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  1. Science & Research (Food)

Total Diet Study

CFSAN/Office of Analytics and Outreach

The FDA Total Diet Study (TDS) monitors levels of nutrients (e.g., calcium and iron) and contaminants (e.g., cadmium and lead) in foods commonly eaten by people in the U.S. The TDS complements FDA’s other food safety and nutrition programs. 

The TDS program began in 1961 to monitor for radioactive contamination of foods. Over the years, the TDS expanded to monitor levels of nutrient elements, toxic elements, pesticide residues, and other chemicals in food. The ongoing nature of the TDS enables us to track trends in the average U.S. diet. 

TDS Modernization

Beginning in 2013 through 2018, the FDA worked to modernize the TDS program by updating the sampling plan, the foods sampled (the food list), and our analytical methods. These improvements will help the FDA continue our decades long effort to study and better understand Americans’ dietary exposure to toxic and nutritional elements, pesticides, industrial chemicals, and radionuclides.

The updated sampling plan, implemented in 2018, increases the quality and utility of TDS data and allows us to determine whether nutrients and contaminants in foods vary depending on where or when the food is purchased. The new sampling plan is based on population distributions in all 50 states; all areas are included in the sampling plan, but densely populated areas are more likely to be included as sampling sites. This is an improvement on the previous plan, which did not consider population distributions, and was based on the contiguous 48 states. 

The new sampling plan includes two types of sample collections, one for foods that are distributed nationally, and one for foods with analyte concentrations that may vary regionally and seasonally, such as fresh produce, meats, and dairy products. Foods with nutrient or contaminant concentrations that are less likely to vary by location or by time of year are categorized as “national” foods. Foods with nutrient or contaminant concentrations that may vary by location or by time of year are categorized as “regional” foods. 

The updated food list was based on an extensive analysis of the latest data available from What We Eat in America (WWEIA), the food consumption portion of the National Health and Nutrition Examination Survey (NHANES). WWEIA was analyzed to identify foods with the highest per capita consumption and to select highly consumed foods from each major food group (e.g., fruits, vegetables, meat/poultry/fish, dairy). A complete cycle of the FDA TDS includes 2 national and 24 regional collections and takes place over a 2-year period (see figure below showing an example sampling plan for a 1-year collection period). 

Sampling Plan by Calendar Year Graph

The above figure shows a 1-year collection period, where the regional collections are randomly selected such that samples are collected in each region twice a year. The national foods are collected from a single location near the Kansas City Laboratory (KCL), whereas the regional foods are collected in six regions (see map below). The modernized TDS program also utilizes advancements in analytical chemistry and dietary exposure methodology.   

Regional Sampling Plan Graph

How to Use This Site

Results of the TDS, from 1991 to 2017, are available to the public in electronic form on this website. Results prior to 1991 may be found in the publications listed on the publications page of this website. Each section of the website explains a different aspect of the study, from a description of how the study was designed prior to 2018 to an explanation of how the results are organized, including a link to zipped text files of the data. 

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Note: TDS samples collected under the modernized program (beginning in 2018) have been analyzed and will be posted soon, along with further explanation of the modernized TDS program.

If you have questions about the Total Diet Study, email TDS@fda.hhs.gov.

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