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CFSAN/Office of Plant and Dairy Foods and Beverages
April 2001; Updated June 2003
The TDS involves purchasing samples of food throughout the U.S., preparing the foods as they would be consumed (table-ready), and analyzing the foods to measure the levels of the analytes of interest. Food samples are purchased by FDA personnel from supermarkets or grocery stores in selected cities, and the samples are sent to FDA laboratories for analysis. Dietary intakes of these analytes are then estimated for the U.S. population by multiplying the levels found in the TDS samples by the amounts of foods consumed based on surveys conducted by the U.S. Department of Agriculture (USDA). The overall strategy and goals of the TDS have remained constant since its inception in 1961, but the specific methodology has been revised periodically. Exhaustive histories of the TDS have been published elsewhere (See the list of references.).
The number and type of foods collected and analyzed in the study are updated from time to time to reflect changing eating patterns in the U.S. The number of different foods sampled in the TDS has increased from 82 food items when the study was initiated to about 280 foods in the current program. Major revisions of the food list were implemented in 1982 and early 1991. Later in 1991, in response to the Food Quality Protection Act, additional infant and toddler foods were added to the TDS to provide more information on levels of pesticides and lead in the diets of young children. The most recent revision of the food list was completed in 2003; the new list of foods will be posted on this website when the analytical results become available.
Besides changes in the number and types of foods purchased in the TDS, the way in which the foods are analyzed has also changed over time. In some of the earlier studies, similar foods were combined before analysis to form composites representing major commodity groups (e.g., dairy, meat, grains). Beginning in the early 1980s, TDS foods were analyzed individually; this approach is still used in the TDS today.
Since 1982, sample collections (also referred to as market baskets (MB) have generally been conducted four times each year, once in each of four geographic regions of the country (West, North Central, South, and Northeast). For each of the four collections, samples of each food are purchased in three cities in the region and are shipped to a central FDA laboratory. The foods are prepared as they would be consumed (table-ready), and the three samples are combined to form a single analytical composite for each TDS food. Current TDS analytes include pesticide resides, industrial chemicals, elements, and folate.
Numerous units within FDA participate in the operation of TDS. The Center for Food Safety and Applied Nutrition, College Park, MD, provides overall management of the program and summary of the laboratory results. FDA District Offices from across the U.S., within the Office of Regional Operations, collect the foods and ship them to the Kansas City District Laboratory, Lenexa, KS, where the foods are prepared and analyzed for pesticide residues and elements. Portions of the composites are sent to FDA's Winchester Engineering and Analytical Center, Winchester, MA, for analysis of radionuclides and to FDA's Atlanta Center for Nutrient Analyses, Atlanta, GA for folate analysis.
The foods collected in the TDS (TDS food list) represent the major components of the diet in the US population. The food list is based on results of national food consumption surveys and is updated from time to time to reflect changes in food consumption patterns. The foods collected from 1990 through 2002 [market baskets (MB) 91-3 through 02-4] were based on consumption data reported in USDA’s 1987-88 Nationwide Food Consumption Survey (1987-88 NFCS) (USDA 1990, Pennington 1992). The food list was most recently updated in 2003, based on data from USDA’s 1994-96, 1998 Continuing Survey of Food Intakes by Individuals (1994-96, 1998 CSFII) (USDA 2000), and will be reflected in the TDS analytical results beginning with MB 03-1.
Dietary exposure to TDS analytes can be estimated by multiplying the levels of the analytes found in the TDS food by the amount consumed of that food. The food consumption amounts are compiled for the total US population and 14 age/sex subgroups, and are collectively referred to as the TDS diets.
The TDS diets are derived from the national food consumption survey data and are generally compiled in conjunction with updates of the TDS food list. During the food consumption surveys, detailed information is collected on the types and amounts of foods consumed. In all, over 5,000 different foods were reported in the each of the surveys upon which the TDS food lists and diets are based (1987-88 NFCS and 1994-96, 1998 CSFII).
Although there are many fewer TDS foods (~280) than survey foods (> 5,000), the TDS diets attempt to account for consumption of all foods. To accomplish this, the survey foods were grouped (or mapped) according to their similarity to TDS foods. A spreadsheet is available as a compressed, tab-delimited text file* showing the mapping of TDS foods to 1994-98 CSFII food codes. Next, average per-capita (eaters and non-eaters) daily consumption amounts were calculated for each survey food and the consumption amounts of all survey foods in each group were subtotaled to derive a consumption amount for each TDS food. This approach assumes that the analytical profile of the survey foods are similar to that of the TDS foods to which they are assigned, and that the TDS diets could provide an estimate of total exposure to the analytes from all foods in the diet, not just from the TDS food alone.
This process was repeated for consumption estimates for the total US population as well as the following 14 age/sex subgroups:
| 6-11 month infants 2-year old children 6-year old children 10-year old children |
14-16 year females 14-16 year males 25-30 year females 25-30 year males |
40-45 year females 40-45 year males 60-65 year females 60-65 year males |
70+ year females 70+ year males |
All TDS samples collected and analyzed between 1991 and 2002 are based on the food list compiled in 1990 (Pennington 1992). The food list was last updated in 2003; this is the basis for all samples collected and analyzed from 2003 to the present.
The TDS food list and diets compiled in 1990 were based on data from the 1987-88 NFCS. A second version of the TDS diets for the 1990 food list was compiled from data from the 1994-98, 1998 CSFII so that TDS analytical results could be linked to more recent food consumption data. A third version of the TDS diets, compiled for the 2003 TDS food list, was also based on the 1994-98, 1998 CSFII.
Following are links to each version of the diets. Each file is a self-extracting compressed (zipped), tab-delimited text file* that can be downloaded, decompressed (double-click the file or use a program like Stuffit Expander), and imported by database or spreadsheet software. For best viewing and data manipulation, the text files should be saved and then opened from a database or spreadsheet program such as Microsoft Excel, Corel QuattroPro and Lotus 1-2-3.:
