Based on the effects of n-3 polyunsaturated fatty acids (PUFA) such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on reduction of blood viscosity, we theorized that PUFA could improve aerobic performance by increasing oxygen supply to tissues.

Twenty male subjects were randomly divided into two groups (n = 10): a fish oil group (FG) and a control (CG). Maximal oxygen uptake and oxygen uptake during submaximal exercise were measured using a cycle ergometer. For 8 weeks, the FG then ingested capsules containing 3.6 g/day of EPA-rich fish oil, while the CG took 3.6 g/day of a medium-chain triglyceride.

After supplementation, erythrocyte EPA and DHA in the FG were significantly increased. In the FG, a negative linear correlation was detected in the change between erythrocyte EPA and whole oxygen uptake during submaximal exercise pre- and post-supplementation.

The present study showed that EPA-rich fish oil supplementation improves exercise economy in humans.