In 30 seconds
- In 16 trained cyclists, 8 weeks of fish oil lowered heart rate and the oxygen used to pedal at the same intensity.
- In 26 amateur long-distance runners, 12 weeks of omega-3 doubled their omega-3 index, from 5.8 to 11.6%, and their VO2 peak rose from 53.6 to 56.0 ml/kg/min; with placebo, the change was not significant.
- With a low dose, around 700 mg of EPA and DHA a day, 8 weeks raised the omega-3 index and lowered the oxygen used per watt in a 5-minute time trial.
- It's a habit measured in weeks: a 2020 review found more consistent results from 6-8 weeks of daily intake.
If you run or cycle, omega-3 has mostly been studied for how your heart works during exercise. In trained cyclists, 8 weeks of fish oil lowered heart rate and the oxygen used at the same intensity 1, and in amateur runners, 12 weeks raised VO2 peak 2.
These are the effects of weeks of daily intake, not of one softgel on race day. If what you're after is better recovery from a hard session, you'll find it in omega-3 and exercise and omega-3 and muscle soreness. Here we focus on endurance: heart rate, oxygen and performance.
Why it matters if you do endurance sport
EPA and DHA, the two omega-3s found in fish, are built into the membranes of your cells, including muscle cells 3. Their level is measured with the omega-3 index: the percentage of EPA and DHA in your red blood cells 3.
This index rises slowly, over weeks of intake, and in the athletes in these studies it was not high. In the trained cyclists of one study it started at 4.2-4.7% 3, and in the amateur runners of another, at 5.8% 2. From food, European adults get on average up to 400-500 mg of EPA and DHA a day 6.
What was measured in cyclists
Lower heart rate at the same intensity
In a trial with 16 well-trained cyclists, half took 8 g of fish oil a day for 8 weeks, and the rest took olive oil 1. That works out at about 0.8 g of EPA and 2.4 g of DHA a day 5. With fish oil 1:
- Heart rate fell when pedalling at a steady pace and in the test to exhaustion, including peak heart rate.
- Whole-body oxygen consumption fell at submaximal intensity.
- The rate-pressure product, an indirect measure of how much oxygen the heart needs, fell.
VO2 peak and time to exhaustion were similar in both groups. What changed was the cost: the same work, with a lower heart rate and less oxygen 1.
A low dose also moved the index
Another trial gave 26 trained men two capsules a day of DHA-rich tuna oil, around 560 mg of DHA and 140 mg of EPA, for 8 weeks. The control group took soybean oil 3.
Their omega-3 index went from 4.7 to 6.3%, while in the control group it fell from 4.2 to 3.9%. In a 5-minute time trial, the oxygen used per 100 watts fell by 154 ml per minute with omega-3, compared with 23 ml with placebo. Average power was similar in both groups 3.
Elite cyclists: 3 weeks
In 13 elite cyclists, 3 weeks of omega-3 improved the function of the endothelium, the inner lining of the arteries, and maximal oxygen uptake, compared with placebo 4.
What was measured in runners
The most recent trial was carried out with 26 amateur long-distance runners, men aged 29 or over, during 12 weeks of training. One group took around 2,234 mg of EPA and 916 mg of DHA a day; the other took a medium-chain triglyceride oil as a placebo 2.
- Omega-3 index: it doubled, from 5.8 to 11.6%.
- VO2 peak: it rose from 53.6 to 56.0 ml/kg/min in the omega-3 group. In the placebo group, the change was not significant.
- Running economy: taking both groups together, its change was linked to the rise in the omega-3 index.
- 1,500 metres: times were similar in both groups.
The changes showed up in the runner's physiology, not in a short 1,500 m test 2.
| Study | Who | Dose and duration | What changed |
|---|---|---|---|
| Peoples et al., 2008 | 16 well-trained cyclists | 8 g of fish oil a day (0.8 g of EPA and 2.4 g of DHA), 8 weeks | Lower heart rate and less oxygen at the same intensity |
| Hingley et al., 2017 | 26 trained men, cycling | Around 700 mg of EPA and DHA a day, 8 weeks | Omega-3 index from 4.7 to 6.3% and less oxygen per watt in a 5-minute time trial |
| Żebrowska et al., 2015 | 13 elite cyclists | Omega-3 vs placebo, 3 weeks | Better endothelial function and higher VO2 max |
| Tomczyk et al., 2023 | 26 amateur long-distance runners | Around 3.15 g of EPA and DHA a day, 12 weeks | Omega-3 index from 5.8 to 11.6% and VO2 peak from 53.6 to 56.0 ml/kg/min |
Changes in the omega-3 group; in Tomczyk, VO2 peak also rose slightly with placebo, but not significantly.
How much to take and how long it takes
Endurance studies used between about 0.7 and 3.2 g of EPA and DHA a day 1 2 3. A 2020 review found more consistent results from 6-8 weeks of intake and with more than 1.5-2 g a day 5. Even so, the low-dose trial, with around 700 mg, already changed the omega-3 index and the oxygen used per watt 3. The same is true of other supplements you take daily: L-carnitine also takes weeks to work.
For the full picture:
- 250 mg a day of EPA and DHA is the adequate intake for heart health in healthy adults, according to EFSA 6.
- Up to 5 g a day of EPA and DHA from supplements raises no safety concerns for adults 6.
- Our 3 softgels provide 900 mg, 3.6 times the reference and more than the low-dose trial.
Work out what you already get from fish with the omega-3 calculator.
EPA and DHA a day
The dose in endurance studies and the dose in our omega-3
Heart, brain and vision: what the EU recognises
If you've been running or cycling for years, looking after your heart is part of the plan. EPA and DHA have authorised health claims in the EU 7:
- “EPA and DHA contribute to the normal function of the heart.” The beneficial effect is obtained with a daily intake of 250 mg of EPA and DHA.
- “DHA contributes to maintenance of normal brain function” and “DHA contributes to the maintenance of normal vision”. The beneficial effect is obtained with a daily intake of 250 mg of DHA.
A varied and balanced diet and a healthy lifestyle are important.
How to fit it in if you run or cycle
- Every day, with a meal. Its effect comes from weeks of intake, not from the dose on any one day.
- Leave plenty of time before your goal. If you're preparing for a race or a sportive, start early: the changes were measured at 8 and 12 weeks 1 2.
- No changes on race day. Take it as you would on any other day.
- Oily fish in your week. Every portion counts; we tell you which species to choose in mercury in fish.
- The basics first. Carbohydrates, water and electrolytes decide your race day. You'll find them in the running nutrition guide and the cycling nutrition guide.
Our Anchovy Omega-3
Our Anchovy Omega-3 provides 900 mg of EPA and DHA in 3 softgels: 540 mg of EPA and 360 mg of DHA, with 40 mg of vitamin E. It's anchovy oil, made in Spain with IFS Food and BRCGS Food Safety certification. It costs €21.90 for 90 softgels, a month's supply, about €0.73 a day.
If you take anticoagulants or other medication, or you are pregnant, check with your doctor first.
Frequently asked questions
Is omega-3 good for runners?
In a trial with 26 amateur long-distance runners, 12 weeks of omega-3 doubled their omega-3 index and their VO2 peak rose from 53.6 to 56.0 ml/kg/min, while in the placebo group the change was not significant.
Is omega-3 useful for cycling?
In studies with trained cyclists, it changed the cost of the effort: after 8 weeks, a lower heart rate and less oxygen to pedal at the same intensity. In a trial with elite cyclists, 3 weeks improved blood vessel function and VO2 max.
How much omega-3 should a runner or cyclist take?
How long does omega-3 take to make a difference if I run or cycle?
Weeks. The changes were measured after 8 and 12 weeks of daily intake, and a 2020 review found them more consistent from 6-8 weeks.
Should I take omega-3 on race day?
Take it as you would on any other day, with a meal. Its effect comes from weeks of daily intake, not from that day's dose, so there's no need to change anything before you start.
Sources
- Peoples GE, McLennan PL, Howe PRC, Groeller H. Fish oil reduces heart rate and oxygen consumption during exercise. J Cardiovasc Pharmacol. 2008;52(6):540-547. View publication
- Tomczyk M, Jost Z, Chroboczek M, et al. Effects of 12 wk of omega-3 fatty acid supplementation in long-distance runners. Med Sci Sports Exerc. 2023;55(2):216-224. View publication
- Hingley L, Macartney MJ, Brown MA, McLennan PL, Peoples GE. DHA-rich fish oil increases the omega-3 index and lowers the oxygen cost of physiologically stressful cycling in trained individuals. Int J Sport Nutr Exerc Metab. 2017;27(4):335-343. View publication
- 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. View publication
- Thielecke F, Blannin A. Omega-3 fatty acids for sport performance: are they equally beneficial for athletes and amateurs? A narrative review. Nutrients. 2020;12(12):3712. View publication
- EFSA. EFSA assesses safety of long-chain omega-3 fatty acids. Press release, 27 July 2012. View publication
- Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods. View publication
Information based on published studies. It does not replace the advice of a doctor or registered dietitian. The results describe what was measured in each study, not the properties of any specific product.
