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An Integrated Federal Food Survey
What We Eat in America (WWEIA) is the dietary intake interview component of the National Health and Nutrition Examination Survey (NHANES). WWEIA is conducted as a partnership between the U.S. Department of Agriculture (USDA) and the U.S. Department of Health and Human Services (DHHS). DHHS is responsible for the sample design and data collection, and USDA is responsible for the survey’s dietary data collection methodology, maintenance of the databases used to code and process the data, and data review and processing. USDA also funds the collection and processing of Day 2 dietary intake data, which are used to develop variance estimates and calculate usual nutrient intakes.
Data Collection Two days of 24-hour dietary recall data are collected in WWEIA, NHANES. The Day 1 interview is conducted in person in the Mobile Examination Center (MEC). After completion of the in-person interview, an appointment is set for the Day 2 interview. The Day 2 interview is collected by telephone 3 to 10 days following the MEC interview, but not on the same day of the week as the MEC interview.
WWEIA data are collected using USDA’s dietary data collection instrument, the Automated Multiple-Pass Method (AMPM). The AMPM is a fully computerized method for collecting 24-hour dietary recalls either in person or by telephone. In this multiple-pass method, information is collected by 5 standardized steps. The AMPM is a research-based approach designed to enhance efficient collection of complete and accurate food intake data in large-scale national surveys and reduce respondent burden. The AMPM is updated yearly to reflect the changing food supply. Read more about the AMPM.
At the MEC dietary interview, a set of three-dimensional food models are available for the participant to use when reporting amounts of foods. After the Day 1 interview, participants are given USDA’s Food Model Booklet and a limited number of three-dimensional models (measuring cups and spoons, a ruler, and two household spoons) to be used for estimating food amounts during the telephone interview. The Food Model Booklet includes two-dimensional drawings of various sizes of glasses, mugs, bowls, mounds, circles, and other measures.
Information Collected During Interview
| For each food and beverage consumed during previous 24-hour period |
Detailed description |
| Additions to the food |
| Amount consumed |
| What foods were eaten in combination |
| Time eating occasion began |
| Name of eating occasion |
| Food source (where obtained) |
| Whether food was eaten at home |
| Amounts of food energy and 60+ nutrients/food components provided by the amount of food (calculated) |
| For each respondent on each day |
Day of the week |
Amount and type of water consumed, including total plain water, tap water, and plain carbonated water
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| Source of tap water |
| Daily intake usual, much more or much less than usual |
| Use and type of salt at table and in preparation |
| Whether on a special diet and type of diet |
| Frequency of fish and shellfish consumption |
| Daily total intakes of food energy and 60+ nutrients/food components (calculated) |
Data Processing
USDA's Food and Nutrient Database for Dietary Studies (FNDDS) is used for processing the WWEIA dietary intakes. The FNDDS includes comprehensive information that can be used to code individual foods and portion sizes reported by WWEIA participants and also includes nutrient values for calculating nutrient intakes. FNDDS values are updated for every 2-year WWEIA, NHANES release cycle. The FNDDS is available for free download from the USDA's Food Surveys Research Group (FSRG) website. It can be used to enhance analysis of the WWEIA dietary intake data, as well as in coding and analyzing data collected in other studies. Read more about the FNDDS.
WWEIA/NHANES Data Release
Data are released at 2-year intervals. All NHANES files are available for free download from the NHANES website.
All data files are in SAS® transport format (.xpt) and can be used with any package that supports that file format. For general information on downloading the data, consult the frequently asked questions page for the data cycle in question.
Each data release file is accompanied by three additional components:
- Documentation - Includes information about data collection, quality control, data processing, and analytical procedures.
- Codebook - Includes names assigned to each data item, question text, response categories, valid values, and other information.
- Frequencies - Includes raw frequency counts for all variables in the data file.
To receive an e-mail notice from FSRG when new WWEIA data are released, you may join the FSRG listserv.
Dietary Intake Data Files
For each 2-year data release cycle, the following dietary intake data files are available:
- Individual Foods File - Contains one record per food for each survey participant. Foods are identified by USDA food codes. Each record contains information about when and where the food was consumed, whether the food was eaten in combination with other foods, amount eaten, and amounts of nutrients provided by the food. Starting with the data years 2003-2004, the source of each food is provided.
- Total Nutrient Intakes File - Contains one record per day for each survey participant. Each record contains daily totals of food energy and nutrient intakes, daily intake of water, intake day of week, total number foods reported, and whether intake was usual, much more than usual or much less than usual. The Day 1 file also includes salt use in cooking and at the table; whether on a diet to lose weight or for other health-related reason and type of diet; and frequency of fish and shellfish consumption (for selected groups).
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