USE OF NHANES DATA TO ASSIGN NUTRIENT DENSITIES TO FOOD GROUPS IN A MULTIETHNIC DIET HISTORY QUESTIONNAIRE

In epidemiological studies of diet and chronic disease, a brief yet co mprehensive diet history questionnaire must aggregate some foods into food groups. A nutrient density is assigned to each food group by aver aging the densities of its constituent foods. A person's intake of a g iven nutrient is then estimated by multiplying the reported consumptio n of each food group by its average nutrient density and summing over food groups. These calculations could introduce bias in multiethnic st udies, if the average nutrient densities assigned to food groups are i nappropriate for some ethnic populations. This issue is examined here for intakes of total fat, saturated fat, and vitamin A for U.S. blacks and whites. We used 24-hour diet recall data from the Second National Health and Nutrition Examination Survey (NHANES II) to assess black-w hite differences in relative frequency of consumption of foods within food groups of a diet history questionnaire. We also calculated ethnic -specific average nutrient densities for each food group by weighting the densities of its foods in proportion to their frequency of consump tion by black and white NHANES II participants. We found black-white d ifferences in the frequency of consumption of foods within 14 food gro ups. However, blacks and whites had different average total fat densit ies for only 1 of the 14 food groups, no difference in saturated fat d ensities for any food group, and different vitamin A densities for 2 f ood groups. Among blacks and whites, there is no advantage to calculat ing ethnic-specific average nutrient densities for food groups compris ed of foods with similar densities. The present analysis could be appl ied to other ethnic populations when designing diet history questionna ires for multiethnic studies.