The nutrient and food group database, created for analyzing the DHQ II, is based on a compilation of national 24-hour dietary recall data from the National Health and Nutrition Examination Surveys (NHANES) conducted in 2001-02, 2003-04, and 2005-06. These 24-hour dietary recall data were used to determine foods to include and portion size units on the DHQ II.
The NHANES foods reported on 24-hour dietary recalls were placed into cognitively and nutritionally similar food groups and analyzed for their contribution to nutrient intakes to determine the list of foods to include. Those food groups selected for inclusion in DHQ II include many different individual foods recorded on recalls that are subsumed by the line item, for example, "lasagna, stuffed shells, stuffed manicotti, ravioli, or tortellini." The NHANES data were analyzed to provide a mean nutrient or food group value, by gender and portion size, based on all reported intakes of the various lasagna, stuffed shells, etc., reported on 24-hour recalls in NHANES. This produced a single nutrient or food group value by portion size and gender for each food on the DHQ II. The primary databases used to compute nutrient and food group estimates are the U.S. Department of Agriculture's (USDA) Food and Nutrient Database for Dietary Studies (FNDDS) and USDA's MyPyramid Equivalents Database. Additional nutrients have been added from the Nutrition Data System for Research (NDS-R) (see below).
Nutrient values were not computed separately by age group because our research (cited below) showed that separate nutrient values by age group did not improve estimates. However, for investigators interested in adding age-specific values in the database, the Diet*Calc software has the flexibility to allow you to do so. For a more detailed description of the method used to create the values for the DHQ II database, please see:
Subar AF, Midthune D, Kulldorff M, Brown CC, Thompson FE, Kipnis V, Schatzkin A. Evaluation of alternative approaches to assign nutrient values to food groups in food frequency questionnaires. Am J Epidemiol. 2000 Aug 1;152(3):279-86.
Nutrients from Nutrition Data System for Research (NDS-R)
The methods used to add NDS-R nutrients to the DHQ II database are the result of the efforts of Dr. Lori Beth Dixon at Syracuse University and Thea Zimmerman at Westat. In the DHQ II database such nutrients are clearly marked in the variable labels as "(NDS-R based)". The methods used to add NDS-R nutrients to the DHQ database are described in:
Dixon LB, Zimmerman TP, Kahle LL, Subar AF. Adding carotenoids to the NCI Diet History Questionnaire Database. J Food Comp Anal2003;16:269-80.
To summarize, however, these values are the result of matching NHANES food codes to similar foods in the nutrient database of the Nutrition Data Systems for Research (NDS-R) from the University of Minnesota, which has nutrient values not available from NHANES. The values for the DHQ were then computed using the data based approach described in:
Subar AF, Midthune D, Kulldorff M, Brown CC, Thompson FE, Kipnis V, Schatzkin A. Evaluation of alternative approaches to assign nutrient values to food groups in food frequency questionnaires. Am J Epidemiol 2000 Aug 1;152(3):279-86.
Development of the C-DHQ II Nutrient Database
The C-DHQ II nutrient database was created from the Canadian Community Health Survey (CCHS), Cycle 2.2, Nutrition (2004) 24-hour dietary recall data. CCHS data collection was completed using the Automated Multiple-Pass Method (AMPM), developed by the U.S. Department of Agriculture (USDA) and adapted by Health Canada to account for differences in foods available to Canadian consumers, the ethnic diversity of Canadian diets and differences in food preparation.
CCHS reported foods were grouped into categories of similar foods and analyzed to determine their contribution to the overall Canadian diet and for inclusion in the food list. Each C-DHQ II question is linked to gender- and portion-size specific nutrient profiles generated from the CCHS nutrient database comprised of 33 nutrients. Data analysis for the development of the C-DHQ II nutrient database was provided by Geraldine Lo Siou (Alberta Health Services-Cancer Control) and Didier Garriguet (Statistics Canada). Plans are underway to supplement the list of nutrients from other sources (e.g., the Canadian Nutrient File (CNF) Version 2010, and the Food and Nutrient Database for Dietary Studies (FNDDS)).