Evaluation of an FFQ for assessment of antioxidant intake using plasma biomarkers in an ethnically diverse population

Objective: To evaluate FFQ estimates of dietary intake of individual antioxidants, fruit and vegetables in comparison to plasma concentrations of each antioxidant, and to determine which individual foods are associated with plasma antioxidant concentrations. Design: Dietary (alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein/zeaxanthin, lycopene, retinol, and vitamin E) intakes over 12 months were estimated from a 121-item FFQ. Correlation coefficients, corrected for within-person variability in diet and plasma antioxidants, were used to examine associations between antioxidant concentrations in diet and plasma. Setting: Melbourne Collaborative Cohort Study (MCCS). Results: Correlation coefficients for the carotenoids ranged from 0.28 for lycopene to 0.46 for beta-cryptoxanthin. There was no association between dietary and plasma retinol or dietary vitamin E with plasma alpha- and gamma-tocopherol. Individual plasma carotenoid concentrations were associated with intakes of fruit and vegetables. Conclusions: Our data suggest that the FFQ provides useful information on intakes of each of the carotenoids: alpha-carotene, beta-carotene, beta-cryptoxanthin, lycopene and lutein/zeaxanthin. There was no association between diet and plasma markets of retinol or vitamin E; this may reflect the importance of factors other than intake in modifying circulating levels of these nutrients.