Omega-3 for runners: what's being used and what the research says
We report what runners are using and what the research says. We don't recommend taking any supplement. Talk to your GP or a registered sports dietitian before trying one.
Quick answer
Research suggests any effects are small. In a 12-week trial in amateur distance runners, omega-3 did not improve 1,500 m time compared with a placebo[1]. Effects on soreness after muscle-damaging exercise are inconsistent: one meta-analysis found a drop too small to be meaningful[2], another a larger one but equivocal evidence overall[3].
- Research
- Emerging (proposed)Inconsistent effect on soreness after hard exercise. No faster times in the one trial that timed runners.
- Proposed by our editor; not yet confirmed by an expert reviewer.
- WADA status
- Permitted
- Distances in the research
- 800 m–5K: limited research10K–half: not studiedMarathon: limited researchUltra: not studied
What is omega-3?
Omega-3 supplements are mostly fish oil, which provides two fats called EPA and DHA. Krill oil and algal oil are other sources[4], and oily fish is the richest food source[5].
The Australian Institute of Sport lists fish oil in Group B of its framework: emerging or mixed scientific support, deserving consideration in specific situations[6].
Also called: fish oil, EPA, DHA, krill oil, algal oil.
Why is omega-3 getting attention?
The popular claim is that it calms inflammation after exercise[7], and the ISSN says athletes may be at higher risk of low omega-3 levels[4].
Among Finnish Olympic athletes, omega-3 use rose from 11% in 2002 to 19% in 2009[8].
In a study of 275 recreational runners, those with higher omega-3 levels reported fewer running injuries. It was observational, so it can't show that omega-3 caused the difference[9].
How does omega-3 work?
EPA and DHA are built into cell membranes. Muscle levels change within about two weeks of taking supplements, while fat tissue takes months[4].
The suggested benefits for runners are less soreness after muscle-damaging exercise and changes in muscle that might help endurance. The ISSN says evidence on soreness is equivocal, effects on endurance performance are inconsistent, and supplements don't reduce measures of inflammation after muscle-damaging exercise[4].
Does omega-3 improve running performance or recovery?
Not clearly. The only randomised trial we found that timed runners saw no faster 1,500 m than with a placebo[1], and a krill oil trial found no change in cycling time trials[10]. Results on soreness are inconsistent: one meta-analysis found a drop too small to be meaningful[2], while another found less soreness and better strength in 9 pooled trials but judged the wider evidence equivocal because of weak study designs[3].
800 m to 5K (Limited research)
In 26 amateur distance runners, 12 weeks of omega-3 didn't improve 1,500 m time compared with a placebo. Running economy improved, but VO2peak changed no more than with the placebo[1].
10K to half marathon (Not studied)
We found no omega-3 trials with a 10 km or half-marathon result. The runners in the 12-week trial raced 10 km, but were tested in the lab and over 1,500 m[1].
Marathon (Limited research)
In 20 male marathon runners, 6 weeks of fish oil before the Copenhagen Marathon made no difference to inflammation or muscle damage markers after the race. The trial reported blood markers, not race times[11].
Ultra (Not studied)
We found no omega-3 trials in ultra runners. The research on recovery uses exercise designed to cause muscle damage, such as an hour of downhill running[12].
The key studies, in order
- 2000Trial20 male marathon runners: 6 weeks of fish oil before the Copenhagen Marathon made no difference to inflammation or muscle damage markers after the race. [11]
- 2011SurveyFinnish Olympic athletes: omega-3 use rose from 11% in 2002 to 19% in 2009. Recovery was the main reason given for using nutritional supplements. [8]
- 2015Trial37 men and women, 6 weeks of krill oil: no change in cycling time-trial performance compared with a placebo. Funded by the krill oil maker. [10]
- 2018ConsensusOmega-3's effects on recovery are not consistent, and it is unclear whether athletes should supplement rather than eat fatty fish. Supplements can cause bleeding or digestive problems. [7]
- 2020Meta-analysis12 trials: soreness was slightly lower with omega-3, but the drop was below the smallest difference considered meaningful. Low-quality evidence. [2]
- 2021Systematic review15 studies of omega-3 and soreness: results looked favourable, but only one study met current design standards. [13]
- 2021Meta-analysis7 large trials, 81,210 people with an average age of 65: omega-3 supplements were linked to a higher risk of atrial fibrillation, more so above 1 g a day. [14]
- 2021Trial14 men, 4 weeks of omega-3 then 60 minutes of downhill running: soreness was lower at 24 hours, but strength, power and muscle damage markers didn't differ from a placebo. [12]
- 2023Observational study275 recreational runners not taking omega-3: higher omega-3 levels in the blood went with fewer self-reported running injuries over 12 months. An association, not cause and effect. [9]
- 2023Trial26 male amateur distance runners, 12 weeks: omega-3 doubled the omega-3 index and improved running economy, but 1,500 m time and VO2peak changed no more than with a placebo. [1]
- 2025ConsensusThe ISSN's position is that omega-3 has been shown to improve endurance capacity, but it says effects on endurance performance are inconsistent, soreness evidence is equivocal, and inflammation measures don't fall. [4]
- 2026Meta-analysis43 studies: effects on recovery equivocal, with weak designs. In 9 pooled placebo-controlled trials, less soreness, lower creatine kinase and better strength at peak impairment. 31 of 43 studies were men only. [3]
What the research can't tell us yet
Most participants were men: in the largest review, 31 of 43 studies included men only[3], and the three running-based trials we found were all in men[1][12][11].
The evidence on soreness is weak: one review found only one of 15 studies met current design standards[13], and a meta-analysis rated its evidence low quality[2].
Some studies were funded by supplement makers: the krill oil trial was funded by the company that supplied the capsules[10].
How is omega-3 used in studies?
The runner trial used about 2.2 g of EPA and 0.9 g of DHA a day for 12 weeks[1]. A downhill running trial used 3 g of omega-3 a day for 4 weeks[12], and the IOC consensus lists about 2 g a day[7].
The NHS says a healthy diet should include at least 2 portions of fish a week, including 1 of oily fish[5]. The IOC suggests fatty fish in the diet may be a better choice for athletes than supplements[7].
| What studies used | When | Ref. |
|---|---|---|
| About 2.2 g EPA and 0.9 g DHA a day | 12 weeks, in amateur distance runners | [1] |
| 3 g of omega-3 a day from fish oil | 4 weeks before downhill running | [12] |
| 6 g of fish oil (3.6 g of omega-3) a day | 6 weeks before a marathon | [11] |
What are the side effects, and who should be careful?
The IOC lists possible problems with fish oil supplements: heavy metal contaminants, bleeding, digestive problems and raised LDL cholesterol[7].
In large trials in older adults with or at risk of heart disease, omega-3 supplements were linked to a higher risk of atrial fibrillation, an irregular heart rhythm, more so at over 1 g a day[14].
Be careful if
- You're pregnant: the NHS says not to take cod liver oil or supplements containing vitamin A in pregnancy[15], and to eat no more than 2 portions of oily fish a week[5].
- You take blood-thinning medicines: the IOC lists bleeding among the possible effects of fish oil supplements[7], and the AIS notes that EPA can affect how blood clots[6].
- You have a fish or seafood allergy: the AIS advises considering this before taking fish oil[6].
Is omega-3 allowed in competition?
Omega-3 and fish oil are not on the World Anti-Doping Agency's Prohibited List[16].
The anti-doping risk with any supplement product is contamination: products can contain prohibited substances that aren't on the label, and athletes are responsible for anything found in their sample[7].
Independent quality-assurance schemes, often called batch testing, check supplement products for prohibited substances[7]. WADA says using a product from one of these schemes can reduce, but not eliminate, the risk of an anti-doping violation[16], and the IOC says no product can be guaranteed entirely safe[7].
Myth or evidence?
5 things runners hear about omega-3. Pick an answer to see what the research says.
1.Fish oil makes you run faster.
Show the answer
Myth. The only trial we found that timed runners saw no 1,500 m benefit over a placebo[1].
2.Fish oil reduces muscle soreness.
3.Omega-3 takes weeks to build up in your body.
4.Fish oil calms inflammation after hard exercise.
5.Fish oil is banned in competition.
Show the answer
Myth. It is not on the WADA Prohibited List[16].
Have you tried omega-3?
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Frequently asked questions
- Does fish oil make you run faster?
- Research suggests not: in a 12-week trial in amateur distance runners, omega-3 did not improve 1,500 m time compared with a placebo[1].
- Does omega-3 help with soreness after hard runs?
- Results are inconsistent. One meta-analysis found a drop in soreness below the smallest difference considered meaningful[2], and another found a larger drop in 9 pooled trials but judged the wider evidence equivocal[3]. In a downhill running trial, soreness was lower at 24 hours, but strength and muscle damage markers didn't differ[12].
- Do runners with more omega-3 get fewer injuries?
- In one study of 275 recreational runners, higher omega-3 levels went with fewer self-reported injuries, but it was observational, so it can't show that omega-3 prevents them[9].
- How long does omega-3 take to build up?
- Muscle levels change within about two weeks, while fat tissue takes months[4]. In the runner trial, the omega-3 index doubled over 12 weeks[1].
References
- [1]
Tomczyk M, Jost Z, Chroboczek M, et al. Effects of 12 wk of omega-3 fatty acid supplementation in long-distance runners. Medicine and Science in Sports and Exercise, 2023.
Randomised controlled trial26 male amateur distance runners, 12 weeks: omega-3 doubled the omega-3 index and improved running economy, but 1,500 m time and VO2peak changed no more than with a placebo.
doi.org/10.1249/MSS.0000000000003038 - [2]
Lv ZT, Zhang JM, Zhu WT Omega-3 polyunsaturated fatty acid supplementation for reducing muscle soreness after eccentric exercise: a systematic review and meta-analysis of randomized controlled trials. BioMed Research International, 2020.
Meta-analysis12 trials: soreness was slightly lower with omega-3, but the drop was below the smallest difference considered meaningful. Low-quality evidence.
doi.org/10.1155/2020/8062017 - [3]
Yaghoobi E, Pashaei F, Allsopp GL, et al. Effects of LC n-3 PUFA supplementation on muscle pain, function, and damage markers in healthy young to middle-aged adults following acute or chronic exercise: a systematic review and meta-analysis of randomized controlled trials. Nutrients, 2026.
Meta-analysis43 studies: effects on recovery equivocal, with weak designs. In 9 pooled placebo-controlled trials, less soreness, lower creatine kinase and better strength at peak impairment. 31 of 43 studies were men only.
doi.org/10.3390/nu18091447 - [4]
Jäger R, Heileson JL, Abou Sawan S, et al. International Society of Sports Nutrition position stand: long-chain omega-3 polyunsaturated fatty acids. Journal of the International Society of Sports Nutrition, 2025.
Consensus statementThe ISSN's position is that omega-3 has been shown to improve endurance capacity, but it says effects on endurance performance are inconsistent, soreness evidence is equivocal, and inflammation measures don't fall.
doi.org/10.1080/15502783.2024.2441775 - [5]
NHS Fish and shellfish. NHS, 2026.
RegulatorOily fish is the richest source of long-chain omega-3. A healthy diet includes at least 2 portions of fish a week, 1 of them oily; some groups should eat no more than 2 portions of oily fish.
www.nhs.uk/live-well/eat-well/food-types/fish-and-shellfish-nutrition/ - [6]
Australian Institute of Sport AIS Sports Supplement Framework: Group B and linked fact sheets. Australian Sports Commission, 2026.
Consensus statementLists fish oil (EPA and DHA) in Group B: emerging or mixed scientific support, deserving consideration in specific situations, with individual monitoring.
www.ausport.gov.au/ais/nutrition/supplements/group_b - [7]
Maughan RJ, Burke LM, Dvorak J, et al. IOC consensus statement: dietary supplements and the high-performance athlete. British Journal of Sports Medicine, 2018.
Consensus statementOmega-3's effects on recovery are not consistent, and it is unclear whether athletes should supplement rather than eat fatty fish. Supplements can cause bleeding or digestive problems.
doi.org/10.1136/bjsports-2018-099027 - [8]
Heikkinen A, Alaranta A, Helenius I, Vasankari T Dietary supplementation habits and perceptions of supplement use among elite Finnish athletes. International Journal of Sport Nutrition and Exercise Metabolism, 2011.
SurveyFinnish Olympic athletes: omega-3 use rose from 11% in 2002 to 19% in 2009. Recovery was the main reason given for using nutritional supplements.
doi.org/10.1123/ijsnem.21.4.271 - [9]
Davinelli S, Intrieri M, Ali S, et al. Omega-3 index and AA/EPA ratio as biomarkers of running-related injuries: an observational study in recreational runners. European Journal of Sport Science, 2023.
Observational study275 recreational runners not taking omega-3: higher omega-3 levels in the blood went with fewer self-reported running injuries over 12 months. An association, not cause and effect.
doi.org/10.1080/17461391.2021.1998643 - [10]
Da Boit M, Mastalurova I, Brazaite G, et al. The effect of krill oil supplementation on exercise performance and markers of immune function. PLOS ONE, 2015.
Randomised controlled trial37 men and women, 6 weeks of krill oil: no change in cycling time-trial performance compared with a placebo. Funded by the krill oil maker.
doi.org/10.1371/journal.pone.0139174 - [11]
Toft AD, Thorn M, Ostrowski K, et al. N-3 polyunsaturated fatty acids do not affect cytokine response to strenuous exercise. Journal of Applied Physiology, 2000.
Randomised controlled trial20 male marathon runners: 6 weeks of fish oil before the Copenhagen Marathon made no difference to inflammation or muscle damage markers after the race.
doi.org/10.1152/jappl.2000.89.6.2401 - [12]
Kyriakidou Y, Wood C, Ferrier C, et al. The effect of omega-3 polyunsaturated fatty acid supplementation on exercise-induced muscle damage. Journal of the International Society of Sports Nutrition, 2021.
Randomised controlled trial14 men, 4 weeks of omega-3 then 60 minutes of downhill running: soreness was lower at 24 hours, but strength, power and muscle damage markers didn't differ from a placebo.
doi.org/10.1186/s12970-020-00405-1 - [13]
Anthony R, Macartney MJ, Peoples GE The influence of long-chain omega-3 fatty acids on eccentric exercise-induced delayed muscle soreness: reported outcomes are compromised by study design issues. International Journal of Sport Nutrition and Exercise Metabolism, 2021.
Systematic review15 studies of omega-3 and soreness: results looked favourable, but only one study met current design standards.
doi.org/10.1123/ijsnem.2020-0238 - [14]
Gencer B, Djousse L, Al-Ramady OT, et al. Effect of long-term marine omega-3 fatty acids supplementation on the risk of atrial fibrillation in randomized controlled trials of cardiovascular outcomes: a systematic review and meta-analysis. Circulation, 2021.
Meta-analysis7 large trials, 81,210 people with an average age of 65: omega-3 supplements were linked to a higher risk of atrial fibrillation, more so above 1 g a day.
doi.org/10.1161/CIRCULATIONAHA.121.055654 - [15]
NHS Pregnancy vitamins and supplements. NHS, 2026.
RegulatorDo not take cod liver oil or supplements containing vitamin A when you're pregnant.
www.nhs.uk/pregnancy/keeping-well/pregnancy-vitamins-and-supplements/ - [16]
World Anti-Doping Agency The Prohibited List. World Anti-Doping Agency, 2026.
RegulatorThe substances and methods prohibited in sport. Omega-3 and fish oil are not on it.
www.wada-ama.org/en/prohibited-list
Who wrote and reviewed this
Written by Grant MacMillan, Editor, RunV. Not yet reviewed by an expert.
Last checked against its references . Next review due . How pages are reviewed · How we grade research
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