Data Capture

Mode of Administration

Population Considerations

Resource Requirements

  • Data collection can be conducted using paper, the Internet, electronic devices, or other devices.
  • Written instructions and/or in-person training of the respondent are necessary. Training may be preferable, especially for low-literacy or less motivated respondents.
  • For measured records, either a scale or common household measures must be provided. If a scale is used, it should be routinely checked for [glossary term:] accuracy.
  • For records collected electronically, devices may need to be provided. For smartphones, usage costs may require compensation.

Study Design Considerations

General Considerations

  • Because of reactivity, data from food records may be biased, so this should be considered in the study design and interpretation of results. Further research is needed before specific guidance can be provided on the use of food records for various research objectives. Nonetheless, it is likely that many considerations applicable to 24HRs, such as the need for non-consecutive repeats for the estimation of usual intake distributions, also apply to food records.
  • The number of [glossary term:] n-day records 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 Effects), 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 n-day record per person is sufficient.
  • If your research objective is to estimate usual dietary intake distributions for a group (e.g., in order to examine percentiles or estimate the proportion above or below some threshold), multiple records are needed to correct for [glossary term:] day-to-day variation (a source of within-person random error). Because of [glossary term:] correlations between intakes on consecutive days, a single n-day record of consecutive days is less useful than multiple non-consecutive n-day records for this purpose.
  • 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 n-day food record can be used as the [glossary term:] main dietary assessment instrument, but collecting at least two non-consecutive n-day food records is preferable. The additional records allow correction for day-to-day variation in analyses and thus provide more [glossary term:] precision in estimates of individual intake using [glossary term:] regression calibration.
  • Alternatively, the food record 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 food record (preferably more than one) is collected from a subsample to allow for [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).
  • If your research objective is to analyze the association between one or more independent variables (e.g., socioeconomic status) and diet as a [glossary term:] dependent variable, the potential for [glossary term:] differential response bias should be considered. This would be especially problematic if the main independent variable has been found to be associated with dietary reporting error (e.g., body weight).
  • If your research objective is to analyze change in diet as the result of an intervention (e.g., to evaluate the effectiveness of an educational program to encourage fruit and vegetable intake), food records are not recommended because of the potential for bias. The process of recording intake has the potential to create reactivity. In addition, [glossary term:] differential response bias between study groups (i.e., whether the bias in each group is similar or different) also is possible. This is of concern in intervention studies because [glossary term:] exposure to the intervention itself can create [glossary term:] differential error in reporting in the treatment group(s) relative to the control group.
  • To avoid the effects of these potential biases, an objective measure, such as measurement of serum carotenoids as a marker for fruit and vegetable intake, could be considered. Parallel changes in both the food record and [glossary term:] biomarker measures would give credence to the food record data. 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).

  • If your research objective is limited to assessing changes in mean intake of the study groups over time, a single n-day record at each relevant time may be sufficient. Furthermore, if, at baseline, assignment to the intervention and control groups is randomized, and if you are able to 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 non-consecutive n-day records are required.
  • If your research objective is to aid study participants in making and adhering to dietary changes as part of an intervention, periodic n-day food records with timely feedback may reinforce dietary change efforts.