] internal calibration sub-study). Alternatively, data from an external source (called an [glossary term:] external calibration study) can be used (Learn More about Calibration).
To avoid the effects of these potential biases, an objective measure, such as serum carotenoids as a marker for fruit and vegetable intake, could be considered. In addition, collecting and adjusting for other non-dietary self-report information (e.g., social desirability scale) may help characterize individuals who may be more prone to [glossary term:] response bias (Learn More about Social Desirability).