Objective: To assess the effects of high-fish and low-fish diets on plasma concentrations of fatty acids and selected antioxidants.
Design and subjects: The effects of fish consumption on dietary and plasma antioxidant levels and fatty acid composition were studied as part of a large dietary survey of Finnish adults (n = 1861). High-fish consumers were matched with low-fish consumers and 41 pairs were identified. The members of each pair were of the same sex, from the same 10 y age group, and from the same or adjacent areas. There were 21 men and 20 women in each group, with a mean age of 54.3 y.
Methods: The fish consumption of the subjects was investigated with a qualitative food questionnaire. Additionally, a 3 d food record was used to estimate the diet. Two indices were defined to describe the oxidation potential of the diets. The plasma alpha-tocopherol, gamma-tocopherol, and beta-carotene concentrations and various fatty acids were analysed.
Results: The mean fish intake was 103 g/d in the high-fish and 5 g/d in the low-fish group. The dietary intakes of vitamin C, protein, total n-3 polyunsaturated fatty acids (PUFA), eicosapentaenoic acid, docosahexaenoic acid, mercury, selenium, and salt and the theoretical oxidative potential were higher (P < 0.05) and the saturated fatty acid intake lower (P < 0.01) in the high-fish than in the low-fish group. The dietary vitamin E intake was similar in both groups but the ratio of dietary vitamin E/PUFA was higher (P < 0.01) in the high-fish than in the low-fish group (0.85 and 0.75, respectively). The plasma n-3 PUFAs were higher (P < 0.001) and n-6 PUFAs lower (P < 0.001) in the high-fish than in the low-fish group. There were no differences in plasma antioxidant levels between the groups.
Conclusion: This study shows that extreme fish consumption does not affect plasma antioxidant levels.