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.
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
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:
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:
Dietary Data Web Tutorial
This tutorial walks you through the steps of conducting an analytical project from beginning to end, with examples of many common analytic procedures. Click here to open up a new window at the NCHS website.
When citing a WWEIA, NHANES data file, documentation, codebook, or frequencies:
U.S. Department of Agriculture, Agricultural Research Service, Beltsville Human Nutrition Research Center, Food Surveys Research Group (Beltsville, MD) and U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Health Statistics (Hyattsville, MD). What We Eat in America, NHANES YYYY-YYYY Type of File: Descriptive Name of File (FILENAME). (YYYY, Month). Available from: http://www.cdc.gov/remainder_of_url.xxx [accessed MM/DD/YY].
For data files, use the release month and year given with the associated codebook.
U.S. Department of Agriculture, Agricultural Research Service, Beltsville Human Nutrition Research Center, Food Surveys Research Group (Beltsville, MD) and U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Health Statistics (Hyattsville, MD). What We Eat in America, NHANES 2003-2004 Data: Dietary Interview - Total Nutrients Intakes -- First Day (DR1TOT_C). (2006, September). Available from: http://www.cdc.gov/nchs/about/major/nhanes/nhanes2003-2004/dr1tot_c.xpt [accessed 09/11/06].
When you use WWEIA, NHANES data in an analysis, please include among your keywords:
Frequently Asked Questions
What is What We Eat in America, NHANES, and when did it begin?
What We Eat in America (WWEIA), NHANES is a national food survey conducted as a partnership between the U.S. Department of Health and Human Services (DHHS) and the U.S. Department of Agriculture (USDA). WWEIA represents the integration of two nationwide surveys - USDA's Continuing Survey of Food Intakes by Individuals (CSFII) and HHS' NHANES. Under the integrated framework, DHHS is responsible for the sample design and data collection. USDA is responsible for the survey's dietary data collection methodology, development and maintenance of the food and nutrient databases used to code and process the data, and data review and processing. The two surveys were integrated in 2002.
How often are WWEIA, NHANES data released?
Data are released every two years as one dataset. The first WWEIA, NHANES data release was for 2001-2002. The most recent data release is 2009-2010.
How many days of dietary intake data per respondent are available in WWEIA, NHANES?
Beginning with the 2003-2004 data release, two days of dietary intake data are available per respondent. The 2001-2002 release includes one day of dietary intake data. Data collection for 2002 included a second dietary recall (Day 2). Because of confidentiality reasons concerning release of single-year data, dietary data for Day 2 were not publicly released.
What nutrients are included in the WWEIA, NHANES data?
How are the WWEIA data released?
WWEIA data are posted on the NHANES Examination File web pages for the respective survey year. There are two types of WWEIA data files, the Dietary Interview Individual Foods File and the Dietary Interview Total Nutrients File. The data are in SAS® transport format with a .xpt filename extension. Accompanying the data files are additional files containing codebooks, documentation, and frequencies.
Is it possible to combine WWEIA data from different release cycles?
Yes, the sample design for NHANES makes it possible to combine data cycles in order to increase the sample size and analytic options. However, in order to combine cycles appropriately, researchers must pay attention to variations between data cycles, including the following:
There are some individuals who have a record in the Total Nutrients File but no records in the Individual Foods File. Why?
A small number of WWEIA respondents ate no food on the survey day. They are referred to as "fasters." They can be identified by searching for records in the Total Nutrients File with the number of foods equal to zero. Fasters' intake records are considered to be complete, even though they did not report any foods or beverages. For all nutrients, they have a value of zero.