DHA has a greater effect than EPA on the omega-3 index
A wide variety of studies have shown that the omega-3 index is inversely related to the risk of heart disease and coronary mortality. This index is the sum of the erythrocyte concentration of the polyunsaturated fatty acids (PUFA) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in relation to total fatty acid concentration, expressed as a percentage. Measuring levels in the erythrocyte membrane is preferred to determination in plasma because the former has proved to be a better reflection of omega-3 PUFA intake. An index of 8% is considered the minimum for a good EPA and DHA status.
Recent research suggests that EPA and DHA have different effects on cardiometabolic risk factors. The aim of this study was to compare the effects of EPA with DHA supplementation on abdominal obesity and subclinical inflammation. To do this, 48 men and 106 women with abdominal obesity and subclinical inflammation were randomly assigned to a sequence of three treatment phases (in a double blind, repeated measure design): 1-2.7 g/d of EPA, 2-2.7 g/d of DHA and 3-3 g/d of corn oil (0 g of EPA+DHA). The treatment phases lasted 10 weeks and were separated by washout periods of 9 weeks. The rise in the omega-3 index, measured at the start and end of each phase, after DHA supplementation was significantly greater than after EPA supplementation (P<0.0001) and the increase obtained with both was higher than with placebo (P<0.0001 and P<0.0001). The difference in effect of EPA and DHA tended to be greater in men.
This greater DHA effect is consistent with its greater potency in modulating cardiometabolic risk factors.