Dietary flavonoids and flavonoid-rich foods: validity and reproducibility of FFQ-derived intake estimates

Objective: To evaluate the validity and reproducibility of a 152-item semi-quantitative FFQ (SFFQ) for estimating flavonoid intakes. Design: Over a 1-year period, participants completed two SFFQ and two weighed 7-d dietary records (7DDR). Flavonoid intakes from the SFFQ were estimated separately using Harvard (SFFQ(Harvard)) and Phenol-Explorer (SFFQ(PE)) food composition databases. 7DDR flavonoid intakes were derived using the Phenol-Explorer database (7DDR(PE)). Validity was assessed using Spearman's rank correlation coefficients deattenuated for random measurement error (r ( s )), and reproducibility was assessed using rank intraclass correlation coefficients. Setting: This validation study included primarily participants from two large observational cohort studies. Participants: Six hundred forty-one men and 724 women. Results: When compared with two 7DDR(PE), the validity of total flavonoid intake assessed by SFFQ(PE) was high for both men and women (r ( s ) = 0 center dot 77 and r ( s ) = 0 center dot 74, respectively). The r ( s ) for flavonoid subclasses ranged from 0 center dot 47 for flavones to 0 center dot 78 for anthocyanins in men and from 0 center dot 46 for flavonols to 0 center dot 77 for anthocyanins in women. We observed similarly moderate (0 center dot 4-0 center dot 7) to high (>= 0 center dot 7) validity when using SFFQ(Harvard) estimates, except for flavones(Harvard) (r ( s ) = 0 center dot 25 for men and r ( s ) = 0 center dot 19 for women). The SFFQ demonstrated high reproducibility for total flavonoid and flavonoid subclass intake estimates when using either food composition database. The intraclass correlation coefficients ranged from 0 center dot 69 (flavonols(PE)) to 0 center dot 80 (proanthocyanidins(PE)) in men and from 0 center dot 67 (flavonols(PE)) to 0 center dot 77 (flavan-3-ol monomers(Harvard)) in women. Conclusions: SFFQ-derived intakes of total flavonoids and flavonoid subclasses (except for flavones) are valid and reproducible for both men and women.