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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 hasn't shown a clear benefit. 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 we found 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-3s are a family of fats. The short-chain one, ALA, comes from plant foods such as flaxseed, chia seeds and walnuts. The long-chain ones include EPA, DPA and DHA, and oily fish are the main food source of EPA and DHA[4]. The NHS names salmon, sardines, trout and mackerel among the oily fish, the richest source of long-chain omega-3[5]. The body converts little ALA: the ISSN cites research in young men in which 5–10% became EPA and 2–5% DHA[4].

Supplements are mostly fish oil. A standard fish oil holds about 180 mg of EPA and 120 mg of DHA per 1,000 mg, about 30% omega-3. Krill oil carries its omega-3 mostly as phospholipids, and algal oil, grown in fermentation vessels, often has more DHA than EPA and suits vegetarians. The ISSN says all these forms raise EPA and DHA in the blood[4].

Quality varies. Of 32 fish oils sold in New Zealand, only 3 held at least the EPA and DHA on the label, and 83% were over the limit for peroxide value, a marker of oxidation[6]. Of 171 products sold in Canada, half of those that could be tested exceeded voluntary oxidation limits, and unflavoured capsules had lower oxidation markers than bulk and flavoured oils[7]. The AIS advises keeping capsules in date, cool and out of direct light[8].

The Australian Institute of Sport lists fish oil in Group B of its framework: emerging or mixed scientific support, deserving consideration in specific situations[8].

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[9], 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[10]. We found no survey of UK or recreational runners.

Low levels are common in athletes. The omega-3 index is the share of EPA and DHA in the fats of red blood cells[11]. All but one of 106 German elite winter endurance athletes were below 8%[11]; about a third of 404 US college American football players were below 4%, and none were above 8%[12]; elite Canadian rugby sevens players averaged 4.54%[13]. These are blood markers: the IOC notes no sign that lower omega-3 levels impair performance[9].

In 275 recreational runners, higher omega-3 levels went with fewer self-reported injuries over 12 months, an association that can't show cause and effect[14]. Head impacts are another talking point, though not in running. In US college American football, trials tracked neurofilament light, a blood marker of nerve-fibre damage, over a season: the authors judged that DHA likely lessened its rise in one[15], a non-randomised study found a smaller rise with a supplement[16], and a placebo-controlled trial found no difference[17]. In 40 teenagers after a sport-related concussion, DHA didn't significantly change recovery time[18].

The claims, checked against the research

  • Faster race timesNot supported

    No trial we found has shown it. In amateur distance runners, 12 weeks of omega-3 didn't improve 1,500 m time more than a placebo[1], and trials in soccer players, Australian Rules footballers and young adults found no gain in running tests or a cycling time trial[19][20][21].

  • Better running economyMixed

    One small trial found it: oxygen cost at 12 km/h fell with omega-3, a significant difference from placebo, but 1,500 m time didn't improve[1]. In trained cyclists, fish oil lowered oxygen use during steady cycling without changing time to fatigue[22], while a krill oil trial found no change in oxygen uptake during cycling[21].

  • A higher VO2maxMixed

    Not in runners: VO2peak rose no more than with placebo[1], and trials in soccer players and cyclists found no change[19][22]. A few small trials did find a rise, including one in 50 overweight women on an exercise programme[23][4].

  • Less muscle sorenessMixed

    Results are inconsistent. One meta-analysis of 12 trials found a drop below the smallest difference considered meaningful[2]. Another found a moderate-to-large drop in 9 pooled placebo-controlled trials, but judged the evidence as a whole equivocal because of weak study designs[3].

  • Strength back soonerMixed

    The evidence is split. One meta-analysis found strength recovered better with omega-3[3]; another found no difference[2]. After downhill running, one trial found no strength difference[24], and another found leg press held up better with EPA or DHA alone, but not combined[25].

  • Less inflammationMixed

    Studies disagree. Across 43 recovery studies, some found lower inflammation markers such as IL-6 or TNF-α with omega-3 and others found no difference[3]. The ISSN says supplements don't reduce measures of inflammation after muscle-damaging exercise[4], and markers didn't differ from control after a marathon[26] or downhill running[24][25].

  • Fewer running injuriesNot studied

    No trial has tested it. One observational study linked a higher omega-3 index with fewer self-reported injuries in recreational runners, which can't show cause and effect[14].

How does omega-3 work?

EPA and DHA are built into cell membranes, at different speeds in different tissues. In 10 men taking 5 g of fish oil a day, blood levels rose within 1 week, while muscle levels had risen by week 2 and were still rising at week 4[27]. Fat tissue takes months[4].

In the 12-week runner trial, the omega-3 index doubled, from 5.8% to 11.6%[1]. In American football players given 6 g of DHA a day, it levelled off after about 15 weeks[28].

For endurance, the idea is that omega-3 in muscle membranes and mitochondria might lower the oxygen cost of exercise[4]. Some trials found lower heart rate, oxygen use or oxygen cost during steady exercise, but in none of them did performance improve[22][20][1].

For recovery, EPA and DHA are the raw material for molecules, such as resolvins and protectins, that help switch inflammation off[4]. Yet the ISSN finds the soreness evidence equivocal and no fall in inflammation measures 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 trial in soccer players and a krill oil cycling trial also found no performance gain[19][21]. 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]. The authors note their runners usually raced 10 km to the marathon and weren't used to 1,500 m[1].

In team-sport players, fish oil didn't improve a running performance test in soccer players[19], or time to exhaustion in treadmill runs at 2,200 m time-trial pace in Australian Rules footballers[20].

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, and the control group took nothing rather than a placebo[26].

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[24] or downhill running plus jumping lunges[25].

Study by study

The main studies on this page. What they took is what the study gave, not advice for any individual.
StudyWho took partWhat they tookWhat was measuredWhat they found
Tomczyk 2023 [1]Randomised controlled trial26 male amateur distance runners aged 29 to 42About 2.2 g EPA and 0.9 g DHA a day for 12 weeks, v an MCT oil placebo1,500 m time trial, VO2peak and running economy at 12 km/hNo gain in 1,500 m time or VO2peak over placebo. Oxygen cost at 12 km/h fell (47.6 to 46.5 ml/kg/min) and rose slightly, not significantly, with placebo; the change differed between groups. The omega-3 index doubled.Funding: Public grant (National Science Centre, Poland)
Raastad 1997 [19]Randomised controlled trial28 well-trained male soccer players aged 18 to 355.2 g of fish oil concentrate (1.6 g EPA, 1.04 g DHA) a day for 10 weeks, v corn oilMaximal aerobic power, anaerobic threshold and a running performance testNo difference between the groups on any test.
Buckley 2009 [20]Randomised controlled trial25 elite Australian Rules footballers6 g of DHA-rich fish oil a day for 5 weeks, v sunflower oilHeart rate at 10 km/h; treadmill runs to exhaustion at 2,200 m time-trial paceHeart rate in steady running fell more (by 7.8 v 1.9 beats a minute). No extra gain in time to exhaustion.
Peoples 2008 [22]Randomised controlled trial16 well-trained male cyclists8 g of fish oil a day (eight 1 g capsules) for 8 weeks, v olive oilVO2peak; heart rate and oxygen use cycling at 55% of peak workload to fatigueLower heart rate and oxygen use in steady cycling. No change in VO2peak, peak workload or time to fatigue.
Da 2015 [21]Randomised controlled trial37 young adults (19 men, 18 women)2 g of krill oil a day (about 240 mg EPA and 120 mg DHA) for 6 weeks, v placebo oilCycling time trial, heart rate, oxygen uptake and immune markersNo difference from placebo in time-trial performance, heart rate or oxygen uptake, and no effects of sex. Two immune measures (PBMC IL-2 production and natural killer cell activity) were higher 3 hours after exercise with krill oil.Funding: Funded by the krill oil maker, which also supplied the capsules
Toft 2000 [26]Randomised controlled trial20 male marathon runners6 g of fish oil (3.6 g omega-3) a day for 6 weeks before the Copenhagen Marathon, v no supplement (no placebo)Blood cytokines, white cells and creatine kinase up to 3 hours after the raceNo difference between the groups. The trial reported blood markers, not race times.
Kyriakidou 2021 [24]Randomised controlled trial14 healthy young men3 g of omega-3 a day (2,145 mg EPA, 858 mg DHA) for 4 weeks, v a collagen placeboSoreness, leg strength, creatine kinase and TNF-α after 60 minutes of downhill runningSoreness was lower at 24 hours. Strength, creatine kinase and TNF-α did not differ from placebo.
Heileson 2024 [25]Randomised controlled trial30 young men4 g a day of EPA+DHA, EPA alone, DHA alone or placebo for 7 weeksSoreness, leg press, jumps and inflammation after downhill running plus jumping lungesEPA alone or DHA alone: less soreness at 48 hours and better leg press than placebo. EPA+DHA mix: no significant difference. Inflammation similar.
VanDusseldorp 2020 [29]Randomised controlled trial32 resistance-trained young adults (16 men, 16 women)2, 4 or 6 g of fish oil a day (6 g gave 2.4 g EPA and 1.8 g DHA) or placebo for about 7.5 weeksSoreness on a 10 cm scale, jump height and strength after eccentric leg exercise6 g: soreness 2.7 to 4.5 cm lower than placebo at 2, 24, 48 and 72 hours, and jump height back to baseline sooner, though it didn't differ between groups at any time point. 4 g: lower soreness at 24 and 72 hours.Funding: Funded by the ISSN and a supplement company that made the capsules
Lv 2020 [2]Meta-analysisMeta-analysis of 12 randomised trials: 145 people given omega-3, 156 controlsOmega-3 supplements or control before eccentric (muscle-damaging) exerciseSoreness on a 10-point scale, strength and range of motionSoreness 0.93 points lower, below the 1.4-point change taken as meaningful. No difference in strength or range of motion. Low-quality evidence.
Yaghoobi 2026 [3]Meta-analysis43 studies reviewed, 9 placebo-controlled trials pooled; 31 of 43 studies in men only18.8 mg to 6,400 mg of EPA+DHA a day, for 0 to 70 daysSoreness, creatine kinase, swelling, strength and range of motion at peak impairmentPooled: less soreness (a moderate-to-large effect, in the authors' words), lower creatine kinase (small) and better strength (small-to-moderate). The wider evidence was judged equivocal.
Anthony 2021 [30]Systematic reviewSystematic review of 15 studies of omega-3 and soreness after eccentric exerciseFish oil taken for at least 7 days before eccentric exerciseDelayed-onset muscle soreness, risk of bias, and quality on a 5-point scaleResults looked favourable, but only one study met current design standards for omega-3 research.
Davinelli 2023 [14]Observational study275 recreational runners, average age 41, not taking omega-3None: an observational studyOmega-3 index and self-reported running injuries over 12 monthsA higher index went with fewer injuries: an association, not cause and effect.

The key studies, in order

  1. 1997Trial28 well-trained male soccer players, 10 weeks of fish oil v corn oil: no difference in maximal aerobic power, anaerobic threshold or running performance. [19]
  2. 2000Trial20 male marathon runners, 6 weeks of fish oil: no difference in inflammation or muscle damage markers after the Copenhagen Marathon. [26]
  3. 2002Non-randomised trialTracer study in 6 young men: ALA was converted to EPA and DPA, but no DHA was detected over 21 days. [33]
  4. 2002Non-randomised trialTracer study in young women: about 21% of labelled ALA became EPA and 9% DHA, suggesting women convert more than men. [32]
  5. 2008Trial32 adults, 600 mg of DHA a day for 2 weeks: algal-oil capsules and cooked salmon raised blood DHA by similar amounts. [36]
  6. 2008Trial16 trained male cyclists, 8 weeks of fish oil v olive oil: lower heart rate and oxygen use in steady cycling; VO2peak and time to fatigue unchanged. [22]
  7. 2009Trial25 elite Australian Rules footballers, 5 weeks of DHA-rich fish oil: lower heart rate during steady running, but no gain in time to exhaustion. [20]
  8. 2011SurveyFinnish Olympic athletes: omega-3 use rose from 11% in 2002 to 19% in 2009. [10]
  9. 2014Non-randomised trial10 men, 5 g of fish oil a day: blood omega-3 rose within 1 week; muscle omega-3 had risen by week 2 and was still rising at week 4. [27]
  10. 2014Observational study106 German national elite winter endurance athletes at screening: all but one had an omega-3 index below 8%. [11]
  11. 2015Observational study32 fish oils sold in New Zealand: only 3 held at least the labelled EPA and DHA, and only 8% stayed within all the oxidation limits. [6]
  12. 2015Trial37 men and women, 6 weeks of krill oil: no change in cycling time-trial performance v placebo. Funded by the krill oil maker. [21]
  13. 2015Observational study171 omega-3 products sold in Canada: half of those that could be tested exceeded voluntary oxidation limits; unflavoured capsules fared better than bulk and flavoured oils. [7]
  14. 2015Non-randomised trial165 vegans: average omega-3 index 3.7%, higher in women; a vegetarian EPA+DHA supplement raised it from 3.1% to 4.8% over 4 months. [34]
  15. 2016Trial50 overweight women on an 8-week aerobic exercise and diet programme: VO2max rose more with omega-3 than with placebo. [23]
  16. 2016Trial81 US college American football players, DHA or placebo over a season: the authors judged DHA likely lessened rises in a blood marker of nerve-fibre damage. [15]
  17. 2017Systematic review52 publications: fish oil reduced platelet aggregation in healthy people, but in randomised trials it did not increase bleeding during or after surgery. [37]
  18. 2017TrialUntrained women, 6 g of fish oil a day v placebo oil: soreness after resistance exercise was lower, but not significantly. [31]
  19. 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. [9]
  20. 2019Observational study404 US college American football players: 34% had an omega-3 index below 4%, and none above 8%. [12]
  21. 2020Meta-analysis12 trials: soreness was slightly lower with omega-3, but the drop was below the smallest difference considered meaningful. Low-quality evidence. [2]
  22. 2020Trial32 resistance-trained adults, 2, 4 or 6 g of fish oil a day or placebo: 6 g lowered soreness after eccentric exercise. Part-funded by a supplement company. [29]
  23. 2021Systematic review15 studies of omega-3 and soreness: results looked favourable, but only one study met current design standards. [30]
  24. 2021Observational study34 elite Canadian rugby sevens players (15 women): average omega-3 index 4.54%, slightly higher in women. [13]
  25. 2021Meta-analysis7 large trials, 81,210 people averaging 65 years: omega-3 supplements were linked to more atrial fibrillation, especially above 1 g a day. [38]
  26. 2021Non-randomised trialNon-randomised, two US college American football teams: a blood marker of nerve-fibre damage rose less in the team given an omega-3 supplement. [16]
  27. 2021Trial14 men, 4 weeks of omega-3 before downhill running: less soreness at 24 hours, but no difference in strength, power or muscle damage markers. [24]
  28. 2022Trial40 teenage athletes after a sport-related concussion, 2 g of DHA a day or placebo for 12 weeks: no significant difference in recovery time. [18]
  29. 2022Trial29 US college American football players, fish oil or placebo for 26 weeks: a blood marker of nerve-fibre damage rose in both groups; fish oil made no difference. [17]
  30. 2023Observational study275 recreational runners not taking omega-3: a higher omega-3 index went with fewer self-reported injuries over 12 months. An association only. [14]
  31. 2023Trial69 US college American football players, placebo or 2, 4 or 6 g of DHA a day: at 6 g, the omega-3 index levelled off by about 15 weeks. [28]
  32. 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]
  33. 2024Trial30 men, 4 g a day for 7 weeks: EPA alone or DHA alone lowered soreness after downhill running and lunges; the EPA+DHA mix didn't differ significantly from placebo. [25]
  34. 2025ConsensusISSN position stand: says omega-3 may enhance endurance capacity, but calls effects on endurance performance inconsistent and soreness evidence equivocal, and finds no fall in inflammation measures. [4]
  35. 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]

Who has the research been done in?

The running research is small and all male: 26 male amateurs aged 29 to 42 with 10 km times of 37 to 57 minutes in the one trial that timed runners[1], 20 men in the marathon trial[26], and healthy young men, not necessarily runners, in the downhill running trials[24][25].

The wider recovery research is mostly in untrained people. In the largest review, 58% of study groups were sedentary, 28% recreationally active, 9% trained and about 5% highly trained or elite, with average ages of 18.6 to 37.0 years[3].

So the findings may not apply to women, masters runners, teenagers or elite runners[1][3]. They may also differ for people who already eat oily fish: only 18 of the 43 studies measured omega-3 levels in the blood, and 3 used the omega-3 index[3].

What we know about women

Women are under-studied. In the largest review, 31 of 43 studies recruited only men, 7 men and women, and 5 only women, and the authors call for more research in female athletes[3]. All the running-based trials we found were in men[1][26][24][25]. In untrained women given 6 g of fish oil a day, soreness after resistance exercise was lower than with a placebo oil, but not significantly[31]. In overweight women exercising, VO2max rose more with omega-3 than placebo[23], and a krill oil trial with 18 women found no effects of sex[21]. We found no study of the menstrual cycle.

Women may make more of their own EPA and DHA. In a tracer study, young women converted an estimated 21% of a dose of ALA into EPA and 9% into DHA[32], while young men made no detectable DHA[33]. Vegan women had a slightly higher omega-3 index than vegan men[34]. For pregnancy, the NHS says not to take cod liver oil or supplements containing vitamin A[35], and to eat no more than 2 portions of oily fish a week[5].

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 four running-based trials we found were all in men[1][24][25][26].

The trials are small and often weak. Samples ranged from 8 to 64 people, and only 15 of 43 studies calculated the size they needed[3]. The runner trial's power calculation called for 36 people; 26 of 40 finished[1]. One review found only one of 15 soreness studies met current design standards[30], and a meta-analysis rated its evidence low quality[2].

Most outcomes are markers, not races, and the reviewers couldn't define an effective dose or duration: short and long courses and low and high doses all reported benefits[3].

Some studies had industry links: the krill oil trial was funded by its capsule maker[21], the dose trial partly by a supplement company[29], and several authors of the ISSN position stand declare industry links[4]. The runner trial was publicly funded[1].

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How and when is omega-3 used in studies?

Studies mostly used fish oil capsules, giving about 3 to 4 g of omega-3 a day in the runner and downhill running trials[1][24][25], and 2, 4 or 6 g of fish oil a day in a dose trial[29]. The IOC consensus lists about 2 g a day[9].

Across 43 recovery studies, daily EPA plus DHA ranged from 18.8 mg to 6,400 mg for 0 to 70 days, and the reviewers couldn't define an effective dose[3]. Product strength varies: a standard fish oil is about 30% omega-3, so 1 g of oil holds about 0.3 g of EPA and DHA[4].

Food is the other route. The NHS says a healthy diet should include at least 2 portions of fish a week, including 1 of oily fish[5], and the IOC suggests fatty fish in the diet may be a better choice for athletes than supplements[9].

For vegetarians and vegans, algal oil supplies EPA and DHA[4]. In 32 adults, 600 mg of DHA a day from algal-oil capsules raised blood DHA as much as cooked salmon over 2 weeks[36]. In vegans with a low index, 254 mg a day of a vegetarian EPA+DHA supplement raised it from 3.1% to 4.8% over 4 months[34].

When studies gave it

The main trials here gave omega-3 daily for weeks before testing, not as a single pre-race dose: 4 weeks[24], about 7 weeks[25][29] or 12 weeks[1]. That fits how it builds up: blood levels rise within a week, while muscle levels rise by week 2 and were still rising at week 4[27].

Within the day, trials split the capsules between morning and evening[1], or morning, lunch and evening[24]. The AIS tells practitioners that taking capsules with a normal meal helps absorption, and to re-test the omega-3 index no sooner than 12 weeks after a change, because red blood cells turn over slowly[8].

Both short courses (7 to 21 days) and longer ones (30 days or more) reported benefits for recovery, so the shortest course that works isn't known[3]. The AIS fact sheet says EPA and DHA in cell membranes are kept for about 2 weeks on average after intake stops[8].

What studies used. These are research protocols, not advice for any individual.
What studies usedWhenRef.
About 2.2 g EPA and 0.9 g DHA a day12 weeks, capsules morning and evening, in amateur runners[1]
3 g of omega-3 a day from fish oil (2,145 mg EPA, 858 mg DHA)4 weeks before downhill running, capsules morning, lunch and evening[24]
4 g a day of EPA, DHA or both7 weeks before downhill running[25]
2, 4 or 6 g of fish oil a day7 weeks before eccentric exercise, about 7.5 weeks in all[29]
6 g of fish oil (3.6 g of omega-3) a day6 weeks before a marathon[26]
About 2 g a dayIOC consensus table[9]

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[9].

Trials rarely reported side effects: in one meta-analysis, only 4 of 12 trials reported adverse events[2]. The AIS says studies using more than 5 g of oil a day have sometimes reported gut discomfort in a minority of participants, less likely when capsules are taken with food; liquid oil on its own is more likely to cause reflux and aftertaste[8]. Two people in one strength-training trial reported fishy burps[4].

Fish oil affects clotting. A review of 52 publications found it reduced platelet aggregation in healthy people, but randomised trials found no extra bleeding during or after surgery[37]. The AIS notes that EPA can affect how blood clots[8].

In 7 large long-term trials of 81,210 adults with an average age of 65, omega-3 supplements were linked to a higher risk of atrial fibrillation, an irregular heart rhythm, more so in trials using over 1 g a day[38].

Medicines and health conditions

Blood-thinning medicines are the main concern, as the IOC lists bleeding among the possible effects of fish oil supplements[9]. The NHS pages on warfarin and clopidogrel don't name fish oil[39][40]. The warfarin page says to tell your doctor about any vitamins or supplements[39]. The clopidogrel page says to tell your doctor or pharmacist, and that supplements that can affect the blood, such as ginkgo, might be a problem[40].

In pregnancy, the NHS says not to take cod liver oil or supplements containing vitamin A[35]. For people with a fish or seafood allergy, the AIS advises considering this before taking fish oil, and notes that some pre-operative assessments ask about fish oil use[8].

Be careful if

  • You're pregnant: the NHS says not to take cod liver oil or supplements containing vitamin A in pregnancy[35], 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[9], and the NHS says to tell your doctor about any supplements if you take warfarin[39], or your doctor or pharmacist if you take clopidogrel[40].
  • You have a fish or seafood allergy: the AIS advises considering this before taking fish oil[8].
  • You compete under anti-doping rules: any supplement can contain prohibited substances that aren't on the label, and athletes are responsible for anything found in their sample[9].
  • You use liquid or flavoured oils: in one analysis, bulk oils and flavoured products had higher oxidation markers than unflavoured capsules[7].

Is omega-3 allowed in competition?

Omega-3 and fish oil are not on the World Anti-Doping Agency's Prohibited List[41].

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[9].

Independent quality-assurance schemes, often called batch testing, check supplement products for prohibited substances[9]. WADA says using a product from one of these schemes can reduce, but not eliminate, the risk of an anti-doping violation[41], and the IOC says no product can be guaranteed entirely safe[9].

Myth or evidence?

5 things runners hear about omega-3. Pick an answer to see what the research says.

  1. 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. 2.Fish oil reduces muscle soreness.

    Show the answer

    Mixed. One meta-analysis found a drop below the smallest difference considered meaningful[2]. Another found a larger drop in 9 pooled trials but judged the wider evidence equivocal[3].

  3. 3.Omega-3 takes weeks to build up in your body.

    Show the answer

    Evidence. Muscle levels change within about two weeks[4], and in runners the omega-3 index doubled over 12 weeks[1].

  4. 4.Fish oil calms inflammation after hard exercise.

    Show the answer

    Mixed. Studies disagree. Some exercise trials found lower inflammation markers and others didn't[3]; the ISSN says supplements don't reduce measures of inflammation after muscle-damaging exercise[4].

  5. 5.Fish oil is banned in competition.

    Show the answer

    Myth. It is not on the WADA Prohibited List[41].

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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 didn't improve 1,500 m time compared with a placebo[1], and a trial in soccer players and one in cyclists found no gain either[19][22].
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[24].
Do runners with more omega-3 get fewer injuries?
Only one study we found has looked, and it can't show cause and effect. In 275 recreational runners, higher omega-3 levels went with fewer self-reported injuries, but the study was observational[14].
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].
Can you get enough omega-3 from food?
Food can supply EPA and DHA: the NHS says oily fish are the richest source of long-chain omega-3, and that a healthy diet should include at least 2 portions of fish a week, including 1 of oily fish[5]. The IOC suggests fatty fish may be a better choice for athletes than supplements[9].
Is fish oil banned in sport?
No. It is not on the WADA Prohibited List[41], though any supplement product can be contaminated[9].
What's the difference between EPA, DHA and ALA?
ALA is the short-chain omega-3 in plant foods such as flaxseed and walnuts; EPA and DHA are long-chain forms found mainly in oily fish[4]. The body turns only a little ALA into EPA, and less into DHA[4][33].
Is krill oil or algal oil different from fish oil?
Yes, in form and source, but we found no study showing either works differently for runners. Krill oil carries omega-3 mostly as phospholipids, algal oil often has more DHA than EPA[4], and a krill oil trial found no change in cycling performance[21].
Can vegetarians and vegans get EPA and DHA?
Yes, from algal oil[4]. The AIS says athletes on plant-based diets will most likely have low omega-3 status[8], and algal-oil capsules raised blood DHA as much as cooked salmon in a 2-week trial[36].
What is the omega-3 index?
It is the share of EPA and DHA in the fats of red blood cells, used in research as a measure of omega-3 status[11]. Runners in a 12-week trial went from 5.8% to 11.6%[1].
Is fish oil safe with blood thinners?
There's no simple yes. The IOC lists bleeding among the possible effects of fish oil supplements[9], and the NHS says to tell your doctor about any supplements if you take warfarin[39], or your doctor or pharmacist if you take clopidogrel[40].
Does fish oil go off?
It can oxidise. Of 171 omega-3 products sold in Canada, half of those that could be tested exceeded voluntary oxidation limits[7], and only 8% of fish oils tested in New Zealand stayed within all the limits[6].
Does omega-3 help with concussion?
The one trial we found after concussion saw no significant difference in recovery time: 40 teenagers took DHA or a placebo for 12 weeks[18]. None of the research is in runners. Trials in American football players tracked a blood marker of nerve-fibre damage over a season, with mixed results[15][17].

References

  1. [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. [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. [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. [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 statementISSN position stand: says omega-3 may enhance endurance capacity, but calls effects on endurance performance inconsistent and soreness evidence equivocal, and finds no fall in inflammation measures.

    doi.org/10.1080/15502783.2024.2441775
  5. [5]

    NHS Fish and shellfish. NHS, 2026.

    RegulatorAdvises at least 2 portions of fish a week, 1 of them oily, and no more than 2 oily portions for some groups. Oily fish are the richest source of long-chain omega-3.

    www.nhs.uk/live-well/eat-well/food-types/fish-and-shellfish-nutrition/
  6. [6]

    Albert BB, Derraik JG, Cameron-Smith D, et al. Fish oil supplements in New Zealand are highly oxidised and do not meet label content of n-3 PUFA. Scientific Reports, 2015.

    Observational study32 fish oils sold in New Zealand: only 3 held at least the labelled EPA and DHA, and only 8% stayed within all the oxidation limits.

    doi.org/10.1038/srep07928
  7. [7]

    Jackowski SA, Alvi AZ, Mirajkar A, et al. Oxidation levels of North American over-the-counter n-3 (omega-3) supplements and the influence of supplement formulation and delivery form on evaluating oxidative safety. Journal of Nutritional Science, 2015.

    Observational study171 omega-3 products sold in Canada: half of those that could be tested exceeded voluntary oxidation limits; unflavoured capsules fared better than bulk and flavoured oils.

    doi.org/10.1017/jns.2015.21
  8. [8]

    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
  9. [9]

    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
  10. [10]

    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.

    doi.org/10.1123/ijsnem.21.4.271
  11. [11]

    von Schacky C, Kemper M, Haslbauer R, Halle M Low omega-3 index in 106 German elite winter endurance athletes: a pilot study. International Journal of Sport Nutrition and Exercise Metabolism, 2014.

    Observational study106 German national elite winter endurance athletes at screening: all but one had an omega-3 index below 8%.

    doi.org/10.1123/ijsnem.2014-0041
  12. [12]

    Anzalone A, Carbuhn A, Jones L, et al. The omega-3 index in National Collegiate Athletic Association Division I collegiate football athletes. Journal of Athletic Training, 2019.

    Observational study404 US college American football players: 34% had an omega-3 index below 4%, and none above 8%.

    doi.org/10.4085/1062-6050-387-18
  13. [13]

    Armstrong A, Anzalone AJ, Pethick W, et al. An evaluation of omega-3 status and intake in Canadian elite rugby 7s players. Nutrients, 2021.

    Observational study34 elite Canadian rugby sevens players (15 women): average omega-3 index 4.54%, slightly higher in women.

    doi.org/10.3390/nu13113777
  14. [14]

    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: a higher omega-3 index went with fewer self-reported injuries over 12 months. An association only.

    doi.org/10.1080/17461391.2021.1998643
  15. [15]

    Oliver JM, Jones MT, Kirk KM, et al. Effect of docosahexaenoic acid on a biomarker of head trauma in American football. Medicine and Science in Sports and Exercise, 2016.

    Randomised controlled trial81 US college American football players, DHA or placebo over a season: the authors judged DHA likely lessened rises in a blood marker of nerve-fibre damage.

    doi.org/10.1249/MSS.0000000000000875
  16. [16]

    Heileson JL, Anzalone AJ, Carbuhn AF, et al. The effect of omega-3 fatty acids on a biomarker of head trauma in NCAA football athletes: a multi-site, non-randomized study. Journal of the International Society of Sports Nutrition, 2021.

    Non-randomised trialNon-randomised, two US college American football teams: a blood marker of nerve-fibre damage rose less in the team given an omega-3 supplement.

    doi.org/10.1186/s12970-021-00461-1
  17. [17]

    Mullins VA, Graham S, Cummings D, et al. Effects of fish oil on biomarkers of axonal injury and inflammation in American football players: a placebo-controlled randomized controlled trial. Nutrients, 2022.

    Randomised controlled trial29 US college American football players, fish oil or placebo for 26 weeks: a blood marker of nerve-fibre damage rose in both groups; fish oil made no difference.

    doi.org/10.3390/nu14102139
  18. [18]

    Miller SM, Zynda AJ, Sabatino MJ, et al. A pilot randomized controlled trial of docosahexaenoic acid for the treatment of sport-related concussion in adolescents. Clinical Pediatrics, 2022.

    Randomised controlled trial40 teenage athletes after a sport-related concussion, 2 g of DHA a day or placebo for 12 weeks: no significant difference in recovery time.

    doi.org/10.1177/00099228221101726
  19. [19]

    Raastad T, Høstmark AT, Strømme SB Omega-3 fatty acid supplementation does not improve maximal aerobic power, anaerobic threshold and running performance in well-trained soccer players. Scandinavian Journal of Medicine and Science in Sports, 1997.

    Randomised controlled trial28 well-trained male soccer players, 10 weeks of fish oil v corn oil: no difference in maximal aerobic power, anaerobic threshold or running performance.

    doi.org/10.1111/j.1600-0838.1997.tb00113.x
  20. [20]

    Buckley JD, Burgess S, Murphy KJ, Howe PR DHA-rich fish oil lowers heart rate during submaximal exercise in elite Australian Rules footballers. Journal of Science and Medicine in Sport, 2009.

    Randomised controlled trial25 elite Australian Rules footballers, 5 weeks of DHA-rich fish oil: lower heart rate during steady running, but no gain in time to exhaustion.

    doi.org/10.1016/j.jsams.2008.01.011
  21. [21]

    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 v placebo. Funded by the krill oil maker.

    doi.org/10.1371/journal.pone.0139174
  22. [22]

    Peoples GE, McLennan PL, Howe PR, Groeller H Fish oil reduces heart rate and oxygen consumption during exercise. Journal of Cardiovascular Pharmacology, 2008.

    Randomised controlled trial16 trained male cyclists, 8 weeks of fish oil v olive oil: lower heart rate and oxygen use in steady cycling; VO2peak and time to fatigue unchanged.

    doi.org/10.1097/FJC.0b013e3181911913
  23. [23]

    Haghravan S, Keshavarz SA, Mazaheri R, et al. Effect of omega-3 PUFAs supplementation with lifestyle modification on anthropometric indices and VO2max in overweight women. Archives of Iranian Medicine, 2016.

    Randomised controlled trial50 overweight women on an 8-week aerobic exercise and diet programme: VO2max rose more with omega-3 than with placebo.

    pubmed.ncbi.nlm.nih.gov/27179166/
  24. [24]

    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 before downhill running: less soreness at 24 hours, but no difference in strength, power or muscle damage markers.

    doi.org/10.1186/s12970-020-00405-1
  25. [25]

    Heileson JL, Harris DR, Tomek S, et al. Long-chain omega-3 fatty acid supplementation and exercise-induced muscle damage: EPA or DHA?. Medicine and Science in Sports and Exercise, 2024.

    Randomised controlled trial30 men, 4 g a day for 7 weeks: EPA alone or DHA alone lowered soreness after downhill running and lunges; the EPA+DHA mix didn't differ significantly from placebo.

    doi.org/10.1249/MSS.0000000000003332
  26. [26]

    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: no difference in inflammation or muscle damage markers after the Copenhagen Marathon.

    doi.org/10.1152/jappl.2000.89.6.2401
  27. [27]

    McGlory C, Galloway SD, Hamilton DL, et al. Temporal changes in human skeletal muscle and blood lipid composition with fish oil supplementation. Prostaglandins, Leukotrienes and Essential Fatty Acids, 2014.

    Non-randomised trial10 men, 5 g of fish oil a day: blood omega-3 rose within 1 week; muscle omega-3 had risen by week 2 and was still rising at week 4.

    doi.org/10.1016/j.plefa.2014.03.001
  28. [28]

    Lust CAC, Burns JL, Jones MT, et al. The dose-response effect of docosahexaenoic acid on the omega-3 index in American football athletes. Medicine and Science in Sports and Exercise, 2023.

    Randomised controlled trial69 US college American football players, placebo or 2, 4 or 6 g of DHA a day: at 6 g, the omega-3 index levelled off by about 15 weeks.

    doi.org/10.1249/MSS.0000000000003117
  29. [29]

    VanDusseldorp TA, Escobar KA, Johnson KE, et al. Impact of varying dosages of fish oil on recovery and soreness following eccentric exercise. Nutrients, 2020.

    Randomised controlled trial32 resistance-trained adults, 2, 4 or 6 g of fish oil a day or placebo: 6 g lowered soreness after eccentric exercise. Part-funded by a supplement company.

    doi.org/10.3390/nu12082246
  30. [30]

    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
  31. [31]

    Tinsley GM, Gann JJ, Huber SR, et al. Effects of fish oil supplementation on postresistance exercise muscle soreness. Journal of Dietary Supplements, 2017.

    Randomised controlled trialUntrained women, 6 g of fish oil a day v placebo oil: soreness after resistance exercise was lower, but not significantly.

    doi.org/10.1080/19390211.2016.1205701
  32. [32]

    Burdge GC, Wootton SA Conversion of alpha-linolenic acid to eicosapentaenoic, docosapentaenoic and docosahexaenoic acids in young women. British Journal of Nutrition, 2002.

    Non-randomised trialTracer study in young women: about 21% of labelled ALA became EPA and 9% DHA, suggesting women convert more than men.

    doi.org/10.1079/BJN2002689
  33. [33]

    Burdge GC, Jones AE, Wootton SA Eicosapentaenoic and docosapentaenoic acids are the principal products of alpha-linolenic acid metabolism in young men. British Journal of Nutrition, 2002.

    Non-randomised trialTracer study in 6 young men: ALA was converted to EPA and DPA, but no DHA was detected over 21 days.

    doi.org/10.1079/BJN2002662
  34. [34]

    Sarter B, Kelsey KS, Schwartz TA, Harris WS Blood docosahexaenoic acid and eicosapentaenoic acid in vegans: associations with age and gender and effects of an algal-derived omega-3 fatty acid supplement. Clinical Nutrition, 2015.

    Non-randomised trial165 vegans: average omega-3 index 3.7%, higher in women; a vegetarian EPA+DHA supplement raised it from 3.1% to 4.8% over 4 months.

    doi.org/10.1016/j.clnu.2014.03.003
  35. [35]

    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/
  36. [36]

    Arterburn LM, Oken HA, Bailey Hall E, et al. Algal-oil capsules and cooked salmon: nutritionally equivalent sources of docosahexaenoic acid. Journal of the American Dietetic Association, 2008.

    Randomised controlled trial32 adults, 600 mg of DHA a day for 2 weeks: algal-oil capsules and cooked salmon raised blood DHA by similar amounts.

    doi.org/10.1016/j.jada.2008.04.020
  37. [37]

    Begtrup KM, Krag AE, Hvas AM No impact of fish oil supplements on bleeding risk: a systematic review. Danish Medical Journal, 2017.

    Systematic review52 publications: fish oil reduced platelet aggregation in healthy people, but in randomised trials it did not increase bleeding during or after surgery.

    pubmed.ncbi.nlm.nih.gov/28552094/
  38. [38]

    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 averaging 65 years: omega-3 supplements were linked to more atrial fibrillation, especially above 1 g a day.

    doi.org/10.1161/CIRCULATIONAHA.121.055654
  39. [39]

    NHS Warfarin. NHS, 2026.

    RegulatorTell your doctor about any other medicines, herbal remedies, vitamins or supplements before taking warfarin. The page doesn't name fish oil.

    www.nhs.uk/medicines/warfarin/
  40. [40]

    NHS Taking clopidogrel with other medicines and herbal supplements. NHS, 2026.

    RegulatorSupplements that can affect the blood, such as ginkgo, might be a problem with clopidogrel; tell your doctor or pharmacist about supplements. Fish oil isn't named.

    www.nhs.uk/medicines/clopidogrel/taking-clopidogrel-with-other-medicines-and-herbal-supplements/
  41. [41]

    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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