Oxidation of plasma proteins is not increased after supplementation with eicosapentaenoic and docosahexaenoic acids

Background: It is generally thought that as the intake of dietary polyunsat urated fatty acids increases, so should that of alpha-tocopherol, to protec t the polyunsaturated fatty acids from increased in vivo peroxidation. Howe ver, there are little quantitative data about the concentration of alpha-to copherol that is necessary when eicosapentaenoic acid (EPA) and docosahexae noic acid (DHA) are consumed. Objective: The purpose of this study was to measure changes produced in 2 i ndexes of lipid oxidation after supplementation with EPA and DHA from fish oil and 3 doses of RRR-alpha-tocopheryl acetate in postmenopausal women. Design: Daily supplements of fish oil providing 2.5 g EPA and 1.8 g DHA and 0, 100, 200, or 400 mg alpha-tocopheryl acetate were given to 46 postmenop ausal women in a 3-treatment, 4-period crossover design. Results: The supplements increased plasma concentrations of EPA, DHA, and a lpha-tocopherol. The fish-oil supplement increased the plasma concentration of thiobarbituric acid-reactive substances (TBARS) (P = 0.0001) but not th at of oxidatively modified protein, as indicated by the carbonyl content. T he alpha-tocopheryl acetate and fish-oil supplements had no significant eff ect on plasma concentrations of TBARS or oxidized protein. Conclusions: Although these data show a small but statistically significant increase in oxidative stress on the basis of plasma TBARS concentrations a fter the consumption of EPA and DHA, the clinical relevance of this change is questionable. In addition, as supplements of alpha-tocopheryl acetate we re added to the diet, neither the plasma TBARS concentration nor the protei n oxidation changed. Consequently, the results of this study indicate that there is no basis fur vitamin E supplementation after consumption of EPA an d DHA.