Verdict: A reasonable health supplement if you eat little oily fish, but not a proven way to raise VO2max or endurance performance.
Safety: Usually well tolerated; fishy burps and stomach upset are common, and talk to a doctor if you take blood thinners
Key takeaways
A 2020 systematic review of 32 trials in athletes found no clear effect of fish oil on endurance performance
In trained cyclists, 8 weeks of fish oil lowered heart rate and oxygen use during submaximal exercise without changing peak VO2
Omega-3s may help muscle recovery and inflammation markers, so think of them as a health supplement rather than a stamina booster
Omega-3 fish oil is one of the most widely used supplements in the world, and it is popular with runners and cyclists for heart health and recovery. The question here is narrower: does it raise VO2max or make you faster for longer? The honest answer is that the effects seen so far are modest, and performance gains have not been clearly shown.
What it is
Omega-3s are polyunsaturated fats. The two that matter most for the body are EPA and DHA, found mainly in oily fish such as salmon, mackerel, sardines and herring, and in fish, krill and algae oils. They are built into cell membranes in the heart and muscle, where they influence inflammation, blood vessel function and possibly the efficiency of oxygen use. A plant omega-3, ALA (from flax, chia and walnuts), is converted to EPA and DHA only in small amounts.
Does it raise VO2max?
Two trials are often quoted, and they disagree:
- Peoples and colleagues (2008) gave 16 well-trained male cyclists 8 g of fish oil or olive oil a day for 8 weeks. Fish oil lowered heart rate during incremental and steady exercise, and lowered whole-body oxygen consumption at a submaximal workload. But peak VO2 did not change, and neither did peak workload or time to fatigue.
- Żebrowska and colleagues (2015) gave 13 elite cyclists 1.3 g of omega-3 twice daily or placebo for 3 weeks. They reported improved blood vessel function, higher nitric oxide levels and higher VO2max. This was a small, short study, and the result has not been consistently replicated.
Taken together, fish oil may make the heart work a little less hard at a given effort, but there is no reliable evidence that it raises the ceiling itself. VO2max is driven mainly by cardiac output and blood volume (see what limits VO2max).
Does it improve endurance performance?
The best summary is a systematic review by Lewis and colleagues (2020) of 32 randomised placebo-controlled trials in athletes. It found fairly consistent effects on reaction time, mood, cardiovascular responses in cyclists, muscle recovery and some inflammation markers. It found no clear effects on endurance performance, lung function, muscle force or training adaptation. Few negative outcomes were reported.
So for runners asking "is omega-3 good for stamina?", the evidence says: possibly helpful for recovery between hard sessions, not a direct performance aid. A smarter use of the same effort is good recovery habits — see resting heart rate, HRV and recovery and enough sleep.
How it is used in studies
Athlete trials have used a wide range, from about 2.6 g a day of omega-3 for 3 weeks to 8 g of fish oil a day for 8 weeks. Because omega-3s build up in cell membranes slowly, effects take weeks rather than days. Labels list total fish oil and EPA plus DHA separately, and the EPA plus DHA amount is what matters when comparing products. Eating oily fish a couple of times a week is a food-first alternative.
Side effects, safety and anti-doping
- Common side effects: fishy aftertaste or burps, heartburn, nausea and loose stools.
- Bleeding: omega-3s can have a mild blood-thinning effect. Talk to a doctor if you take anticoagulants or antiplatelet drugs, have a bleeding disorder or are due for surgery.
- Quality: fish oils can oxidise (go rancid). Choose reputable brands and store as directed.
- Anti-doping: fish oil is not prohibited, but supplements can be contaminated. Competitive athletes should use third-party tested products.
This page is not medical advice. Talk to a doctor if you have a medical condition or take medication.
Who might benefit
- People who rarely eat oily fish, including many vegetarians (algae oil is a plant-based source of EPA and DHA)
- Athletes looking for small benefits in muscle recovery during heavy training blocks
- Anyone advised by their doctor to take omega-3s for heart or lipid reasons
If your goal is purely a higher VO2max, the money and attention are better spent on structured training such as VO2max workouts and mostly easy volume.
Bottom line
Omega-3s are a sensible health supplement if your diet is low in oily fish, and they may modestly help recovery and lower exercise heart rate. They have not been shown to raise VO2max or improve endurance performance in a consistent way. Compare other options on the supplements page, see the stronger evidence for caffeine, and track your fitness with the VO2max calculator.
Frequently asked questions
Is omega-3 good for runners?
It can be part of a healthy diet, and some studies show better muscle recovery and lower inflammation markers. But a systematic review of trials in athletes found no clear effect on endurance performance.
Does omega-3 increase stamina?
There is no good evidence that it does. In trained cyclists, fish oil lowered heart rate during exercise, but time to fatigue and peak power did not change.
Do omega-3 supplements raise VO2max?
Not reliably. One small 3-week study in cyclists reported a higher VO2max, but a larger 8-week trial found no change in peak oxygen uptake.
Should endurance athletes take fish oil?
If you rarely eat oily fish, it is a reasonable health choice. Talk to a doctor first if you take blood thinners or have a bleeding disorder, and use third-party tested products if you compete.
Sources
- Lewis NA, Daniels D, Calder PC, Castell LM, Pedlar CR. Are there benefits from the use of fish oil supplements in athletes? A systematic review. Adv Nutr. 2020. PMID 32383739.
- Peoples GE, McLennan PL, Howe PR, Groeller H. Fish oil reduces heart rate and oxygen consumption during exercise. J Cardiovasc Pharmacol. 2008;52(6):540–547. PMID 19034030.
- Żebrowska A, Mizia-Stec K, Mizia M, Gąsior Z, Poprzęcki S. Omega-3 fatty acids supplementation improves endothelial function and maximal oxygen uptake in endurance-trained athletes. Eur J Sport Sci. 2015;15(4):305–314.