Dietary Assessment Primer

24-hour Dietary Recall (24HR) At a Glance


To obtain detailed information about all foods and beverages consumed on a given day.


A 24-hour dietary recall (24HR) is a structured interview intended to capture detailed information about all foods and beverages (and possibly, [glossary term:] dietary supplements) consumed by the respondent in the past 24 hours, most commonly, from midnight to midnight the previous day. A key feature of the 24HR is that, when appropriate, the respondent is asked for more detailed information than first reported. For example, a respondent reporting chicken for dinner or a sandwich for lunch would be asked about the preparation method and type of bread. This open-ended response structure is designed to prompt respondents to provide a comprehensive and detailed report of all foods and beverages consumed.

In addition to other detailed descriptors, such as time of day and source of food, portion size of each food and beverage is captured. Food models, pictures, and other visual aids may be used to help respondents judge and report portion size and may improve [glossary term:] accuracy.

Dietary recalls typically ask about foods and beverages first, before questions on dietary supplements.

A 24HR usually requires 20 to 60 minutes to complete.

Standardized automated interviewing systems that include multiple passes, such as the USDA's Automated Multiple-Pass Method, and the University of Minnesota's Nutrition Data System for ResearchExternal Web Site Policy, have been developed to facilitate complete recalls. These systems include nearly complete automated coding that is supplemented by manual coding for reported foods or beverages not in the database.

24HRs are typically administered by a trained interviewer, but automated self-administered tools, such as the National Cancer Institute's Automated Self-Administered 24-Hour Dietary Assessment Tool (ASA24), also are available.

Utility of Data

Limitations of Data

  • The requirements of completing a 24HR may limit participation in some groups, leading to potential [glossary term:] selection bias.
  • Because a single administration of a 24HR is unable to account for [glossary term:] day-to-day variation, two or more non-consecutive recalls are required to estimate usual dietary intake distributions. Multiple administrations are also recommended when 24HRs are used to examine diet and health or other variables.

Salient Features Compared to Other Self-Report Instruments Methods

For an at-a-glance comparison of the major features of self-report instruments for assessing diet, including the 24HR, see the Comparing Dietary Assessment Instruments table.