To validate an FFQ to assess antioxidant intake in overweight postmenopausal women.

A seventy-four-item antioxidant 1-month FFQ was developed based on major antioxidant sources in the American diet. Forty overweight postmenopausal women participated in a 9-month observational study and completed four sets of FFQ and 7 d food record (7dFR) every 3 months. Twelve-hour fasting blood was collected for plasma antioxidant measurement at the first visit.

Connecticut, USA.

Forty overweight postmenopausal women.

Spearman correlation coefficients of 1-month antioxidant intake estimated from the first set of FFQ and 7dFR ranged from 0·34 to 0·87, except for γ-tocopherol. The proportion of participants categorized into the extremely opposite tertiles averaged 7 %. Significant correlations were observed for diet–plasma vitamin C, α-tocopherol and carotenoids (P < 0·05). No time effect was observed on the dietary antioxidant intakes estimated from four 7dFR and four FFQ. Dietary antioxidants estimated from averaged four 7dFR showed moderate to high correlation with those estimated from averaged four FFQ and from each FFQ collected every 3 months. Bland–Altman plots did not show any systematic bias. Averaged misclassifications were below 10 % between these two instruments.

These findings attested a reasonable validity and a good acceptance of this 1-month FFQ in assessing both short-term and long-term diverse antioxidant intakes in these overweight postmenopausal women. The use of this FFQ in associating antioxidant intake with disease risk needs further investigation.

To validate a brief FFQ developed for capturing short-term antioxidant intake in a sample of US college students.

A seventy-four-item antioxidant FFQ was developed based on major antioxidant sources in the American diet. The FFQ was validated against 30 d food records (FR) and plasma antioxidant concentrations. The reliability of the FFQ was evaluated by two FFQ administered at a 1-month interval.

University of Connecticut, CT, USA.

Sixty healthy college students.

Estimates of dietary antioxidants from the FFQ were moderately to highly correlated with those estimated from the 30 d FR (r = 0·29–0·80; P < 0·05) except for γ-tocopherol and β-cryptoxanthin. Total antioxidant capacity from diet only or from diet and supplements estimated by the 30 d FR and FFQ were highly correlated (r = 0·67 and 0·71, respectively; P < 0·0001). The FFQ categorized 91 % of participants into the same or adjacent tertiles of antioxidant intake as the 30 d FR. Most dietary carotenoids estimated from the FFQ were correlated with plasma levels (P < 0·05). Correlation coefficients for test–retest reliability ranged from 0·39 to 0·86. More than 94 % of the participants were classified in the same or adjacent tertiles between the two administrations of the FFQ.

The brief FFQ demonstrated reasonable validity for capturing a comprehensive antioxidant intake profile. This FFQ is applicable in epidemiological or clinical studies to capture short-term antioxidant intake or to simply document the variations of antioxidant intake in intervention trials. Cross-validation studies are warranted in other target populations.