Estimation of daily human intake of food flavonoids.

The daily intake of food flavonoids was determined using a semiquantitative food frequency questionnaire (FFQ) and a 4-day food record (4DFR) in a group of 45 female Flemish dietitians. The subjects were asked to report their food intake three times: day 1 using the FFQ (FFQ1); between days 2 and 13 using a 4-day non-consecutive food diary (4DFR); and again using the FFQ on day 14 (FFQ2). The total flavonoid intakes (mean and standard deviation) as estimated with the different methods were: for FFQ1, 166.0 +/- 146.6 mg/day; for 4DFR, 203.0 +/- 243.2 mg/day; and for FFQ2, 158.3 +/- 151.8 mg/day. There was a significant different estimate for the amount of flavan-3-ols, flavanones and flavones when comparing the two FFQs with the 4DFR. The two research methods classified 88% of the 45 dietitians in the same or in an adjacent quartile for total flavonoid intake. The findings of this study indicate that the developed FFQ seems to be a simple and reliable method to assign subjects in quartiles of flavonoid intake.