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Does fish oil prevent heart disease? Large trials disagree

Large trials disagree. Pooled data show little overall effect on heart events, and high-dose omega-3 raises atrial fibrillation risk.

Published October 2026

Short answer

Standard omega-3 supplements show little or no overall effect on major heart events. High-dose prescription EPA lowered some events but raised irregular heartbeat risk. Evidence grade C (Limited). Pooled trials of ordinary omega-3 supplements show little effect and prescription EPA trials are mixed; downgraded for inconsistency and indirectness.

Key takeaways

  • Across 86 trials of about 163,000 people, increasing omega-3 intake, mostly through capsules, had little or no effect on cardiovascular events [1].
  • In REDUCE-IT, high-dose prescription EPA lowered the rate of a composite heart-event end point in statin-treated adults with high triglycerides [2].
  • Omega-3 supplements raised the risk of atrial fibrillation in trials, and the rise was larger above 1 g a day [3].
  • In VITAL, a large US trial in adults without prior heart disease, 1 g a day of marine omega-3 did not significantly reduce major cardiovascular events [4].
  • Eating fish is linked to lower coronary heart disease risk in cohort studies, which cannot prove cause and effect [5].

The short version

Omega-3 supplements, mostly fish oil capsules, show little or no overall effect on major heart events in pooled trials [1]. Some trials of high-dose prescription EPA found fewer heart events, but REDUCE-IT also found more people hospitalised for atrial fibrillation or flutter, an irregular heartbeat [2], and marine omega-3 trials overall found more atrial fibrillation [3].

What the studies show

A 2020 Cochrane review pooled 86 randomised trials with 162,796 people, most testing omega-3 capsules for at least a year. It found no clear effect on cardiovascular events (risk ratio 0.96, 95% CI 0.92 to 1.01) [1]. An earlier Cochrane review reached the same conclusion and said earlier signs of benefit seemed to come from trials at higher risk of bias [6].

The picture is different for prescription EPA. In REDUCE-IT, 8,179 adults with high triglycerides who were taking statins received 4 g a day of icosapent ethyl or placebo. The main composite end point occurred in 17.2% versus 22.0% over a median of 4.9 years (hazard ratio 0.75) [2]. The trial was funded by Amarin Pharma [2].

A 2024 meta-analysis of 18 trials found that omega-3 supplements lowered coronary revascularization (risk ratio 0.90), heart attacks (0.89) and cardiovascular death (0.92), and that EPA alone did better than EPA with DHA [7].

A 2026 trial of 1,228 people on maintenance haemodialysis found that 4 g a day of fish oil lowered serious cardiovascular events compared with corn-oil placebo (hazard ratio 0.57) [8]. It is a single trial, in people on dialysis [8].

The nuances

Form may matter. The 2024 meta-analysis of 15 trials credited the benefit mainly to prescription EPA ethyl ester, and warned that this form carries a higher bleeding risk [9].

Dose is not settled. The Cochrane review found no difference in effect by dose [1], while a 2021 meta-analysis found the atrial fibrillation risk rose with dose [3].

The atrial fibrillation signal is mixed. A 2021 meta-analysis of 7 trials with 81,210 people found that marine omega-3 supplements raised the risk of atrial fibrillation (hazard ratio 1.25), and the rise was larger in trials above 1 g a day (hazard ratio 1.49) [3]. In an atrial fibrillation substudy of VITAL, which tested 460 mg of EPA and 380 mg of DHA a day, the rise was not statistically significant (hazard ratio 1.09, 95% CI 0.96 to 1.24) [10]. In a Japanese open-label trial of icosapent ethyl, new atrial fibrillation occurred in 3.1% of the EPA group and 1.6% of controls [11]. In a pooled analysis of 17 cohorts with 54,799 people, higher blood DHA was linked to lower atrial fibrillation risk, while EPA was not [12].

Bleeding was also higher in REDUCE-IT, with serious bleeding in 2.7% versus 2.1%, a gap that did not reach statistical significance (P=0.06) [2].

Eating fish is a separate question. A 2020 meta-analysis of 22 cohort studies with 918,783 people found that higher fish intake was linked to about 9% lower coronary heart disease incidence (risk ratio 0.91) [5]. Cohort studies show an association, not cause and effect [5].

What this means for you

In VITAL, a trial of 25,871 adults in primary prevention, 1 g a day of marine omega-3 did not significantly reduce major cardiovascular events (hazard ratio 0.92) [4]. The trials that found benefit tested prescription EPA or fish oil in people with high triglycerides on statins, or in people on dialysis [2][8].

If you have heart disease, high triglycerides, a heart rhythm problem or take blood thinners, talk to a doctor before starting an omega-3 supplement. The rhythm and bleeding signals above are the reasons [2][3]. For dosage, side effects and interactions, see the fish oil topic page.

Go deeper

  • Fish Oil — Fish oil rich in EPA eases symptoms of depression in adults, a modest benefit supported by low-certainty evidence.

References

  1. Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease.. Cochrane Database Syst Rev, 2020.
  2. Cardiovascular Risk Reduction with Icosapent Ethyl for Hypertriglyceridemia.. N Engl J Med, 2019.
  3. Effect of Long-Term Marine ɷ-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.
  4. Marine n-3 Fatty Acids and Prevention of Cardiovascular Disease and Cancer.. N Engl J Med, 2019.
  5. Fish Consumption and Coronary Heart Disease: A Meta-Analysis.. Nutrients, 2020.
  6. Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease.. Cochrane Database Syst Rev, 2018.
  7. Effects of omega-3 fatty acids on coronary revascularization and cardiovascular events: a meta-analysis.. Eur J Prev Cardiol, 2024.
  8. Fish-Oil Supplementation and Cardiovascular Events in Patients Receiving Hemodialysis.. N Engl J Med, 2026.
  9. Efficacy and Safety of Omega-3 Fatty Acids in the Prevention of Cardiovascular Disease: A Systematic Review and Meta-analysis.. Cardiovasc Drugs Ther, 2024.
  10. Effect of Marine Omega-3 Fatty Acid and Vitamin D Supplementation on Incident Atrial Fibrillation: A Randomized Clinical Trial.. JAMA, 2021.
  11. Randomized Trial for Evaluation in Secondary Prevention Efficacy of Combination Therapy-Statin and Eicosapentaenoic Acid (RESPECT-EPA).. Circulation, 2024.
  12. Omega-3 Fatty Acid Biomarkers and Incident Atrial Fibrillation.. J Am Coll Cardiol, 2023.