The method of triads was applied to obtain the validity coefficients (VC) of the FFQ for specific fatty acids. A subsample was randomly selected from an earlier cross-sectional study. The FFQ and 3d dietary records were used for dietary assessment, and the fatty acid composition of erythrocyte membranes was determined as the biomarker.
The Spearman correlation coefficients between the FFQ and 3d dietary records were moderate to good (r = 0·28–0·66). The VC of the FFQ estimated by the method of triads were 0·72, 0·61, 0·65, 0·75 and 0·67 for MUFA, total n-6 fatty acids, α-linolenic acid, EPA and DHA, respectively. The VC could not be calculated for SFA, PUFA and total n-3 fatty acids because of negative correlations among the three measurements. But, the correlations between the FFQ and the dietary records were moderate for these fatty acids.