The fish oils eicosapentaenoic acid (EPA, C20:5 (n-3)) and docosahexaenoic acid (DHA, C22:6 (n-3)) are thought to be cardioprotective because they reduce systemic inflammation. However sex differences exist between the benefits they confer on men and women. For example in a recent study published in the Journal of Nutrition1, investigators assessed the long term benefits of fish oil supplement on platelet aggregation in men and women. Subjects had baseline readings taken, and then consumed an EPA rich supplement containing 1000 mg of EPA and 200 mg of DHA per day or a DHA rich supplement containing 1000 mg DHA and 200 mg EPA per day. After 4 weeks of supplementation, the EPA and DHA rich supplements reduced platelet aggregation by 11.8 % and 14.8 %, respectively, compared to the placebo. In men the EPA supplement reduced the platelet aggregation by 18.9 % after 4 weeks supplement compared to the placebo. However, in men the DHA supplement was not as effective at raising plasma DHA levesl when compared to women.
Analysis of the fatty acids absorption showed that EPA accumulated to an equal concentration in the plasma fatty acids of both men and women, but women were able to accumulate higher concentrations of DHA compared to men. The ability of DHA to accumulate to a greater extent in women compared to men explains the differences seen for the efficiency of DHA supplements to affect platelet aggregation. The obvious reason for this would be the difference in the sex hormone concentrations between men and women. Administration of testosterone has been shown to diminish plasma DHA concentrations and to increase thromboxane receptor density and platelet aggregation in healthy males. In addition, women of childbearing age have been shown to have higher plasma concentrations of DHA compared to men, but lower concentrations of EPA. Administration of oestrogen has also been shown to increase plasma levels of DHA. Testosterone may increase the oxidation of DHA, reducing its availability and platelet inhibiting effects.