Effects of docosahexaenoic acid supplementation on blood lipids, estrogen metabolism, and in vivo oxidative stress in postmenopausal vegetarian women

Abstract

Background: Vegetarians are generally deficient in long-chain n-3 fatty acids. Long-chain n-3 fatty acids have a beneficial effect on plasma lipid levels, and some studies showed that they had breast cancer suppression effect. One of the biomarkers of breast cancer risk is the ratio of urinary 2-hydroxyestrone (2-OHE1) to 16-hydroxyestrone (16-OHE1). Objective: To investigate the effect of docosahexaenoic acid (DHA, 22:6n-3) supplementation on blood lipids, estrogen metabolism and oxidative stress in vegetarians. Design: Single-blind, randomized, placebo-controlled trial. Interventions: Twenty-seven postmenopausal vegetarian women were recruited. After a 2-week run-in period with 6 g placebo corn oil, the subjects were subsequently randomized to receive either 6 g corn oil (n=13) or 6 g DHA-rich algae oil (2.14 g of DHA/day) (n=14) for 6 weeks. Two subjects in corn oil group withdrew before completion. Main outcome measures: Plasma lipids, urinary 2-OHE1 and 16-OHE1, urinary F2-isoprostanes and plasma -tocopherol. Results: Plasma LDL-DHA and EPA level increased significantly by DHA supplementation. DHA decreased plasma cholesterol (C) levels (P=0.04), but did not influence the levels of plasma TG, LDL-C and HDL-C, -tocopherol, urinary F2-isoprostanes, 2-OHE1, 16-OHE1 and ratio of 2-OHE1 to 16-OHE1 as compared to corn oil. Conclusion: DHA supplementation at a dose of 2.14 g/day for 42 days decreases plasma cholesterol but neither does it show beneficial effects on estrogen metabolism, nor does it induce deleterious effects on the observed in vivo antioxidant or oxidative stress marker in postmenopausal vegetarian women.