Dietary fish intake and plasma phospholipid n-3 polyunsaturated fatty acid concentrations in men and women in the European Prospective Investigation into Cancer-Norfolk United Kingdom cohort

Background: The n-3 polyunsaturated fatty acids (n-3 PUFAs) docosahexaenoic acid and eicosapentaenoic acid, found in fish and fish-oil supplements and also formed by conversion of α-linolenic acid in soy and rapeseed (canola) oils, are thought to have cardioprotective effects. Objective: Because the relative feasibility and measurement error of dietary methods varies, this study compared fish and fish-oil intakes obtained from 4 dietary methods with plasma n-3PUFAs in men and women in a general population. Design: The study participants were 4949 men and women aged 40-79 y from the European Prospective Investigation into Cancer-Norfolk United Kingdom cohort. Measurements of plasma phospholipid n-3 PUFA concentrations and fish intakes were made with the use of 4 dietary methods (food-frequency questionnaire, health and lifestyle questionnaire, 7-d diary, and first-day recall from the 7-d diary). Results: Amounts of fish consumed and relations with plasma phospholipid n-3 PUFAs were not substantially different between the 4 dietary methods. Plasma n-3 PUFA concentrations were significantly higher in women than in men, were 20% higher in fish-oil consumers than in non-fish-oil consumers, and were twice as high in fatty fish consumers as in total fish consumers. Only ≈25% of the variation in plasma n-3 PUFA was explained by fish and fish-oil consumption. Conclusions: This large study found no substantial differences between dietary methods and observed clear sex differences in plasma n-3 PUFAs. Because variation in n-3 PUFA was only partially determined by fish and fish-oil consumption, this could explain the inconsistent results of observational and intervention studies on coronary artery disease protection.