What is the 24-hour diet recall?

November 16, 2025 •

4 min read

According to the National Cancer Institute, the 24-hour dietary recall (24HR) is a common dietary assessment method in large population surveys. A 24-hour diet recall is a structured interview process that captures detailed data on all foods and beverages a person has consumed in the preceding 24 hours. This tool is instrumental in nutrition research, clinical settings, and public health surveillance to understand eating patterns and nutritional intake.

Quick Summary

The 24-hour diet recall is an interview-based method where a person reports their food and drink intake from the past day. The multiple-pass technique helps improve accuracy by prompting for forgotten details, portion sizes, and preparation methods. While effective for assessing short-term dietary habits, multiple recalls are needed to determine an individual's usual intake.

Key Points

Retrospective Method: The 24-hour diet recall is a retrospective interview used to gather details on all foods and beverages consumed over the past 24 hours.
Multiple-Pass Approach: A structured interview technique, like the Automated Multiple-Pass Method, is used to aid memory and gather complete, detailed information on food intake.
Trained Interviewers: Traditionally administered by trained interviewers, the process minimizes bias and accurately prompts for specific details on food, portion sizes, and preparation.
Low Respondent Burden: The interview typically takes a short time (20–60 minutes) and is less burdensome than multi-day food records, which helps achieve higher response rates.
Technology Integration: Automated, web-based tools are now used to standardize the recall process, include image-assisted portion estimations, and reduce costs.
Assesses Population Intake: A single 24-hour recall is effective for estimating the average intake of a population but not for an individual's long-term habits.
Requires Multiple Recalls for Usual Intake: To understand an individual's usual diet, multiple recalls on non-consecutive days are required to account for day-to-day variation.
Prone to Recall and Reporting Bias: Like other self-report methods, it is subject to recall bias, where individuals may forget items, and social desirability bias, where they underreport 'bad' foods.

The 24-hour diet recall (24HR) is a method used by dietitians, researchers, and other health professionals to gather precise and quantitative information about an individual's eating habits. It is a retrospective tool, meaning it relies on a person's memory of their food and beverage consumption from the previous day. This method stands in contrast to prospective methods, like food records, where intake is documented as it occurs. The success of a 24HR largely depends on the respondent's memory and the interviewer's skill in probing for detailed information.

How the 24-hour diet recall works

To maximize the accuracy and completeness of the data collected, most 24HRs follow a standardized multi-pass approach. This systematic process helps respondents remember everything they consumed, from main meals to forgotten snacks and condiments. The interview is typically conducted by a trained professional, either in-person, over the phone, or via automated online tools.

The multi-pass method in detail

The Quick List: The interviewer asks the respondent to provide a rapid, uninterrupted list of all foods and drinks consumed over the past 24 hours. This captures the main eating occasions and items without dwelling on details.
The Forgotten Foods Pass: The interviewer uses specific prompts to remind the respondent of items that are commonly forgotten. These might include snacks between meals, sauces, beverages, or additions like butter on toast.
The Time and Occasion Pass: The interviewer reviews the list chronologically to help the respondent recall the time and occasion of each food item (e.g., breakfast, mid-morning snack, lunch).
The Detail Cycle Pass: This is the most in-depth stage. For every food item, the interviewer asks for specific details, such as portion size (often using visual aids like food models or photographs), brand names, preparation methods (e.g., fried, baked, boiled), and any condiments used.
The Final Probe: The interviewer conducts a final review of the entire 24-hour period to ensure nothing was missed. This serves as a last-chance check for any forgotten items or details.

Benefits and limitations of the method

While the 24HR is a powerful tool, it has distinct advantages and disadvantages that influence its suitability for various applications. It is particularly useful for assessing population-level dietary intake but requires repeated measurements for reliable individual assessment.


Feature	24-Hour Diet Recall	Food Record / Diary
Reliance on memory	Relies on the respondent's memory of the previous day's intake, which can lead to inaccuracies.	Does not rely on memory, as intake is recorded in real-time.
Respondent burden	Low, as the interview is relatively short (20–60 minutes).	High, requiring continuous recording and portion size estimation, potentially altering eating habits.
Assessment period	Retrospective, focusing on a single, short-term 24-hour period.	Prospective, capturing intake over multiple days.
Alteration of diet	Low risk of altering eating habits, especially if the respondent is unaware of the recall in advance.	High risk of reactivity bias, where participants consciously or unconsciously change their diet because they know it is being recorded.
Data quality	High level of detail captured through trained interviewers and structured questioning, including portion sizes, preparation, and specific ingredients.	Dependent on the participant's diligence and ability to accurately weigh or estimate portions in real-time.
Cost	Can be expensive due to the need for trained interviewers and data coders, though automated tools reduce this.	Lower cost for large studies, but can still require significant data processing.

Analysis of 24HR data

Once the interview is complete, the collected data is converted into specific nutrient information using food composition databases. Computer-based programs are often used to automate this process, converting reported portion sizes into gram amounts and matching them with nutrient data. Researchers and dietitians can then calculate the intake of energy, macronutrients, and micronutrients. This information is valuable for national health surveys, evaluating nutritional interventions, and counseling individuals.

The use of repeated recalls

While a single 24HR is useful for assessing the average intake of a population, it does not provide a reliable measure of an individual's usual dietary intake due to day-to-day variations. For individual-level assessment, multiple recalls conducted on non-consecutive days, and preferably covering both weekdays and weekends, are necessary. This practice helps account for the natural fluctuations in a person's diet and provides a more robust picture of their eating patterns. The National Cancer Institute has developed statistical methods, like the NCI method, to estimate usual dietary intake distributions from repeated 24HR data.

The role of technology in modern 24HRs

Technology has significantly advanced the 24HR method. Automated self-administered online tools, such as the Automated Self-Administered 24-Hour Dietary Assessment Tool (ASA24) and Intake24, have standardized the recall process and reduced the reliance on trained interviewers. These systems often feature image-assisted portion size estimation, making it easier for users to accurately report their food quantities. This shift has helped decrease costs, reduce researcher burden, and expand the reach of dietary surveillance.

Conclusion

The 24-hour diet recall is a fundamental and widely-used method in nutritional science for assessing dietary intake over a short period. Its strengths lie in its ability to provide highly detailed, quantitative data with relatively low respondent burden. By using structured, multiple-pass interviews and increasingly sophisticated technological tools, researchers and clinicians can minimize recall bias and improve the accuracy of portion size estimates. However, it is crucial to recognize its limitations, particularly that a single recall is insufficient for individual-level assessment of usual intake. When multiple recalls are collected and analyzed appropriately, the 24HR provides invaluable insights into eating behaviors and nutritional adequacy for both individuals and entire populations. For more details on the automated multiple-pass method used in U.S. national surveys, visit the USDA website.

Frequently Asked Questions

A trained professional, such as a registered dietitian, nutritionist, or researcher, typically conducts the 24-hour diet recall. Increasingly, automated online tools are also used for self-administration.

The recall is conducted as a structured interview, often using a multi-pass method to guide the person through their previous day's food and beverage consumption. This includes prompts for forgotten items, detailed descriptions, and portion size estimation.

No, a single 24-hour recall is not representative of a person's usual dietary intake due to natural day-to-day variations. Multiple recalls over non-consecutive days are needed to get a more accurate picture of habitual eating patterns, especially for individual nutritional counseling.

A 24-hour recall is a retrospective interview reliant on memory, while a food record (or diary) is a prospective method where the participant records their intake as they eat it. Food records require more participant effort but do not rely on memory.

Limitations include reliance on memory, potential for recall and social desirability bias (underreporting 'bad' foods), and the intensive resource requirements for trained staff and data analysis.

Interviewers use visual aids such as food models, photographs, or measuring cups to help the respondent provide accurate portion size estimates. Automated online tools also often use images to assist with this process.

The multi-pass method is designed to improve memory recall and reduce omissions. The staged approach, from a quick list to detailed probes, helps respondents remember foods and drinks that they might otherwise forget.