Use of adjustment factors with a brief food frequency questionnaire to obtain nutrient values.

The 100-item National Cancer Institute (Block) Food Frequency Questionnaire was created to measure an individual's relative nutrient intake as well as absolute nutrient values. A 60-item, brief questionnaire was then developed; its results correlate well with results from the 100-item questionnaire and with food record data. Adjustment factors, presented here, were developed that allow investigators to use the shorter questionnaire while obtaining nutrient values nearer the correct absolute values than those from the brief questionnaire alone. Data from the National Health and Nutrition Examination Survey II (1976-1980) and the first quarter of the National Health Interview Survey (1987) were used in developing the adjustment factors. The brief questionnaire was administered to approximately 22,000 subjects in the National Health Interview Survey. When the adjustment factors were applied to data from the second, third, and fourth quarters of the National Health Interview Survey, the adjusted values of 17 micro- and macronutrients were on average within 0.51% and 1.17% of estimates obtained by 24-hour recall in the National Health and Nutrition Examination Survey II, for men and women, respectively. Correlations between the adjusted nutrient values and absolute nutrient consumption, as measured by diet diaries in three smaller studies, were nearly the same or somewhat better than correlations with the unadjusted brief questionnaire.