A semiquantitative food frequency questionnaire is a valid indicator of the usual intake of hytoestrogens by south asian women in the uk relative to multiple 24h dietary recalls and multiple plasma samples
A semiquantitative food frequency questionnaire is a valid indicator of the usual intake of hytoestrogens by south asian women in the uk relative to multiple 24-h dietary recalls and multiple plasma samples. We investigated the relative validity of an interview-administered FFQ to estimate phytoestrogen intake among South Asian women in the UK. A population-based sample of 108 healthy South Asian women completed random repeated monthly 24h recalls with a subsample also providing multiple plasma samples over a period of 1 y followed by administration of the FFQ. The FFQ produced slightly higher estimates of phytoestrogen intake than the 24h recalls, but the percentage of women classified into the same 1 quartile by the 2 methods was high for all phytoestrogens from 81 to 94 percent with only a small percentage being misclassified into extreme opposite quartiles. Energy-adjusted Spearman correlations coefficients between the estimates obtained by the FFQ and the 24h recalls were for genistein, 060 for daidzein, 070 for secoisolariciresinol, and 0.63 for matairesinol all P 0.001. Spearman correlation coefficients between the FFQ estimates and plasma levels were 0.21 P 0.12 for genistein, 0.32 P 0.02for daidzein and 0.10 P 0.43 for enterolactone; the corresponding values for the 24-h recalls compared with plasma levels were 0.43 P 0.001 0.40 P 0.002, and 0.08 P 0.50, respectively. The method of triads was used to estimate the validity coefficients VCs between the estimates provided by each assessment method and “true intake.” The FFQ had the highest VC for lignans 0.91 vs. 0.73 for 24h recalls and 0.11 for plasma samples and satisfactory VCs for both genistein 0.46 vs. 0.95 and 0.45, respectively and daidzein 0.67 vs. 0.83 and 0.45, respectively. This FFQ is thus a relatively valid tool with which to estimate phytoestrogen intake among South Asian women in the UK.