Omega-3 (fish oil)
Oily fish first; a supplement if you don't eat fish. Evidence for sport is mixed
What it is
Omega-3s are polyunsaturated fatty acids. Research focuses on three: ALA from plant oils, and the long-chain EPA and DHA found in fish and fish oil.
Benefits
Supplements lower triglycerides and might reduce the risk of some cardiovascular events, especially in people who get little omega-3 from food (NIH). For sport the evidence is mixed: less muscle soreness after hard exercise is possible but not a consistent finding (IOC), and supplements may not help muscle growth in young adults (ISSN).
Dose
The US has no set intake for EPA and DHA, only for ALA: 1.6 g a day for men and 1.1 g for women (NIH). Europe recommends 250–500 mg of EPA+DHA a day for adults (EFSA). AIS: at least 500–600 mg of EPA+DHA a day; if you can't manage oily fish 2–3 times a week, supplement with 1000 mg or more of EPA+DHA a day.
When to take it
Take the capsules with a normal meal: that maximises absorption of EPA and DHA (AIS). The sources give no advice on time of day.
Who it's for
People who don't eat oily fish 2–3 times a week, and those on a plant-based diet, who most likely have a low omega-3 status (AIS). Vegans can use algal oil instead of fish oil: it also provides EPA and DHA.
Who can skip it
People who eat oily fish regularly: the EPA and DHA you need can come from ordinary food (AIS). The IOC notes it is unclear whether athletes should take a supplement in place of fish in the diet.
Forms
Omega-3s are sold as natural triglycerides, ethyl esters, re-esterified triglycerides, free fatty acids and phospholipids; the sources are fish oil, krill oil, cod liver oil and algal oil. NIH ODS: triglycerides and free fatty acids have somewhat higher bioavailability than ethyl esters, but all forms significantly raise blood EPA and DHA. A 2015 review: a difference between krill oil and fish oil is possible, but there is too little data for a firm conclusion.
Safety
No upper level has been set. EFSA and the FDA consider up to 5 g of EPA+DHA a day from supplements safe for adults. Side effects are usually mild: unpleasant taste, heartburn, nausea, diarrhoea. In two large trials, 4 g a day for several years slightly raised the risk of atrial fibrillation in people with heart disease or at high risk of it. If you take warfarin or other anticoagulants, talk to your doctor first (NIH).
From regular food
This is a summary of public sources, not medical advice. If you have a health condition, are pregnant or take medication, talk to a doctor before taking a supplement.
Sources
- Omega-3 Fatty Acids — Fact Sheet for Health Professionals . NIH Office of Dietary Supplements, 2025.
- AIS Sports Supplement Framework — Group B . Australian Institute of Sport, 2026.
- Scientific Opinion on the Tolerable Upper Intake Level of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and docosapentaenoic acid (DPA) . European Food Safety Authority, 2012.
- IOC consensus statement: dietary supplements and the high-performance athlete . International Olympic Committee / British Journal of Sports Medicine, 2018.
- International Society of Sports Nutrition Position Stand: Long-Chain Omega-3 Polyunsaturated Fatty Acids . International Society of Sports Nutrition, 2025.
- Comparison of bioavailability of krill oil versus fish oil and health effect . Vascular Health and Risk Management, 2015.
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