Omega-3 supplementation raises Omega-3 index and lowers heart rate in male athletes, new study shows

In a study published earlier this week, researchers aimed to examine the effect of Omega-3 fatty acid supplementation on exercise physiology and the potential for improving performance¹. Prior research by the Fatty Acid Research Institute in conjunction with The Cooper Institute found a two-percentage point higher Omega-3 Index was associated with a 0.35 and 0.69 bpm greater heart rate recovery in men and women, respectively, when comparing 13,912 healthy participants over a over a 10-year period². Other research has shown positive effects from Omega-3 supplementation, the researchers for the current explain, such as lower submaximal exercise heart rate (HR), but various factors have impeded research on exercise physiology specifically. Additionally, one study also stated that between 11 and 100% of athletes consuming dietary supplements, the researchers also noted. The double blinded, block randomized parallel control trial, “Six weeks of either EPA-rich or DHA-rich Omega-3 supplementation alters submaximal exercise physiology in endurance trained male amateurs,” was published in Frontiers in Nutrition in August 2025.

The type of fish oil used as a source of Omega-3s in previous trials (EPA-rich or DHA-rich, for example) have varied, which may have contributed to differing results. Additionally, the type of placebo can make a difference, the researchers suggest. Coconut oil, used in this trial, was not high in Omega-3 or Omega-6, in order to avoid potentially altering Omega-3:6 absorption or incorporation into membranes.

In this study, 55 male amateur, endurance-trained athletes age 18–50 years from various disciplines were given capsules of either Eicosapentaenoic acid (EPA)-rich fish oil (consisting of 1.8 b of EPA and 1.2g of DHA per day), a Docosahexaenoic acid (DHA)-rich algae oil (consisting of 2 g of DHA and 1 g of EPA per day), or a coconut oil placebo with 3 g of fat per day for six weeks. A 24 km time trial (TT) was performed before and after the supplement period. After the supplement period, assessments were conducted on submaximal exercising HR, rating of perceived exertion (RPE), respiratory exchange ratio (RER), and TT performance.

The researchers hypothesized that Omega-3 levels would increase in the two test groups, but not in the placebo group; that HR would decrease in the DHA group only; and that TT performance would increase significantly in the test groups compared to placebo. The supplements used in the study were provided by Doetsch Grether AG.

Pre- and post-supplementation showed statistically significant changes in submaximal exercise physiology. Additionally, the change in Omega-3 levels was inversely correlated with HR and with RPE.

Highlighted results from the study include:

• The EPA and DHA supplements increased the Omega-3 index significantly, from 6% pre-intervention to an excess of 8% post-intervention, and the placebo did not have an effect
• Both of the supplements also lowered submaximal exercising HR and RPE, and no change was seen in the placebo group
• The EPA supplementation was the only one to increase RER, and no change was seen in the DHA or placebo groups
• TT improved for HR, RPE, and RER, but did not show significant gains

The current study was limited to male participants, limiting the generalization of the results, the researchers noted. Future studies should include female participants, which could examine the impact of sex-specific metabolic processes, they suggested.

Overall, the supplementation was demonstrated to increase Omega-3 index to a significant level and support cardiac efficiency, though DHA supplementation did not translate to performance improvements. “This study adds further evidence that both EPA and DHA can alter submaximal exercise physiology, but further research is required to determine their effects on exercise performance outcomes,” the researchers concluded.

References

1. Blannin, A.; Boulton, G.; Thielecke, F. Six weeks of either EPA-rich or DHA-rich Omega-3 supplementation alters submaximal exercise physiology in endurance trained male amateurs. Front. Nutr. 2025. 12:1588421. DOI: 10.3389/fnut.2025.1588421
2. Farrell, SW et al. “Higher omega-3 index is associated with more rapid heart rate recovery in healthy men and women.” Prostaglandins, Leukotrienes and Essential Fatty Acids, 2020 163. DOI: 10.1016/j.plefa.2020.102206