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Fish oil for the heart

Goal: What large trials used to lower the risk of heart attacks and other cardiovascular events, and why their results differ.

Each protocol describes what studies used, for one goal or for one group of people. It is not advice for you: talk to a doctor before you start a supplement.

Updated 4 Nov 2026
Dose

1 g of fish oil a day, with 840 mg of EPA and DHA, in VITAL and ASCEND.[1] 4 g a day of a prescription omega-3 in REDUCE-IT and STRENGTH.[1]

Form

Fish oil capsules in VITAL and ASCEND, against placebo.[2][3] Purified EPA as icosapent ethyl in REDUCE-IT, and an EPA and DHA product in STRENGTH.[1]

How long

3.5 to 7.4 years.[4][3]

What studies found

A Cochrane review of 86 trials and 162,796 people found 9% fewer coronary events, with low-certainty evidence. It found little or no effect on all cardiovascular events, stroke or death from any cause.[5] Results of 4 g a day differ: events were 17.2% against 22.0% in REDUCE-IT, and 12.0% against 12.2% in STRENGTH.[6][7]

Ask a doctor first

More than 1.5 g of EPA and DHA a day raised atrial fibrillation in people at high heart risk.[8] High doses of purified EPA raised bleeding by 0.6 percentage points.[9] Prescription products differ from supplements, so their results may not apply to supplements.[10]

People who have heart disease, take a blood thinner or take heart medicines should ask a doctor or pharmacist first.[1]

References

  1. Omega-3 Fatty Acids: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements. ods.od.nih.gov
  2. Marine n-3 Fatty Acids and Prevention of Cardiovascular Disease and Cancer. Manson JE, Cook NR, Lee IM, Christen W, Bassuk SS, Mora S, et al. N Engl J Med, 2019. PMID 30415637
  3. Effects of n-3 Fatty Acid Supplements in Diabetes Mellitus. Bowman L, Mafham M, Wallendszus K, Stevens W, Buck G, Barton J, et al. N Engl J Med, 2018. PMID 30146932
  4. Dietary supplementation with n-3 polyunsaturated fatty acids and vitamin E after myocardial infarction: results of the GISSI-Prevenzione trial. Gruppo Italiano per lo Studio della Sopravvivenza nell'Infarto miocardico. Lancet, 1999. PMID 10465168
  5. Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Abdelhamid AS, Brown TJ, Brainard JS, Biswas P, Thorpe GC, Moore HJ, et al. Cochrane Database Syst Rev, 2020. PMID 32114706
  6. Cardiovascular Risk Reduction with Icosapent Ethyl for Hypertriglyceridemia. Bhatt DL, Steg PG, Miller M, Brinton EA, Jacobson TA, Ketchum SB, et al. N Engl J Med, 2019. PMID 30415628
  7. Effect of High-Dose Omega-3 Fatty Acids vs Corn Oil on Major Adverse Cardiovascular Events in Patients at High Cardiovascular Risk: The STRENGTH Randomized Clinical Trial. Nicholls SJ, Lincoff AM, Garcia M, Bash D, Ballantyne CM, Barter PJ, et al. JAMA, 2020. PMID 33190147
  8. Effects of Omega-3 Fatty Acid Treatment on Risk for Atrial Fibrillation: An Updated Meta-Analysis of 35 Trials including 114 592 Individuals. Abuknesha NR, O'Keefe JH, Qian F, Tintle NL, Lin Y, Sun Y, et al. Circ Arrhythm Electrophysiol, 2026. PMID 42517224
  9. Bleeding Risk in Patients Receiving Omega-3 Polyunsaturated Fatty Acids: A Systematic Review and Meta-Analysis of Randomized Clinical Trials. Javaid M, Kadhim K, Bawamia B, Cartlidge T, Farag M, Alkhalil M J Am Heart Assoc, 2024. PMID 38742535
  10. Omega-3 Supplements: What You Need To Know. NIH National Center for Complementary and Integrative Health, 2024. www.nccih.nih.gov