Estimating nutrient intake from a food frequency questionnaire: incorporating the elements of race and geographic region.

Assignment of nutrient values to food frequency questionnaire (FFQ) items does not usually account for participant characteristics (besides age or sex) that may influence eating patterns. For the Southern Community Cohort Study, the authors developed and assessed results from a nutrient database system incorporating sex-, race-, and census-region-specific food lists, using 24-hour recall data from the National Health and Nutrition Examination Survey (NHANES III, NHANES 1999-2000, NHANES 2001-2002, and NHANES 2003-2004) and the Continuing Survey of Food Intakes by Individuals that permitted estimation of nutrients tailored to participants' characteristics. For each of 15 nutrients, comparisons were made to a "standard" nutrient scoring system based on nationwide race-blind 24-hour recalls from these same sources. Using FFQ data from 67,926 Southern Community Cohort Study participants (47,038 African-American, 20,888 non-Hispanic white) aged 40-79 years who enrolled in the study during 2002-2008, the region- and race-informed system tended to produce increased estimated intake for most nutrients for black women, particularly for saturated fat (7.1%), monounsaturated fat (8.3%), and polyunsaturated fat (7.2%); smaller but significant changes (<5%) were also observed for nutrient intake for men and white women. These types of refinements in nutrient databases can be considered a means of enhancing the accuracy of dietary estimation using FFQs.