Validation of the omega-3 fatty acid intake measured by a web-based food frequency questionnaire against omega-3 fatty acids in red blood cells in men with prostate cancer

Abstract

Background/Objectives: The objective of this study was to evaluate the ability of a web-based self-administered food frequency questionnaire (web-FFQ) to assess the omega-3 (ω-3) fatty acids (FAs) intake of men affected with prostate cancer (PCa) against a biomarker. Subjects/Methods: The study presented herein is a sub-study from a phase II clinical trial. Enrolled patients afflicted with PCa were included in the sub-study analysis if the FA profiles from the red blood cell (RBC) membranes and FA intakes at baseline were both determined at the time of the data analysis (n=60). Spearman's correlation coefficients were calculated to estimate the correlations between FA intakes and their proportions in the RBC membranes. Results: Intakes of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were highly correlated with their respective proportions in the RBC membranes (both r s =0.593, P<0.0001). Correlation between alpha-linolenic acid (ALA) intake and its proportion in RBC was not significant (r s =0.130, P=0.332). Correlations were observed between fatty fish intake and total ω-3 FAs (r s =0.304, P=0.02), total long-chain ω-3 FAs (r s =0.290, P=0.03) and DHA (r s =0.328, P=0.01) in RBC membranes. Conclusions: This study has shown that the web-FFQ is an accurate tool to assess total long-chain ω-3 FAs, EPA and DHA but not ALA intake in clinical trials and epidemiological studies carried out in men with PCa.