NHANES III Dietary Interview Component Dietary interviews were administered to all examinees by a trained dietary interviewer in the mobile examination center (MEC). Respondents reported all foods and beverages consumed except plain drinking water (i.e., not bottled) for the previous 24-hour time period (midnight to midnight). An automated, microcomputer-based dietary interview and coding system known as the NHANES III Dietary Data Collection (DDC) System was used to collect all NHANES III dietary recall data. The DDC system was developed for use in the survey by the University of Minnesota's Nutrition Coordinating Center (NCC). The dietary interviews were conducted in English and Spanish by bilingual dietary interviewers in a private room to ensure confidentiality. Proxy respondents were permitted for infants and children aged two months through five years and for other respondents who were unable to report on their own. Children aged six to 11 years were permitted to report their own intake if the interviewer deemed it acceptable and appropriate, but many interviewers for respondents in this age category were completed by proxy or with the child and a proxy. The dietary interviewers contacted other information sources such as care providers and schools to obtain complete dietary intake data for respondents. The primary source of food composition data for NHANES III is the U.S. Department of Agriculture (USDA) Survey Nutrient Database; two nutrient files were provided by USDA for use in NHANES III (USDA 1993, 1995). Each USDA file contained food composition values that were appropriate for the time period during which the NHANES III data were collected. Additionally, food composition data for a small number of herbs and spices were obtained from NCC (NCC, 1996). The DDC system's foods database was designed specifically to handle time-related changes in food descriptions, food amounts, and recipes; updated information was applied retrospectively to data collected in the early part of NHANES III. As was mentioned earlier, two USDA food composition databases were used to assign nutrient values to the NHANES III dietary recalls (USDA 1993; USDA, 1995). In addition to data changes that occurred in the nutrient values of foods due to food product reformulations, recipe changes, and so forth, the U.S. marketplace underwent tremendous growth and change as new food product lines were introduced and new food components were added to the food supply (e.g., fat substitutes and artificial sweeteners). The impact of these and other changes may require additional analysis. Dietary recall interviews were edited by the interviewers to ensure that they were as complete as possible. NCHS completed all final editing and determinations regarding the completeness and reliability of the dietary recalls. Analysts should note that the data reported are self-reported data. Extreme values were verified. Information pertaining to the use of nutritional supplements and antacids was reported separately during the Household Adult and Household Youth Interviews. A number of quality-control monitoring techniques were employed during the survey. The techniques for monitoring the Dietary Interview component included observations of actual dietary interviews and reviews of audiotape interviews by NCHS and contractor staff. In addition, the dietary interviewers worked in two-person teams; there was one team in each MEC. The dietary interviewers performed 10-percent cross-check reviews of their partners' work using printed recall reports. Finally, newsletters, field memoranda, telephone calls, and staff retraining sessions were other methods used to maintain quality control during the survey. Refer to the NHANES III Dietary Interviewer's Training Manual for the dietary interview protocol (U.S. DHHS, 1996b). Analysts are encouraged to use six years of survey data in their analyses. The reliability of estimates is improved when larger sample sizes are used. For more detailed information, see the Analytic and Reporting Guidelines for NHANES III (U.S. DHHS, 1996b). In addition, MEC final examination weights (WTPFEX6) should be used when analyzing the total nutrient intake data and related questionnaire data in this file. For more information on the use of sample weights in NHANES III data analysis, refer to the NHANES III Analytic and Reporting Guidelines (U.S. DHHS, 1996b). NHANES III Total Nutrient Intakes and Foods Data Files NCHS prepared 4 datasets that are based on the 24-hr dietary recall interview. Total nutrient intakes were reported in the NHANES III Examination Data file (Catalog 76200). Three foods files were prepared; three files are found in Catalog 76700: NHANES III Individual Foods Data File from the Dietary Recall; NHANES III Combination Foods Data File from the Dietary Recall; NHANES III (Variable) Ingredients Data File from the Dietary Recall. Documentation was prepared for each of the foods data files. Data users are encouraged to review all of the documentation prior to using the data files. Look-up Tables for the NHANES III Foods Data Files Textual descriptions for several NHANES III Foods Data File numeric code variables are located in an Appendix section that accompanies the Foods Data Files. The Appendix files are referred to as "look-up" tables throughout the data file documentation for the Foods Data Files. Computer code is provided so that data users can merge the foods data files with the information in the Appendix/look-up tables. COMBINATION FOODS FILE Multi-component combination foods are foods that are comprised of more than one component food. Any food in the NHANES III Individual Foods File that is comprised of more than one component food is considered to be a multi-component combination food. Approximately 85,000 multi-component foods were reported during NHANES III. Fifteen combination food type codes (DRPTCC) were developed for use in NHANES III; the dietary interviewers assigned codes to all multi- component combination foods reported during NHANES III. Some examples of combination type codes include beverage combinations (DRPTCC=7), sandwich combinations (DRPTCC=1), mixed dish combinations (DRPTCC=4) and salad combinations (DRPTCC=3). A cheese sandwich entered by its components: bread, cheese, mustard, and lettuce would have a DRPTCC=1. In addition to the multi-component type of combination foods, there were single component combination foods reported during the survey. Single component combination foods were entered into the DDC System using generic or brand name product food entry selections in the DDC system. If a respondent ate a sandwich or mixed dish in a restaurant and could not provide any details about the food, the DDC System's generic combination food selections were used. A cheese sandwich or beef taco could be entered as such using the appropriate selections in the DDC system; generic combination food options were available for many combination foods. A second example would be for a sandwich eaten in a "fast food restaurant:; if the restaurant was one of the commercial establishments in the DDC System, the interviewers could select the restaurant menu item directly as long as the respondent ate the sandwich as prepared. The NHANES III Individual Foods File lists the food records and component food records for single and multi-component combination foods. Multi-component combination foods have a Combination Food Flag (DRPCFF) value equal to 1. Single component combination foods have DRPCFF=0. Some multi-component foods are comprised of a single component combination food plus additional food components and have a DRPCFF=1 because the food is a multi-component food. The CFF provides a single, summary data record for multi-component combination foods reported in the survey; descriptive information and nutrient values for multi-component combination foods are included in the CFF records. The CFF was produced by combining component food data in the Individual Foods File into a single combination food record. In the sandwich combination example described earlier, the CFF data for the "sandwich" were derived by summing food gram weights and nutrient values for the bread, cheese, mustard, and lettuce components of the sandwich. A single food record for the "cheese sandwich" would appear in the CFF for this combination food. Food energy and nutrient values for CFF records have distinctive variable names to distinguish them from IFF food energy and nutrient variables. Two criteria were required for inclusion in the CFF. First, the final dietary recall status code (DRPSTAT) for the dietary recall had to be equal to 1, 2, or 5. Second, a multi-component food had to have been reported during the dietary interview. Only the foods that were multi-component foods in the Individual Foods File are included in the CFF. Some NHANES III examinees do not have any records in the CFF because their recall did not include multi-component foods. The single component combination foods have single component record foods in the Individual Foods File; the Combination Food Flag (DRPCFF) value for single component combination foods is equal to zero. When respondents were unable to describe the components of a combination food such as a sandwich, the DDC System's generic food entries were selected during the dietary interview. Many brand name combination foods are single component combination foods. When the generic and brand name combination food entries were selected, a standard foods database recipe was used to assign the food code and nutrient values to the combination food. Single component generic and brand name combination foods were not included in the CFF unless component foods were added to or were omitted from the base food. For example, if a respondent added avocado slices to a base food item such as a "fast food restaurant" sandwich, the resulting food was a combination food that consisted of avocado and the restaurant sandwich. If major sandwich components (salad dressing, cheese, etc.) were removed or omitted from a "fast food restaurant" sandwich, the component foods that were eaten were entered individually into the DDC System, thus creating a multi-component combination food. The Individual Foods File and CFF data may be combined to identify all reports of specific combination foods. The DRPFCODE in the Individual Foods File, and the DRPCCODE in the CFF can be used to accomplish this. The CFF data include food gram weights, nutrient data, and descriptive information about the combination foods. A combination food code (DRPCCODE) was assigned to many combination foods. The DRPCCODE was either a USDA food code or a special food code that was developed by NCHS. NCHS created a small number of special food codes because many combination foods reported during NHANES III could not be coded with existing USDA food codes. For example, there were numerous reports of tortilla combinations containing eggs and meat. NCHS also added a small number of food codes for unusual food combinations. All combination food codes (DRPCCODE) are linked to food code descriptions. The look-up table called "Codebook" can be used to obtain text descriptions for DRPCCODE. Seven of the fifteen combination food types (DRPTCC) were assigned combination food codes (DRPCCODE): sandwiches; mixed dishes; mixed dishes with additions; meat, fish, and poultry with additions; soups and stews; other foods eaten together; and tortilla combinations. The DRPCCODE was assigned by NCHS to provide a means of describing the combination foods reported during NHANES III. Many of the combination foods reported during the survey were difficult to code due to the fact that unusual combinations were reported, equal amounts of multiple components were reported as components of a combination food, and numerous variations of foods were reported. Eight combination food types have generic combination foods descriptions that are based on their combination food type label (DRPTCC). Beverage combinations, cereal with additions, vegetables with additions, desserts, vegetable combinations, bread with additions, frozen meals, and salads have generic combination type descriptions that are associated with DRPTCC. Many of the combination foods reported in these categories were comprised of equal amounts of component foods. Second, there were no USDA food codes for many of these combination foods. For example, ready-to-eat breakfast cereals eaten with sugar and fresh fruit, or unusual vegetable combinations, for example, do not have USDA food codes. Additionally, many combination foods were foods eaten in combination with other foods instead of being components of a single "food" such as a sandwich, taco or stew. It is suggested that analysts check the Individual Foods File first to review the frequency of occurrence of single component and multi-component combination foods. The food code, brand name, and food identification codes (DRPFCODE, DRPCOMM, and DRPFID) variables are useful to describe single component combination foods as well as specific components of multi-component combination foods. A particular component food may appear in several combination type codes. The CFF combination type code (DRPTCC) and combination food code (DRPCCODE) variables are useful for planning analyses involving multi-component combination foods. Detailed documentation is provided to describe the DRPCCODEs. Notes to Analysts There are two exceptions to the basic combination foods coding procedures described earlier. The approach NCHS used to handle these data entry exceptions is described. Exception #1: There are single component foods in the CFF that were prepared with more than one type of ingredient. In such cases, the only way to capture specific ingredient information reported by the respondent using the DDC System was to enter the food as a multi- component or combination food. One example was homemade cookies prepared with equal amounts of butter and margarine. The dietary interviewers were instructed to enter half of the total amount of cookies eaten using margarine as an ingredient (component 1) and half of the amount eaten using butter as an ingredient (component 2). To describe this particular "combination," the combination type code (DRPTCC) "Other foods eaten together" was used. Exception #2- Modified Recipe Foods: The second example of single component foods appearing as combination foods were those with modified recipes -- e.g., homemade cornbread prepared without fat. To report this modified cornbread, NCHS and NCC developed a fat-free cornbread recipe. The ingredients were entered into the DDC System as separate food components resulting in a "combination food" as follows: corn meal (component 1), egg (component 2), milk (component 3), and so forth. Modified recipe foods were coded using DRPTCC=8 or "other foods eaten together". In summary, combination foods were reported either as single component foods or multi-component foods in the Individual Foods File. The CFF provides a single record summary of the multi- component foods reported in the survey. The CFF provides total gram weight and nutrient data for many combination foods reported during the survey. The CFF is sorted by case number (CASE), meal number (DRPMN), and food number(DRPFN).