What the research on omega-3 supplements found
In trials, omega-3 supplements lowered a blood fat called triglycerides. For heart events and for an eye disease of ageing, they showed little or no benefit.
| Triglycerides (a blood fat) | Omega-3 lowered them |
|---|---|
| Deaths, heart and blood vessel events | Little or no effect |
| Coronary heart disease events | May slightly lower the risk |
| Blood pressure | A slight fall at 2 to 3 g a day in one review; little or no effect in another |
| Memory and thinking | No change in healthy older adults or in Alzheimer's disease |
| Eyes (macular degeneration) | Did not lower the risk of advanced disease or loss of sight |
| Joints (rheumatoid arthritis) | May ease symptoms beside prescribed medicines; needs more research |
| Mood (major depression) | A small effect, probably too small to matter |
Blood fats (triglycerides)
Fish oil contains the 2 omega-3s called EPA and DHA. A 2020 review by Cochrane, a group that reviews medical trials, pooled 86 trials of omega-3, with 162,796 people. Most of the EPA and DHA trials gave capsules. In these trials, EPA and DHA lowered triglycerides by about 15%. The reviewers rated this evidence high.[1] That change shows up in a blood test. Heart attacks and deaths were counted separately.
In trials, prescription omega-3 at 4 g a day lowered high triglycerides, the NIH (US National Institutes of Health) fact sheet reports.[2] A typical fish oil capsule holds about 180 mg of EPA and 120 mg of DHA, though amounts vary widely.[2]
If your triglycerides are high, your doctor decides the treatment.
Heart events
The same Cochrane review counted deaths and heart and blood vessel events. Taking extra EPA and DHA had little or no effect on them. The reviewers rated this evidence high.
It also counted a narrower group: deaths and events from coronary heart disease alone. Taking extra EPA and DHA may slightly lower this risk. The reviewers rated this evidence low.[1]
The NIH fact sheet says the evidence for a benefit is stronger in people who already have coronary heart disease. It is weaker in healthy people. The American Heart Association does not recommend omega-3 supplements for people without a high risk of heart disease.[2] If you have heart disease, ask your heart doctor first. A capsule does not replace your heart medicines.
Blood pressure
A 2022 review pooled 71 trials with 4,973 people. Doses of 2 to 3 g of EPA and DHA a day lowered blood pressure slightly. The fall was larger in people with high blood pressure, in people with high blood fats, and in older people.[3] The 2020 Cochrane review found little or no effect on blood pressure.[1] If your blood pressure is high, your doctor decides the treatment.
Higher doses and heart rhythm
A 2026 review looked at heart rhythm in trials of EPA and DHA. In people at high heart risk, more than 1.5 g a day was linked to a higher risk of an irregular heartbeat (atrial fibrillation).[4] The 2 to 3 g a day in the blood pressure trials is more than 1.5 g. Our article on whether omega-3 is safe covers higher amounts.
Memory, eyes, joints and mood
Memory and thinking. In healthy older adults and in people with Alzheimer's disease, supplements did not change memory and thinking compared with a dummy pill. In people with mild memory problems, omega-3s may improve attention, processing speed and immediate recall. More trials need to confirm this.[2]
Eyes. In people with age-related macular degeneration (an eye disease), up to 5 years of supplements did not lower the risk that the disease became advanced. They did not lower the risk of moderate or severe loss of sight either. The NIH says the evidence so far shows no consistent link between omega-3s and dry eye.[2]
Joints. For rheumatoid arthritis, omega-3s may ease symptoms when added to the medicines a doctor prescribes. More research needs to confirm this.[2]
Mood. A 2021 Cochrane review of 33 trials looked at adults with major depression. The authors found a small effect on symptoms, probably too small to matter in treatment. They rated the evidence very low.[5]
Talk to your doctor
Your doctor knows your blood tests and your heart history. Ask which of these findings apply to you. If you are pregnant, our article on omega-3 in pregnancy covers what trials found and what to ask at your antenatal visit.
Ask your doctor before you take an omega-3 supplement if you take a blood thinner or any medicine regularly, are pregnant or breastfeeding, or are buying it for a child.
If you have a fish or shellfish allergy, ask your doctor before you take fish or krill oil.
Do not take more than the pack says.
Do not stop or cut down a medicine your doctor prescribed and take a supplement instead.
Medical disclaimer: This article is general information. It does not replace advice from your doctor about your own health.
Common questions
Yes. In trials, the omega-3s in fish oil (EPA and DHA) lowered triglycerides, a fat in the blood. If your triglycerides are high, your doctor decides the treatment.
In a 2020 Cochrane review, taking extra EPA and DHA, the omega-3s in fish oil, had little or no effect on deaths and on heart and blood vessel events. Most of its EPA and DHA trials gave capsules.
Trials found no effect in healthy older adults or in people with Alzheimer's disease. For mild memory problems, more trials are needed.
Sources
- Abdelhamid AS, Brown TJ, Brainard JS, Biswas P, Thorpe GC, Moore HJ, et al. Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database Syst Rev. 2020;3(3):CD003177. doi:10.1002/14651858.CD003177.pub5. PMID: 32114706. Available from: cochrane.orgCited atPlain language summary, Key resultsPlain language summary, Key resultsAbstract, Main results (PubMed 32114706)
- National Institutes of Health, Office of Dietary Supplements. Omega-3 fatty acids: fact sheet for health professionals [Internet]. National Institutes of Health; 2025 Aug 22 [cited 2026 Oct 23]. Available from: ods.od.nih.govCited atOmega-3s and Health, Cardiovascular disease, Recommendations from the American Heart Association; ConclusionsSources of Omega-3s, Dietary supplementsOmega-3s and Health, Cardiovascular disease, Recommendations from the American Heart AssociationOmega-3s and Health, Alzheimer's disease, dementia, and cognitive functionOmega-3s and Health, Age-Related Macular Degeneration; Dry eye diseaseOmega-3s and Health, Other conditions, Rheumatoid arthritis
- Zhang X, Ritonja JA, Zhou N, Chen BE, Li X. Omega-3 polyunsaturated fatty acids intake and blood pressure: a dose-response meta-analysis of randomized controlled trials. J Am Heart Assoc. 2022;11(11):e025071. doi:10.1161/JAHA.121.025071. PMID: 35647665. Available from: pmc.ncbi.nlm.nih.govCited atAbstract, Results
- Abuknesha NR, O'Keefe JH, Qian F, Tintle NL, Lin Y, Sun Y, et al. Effects of omega-3 fatty acid treatment on risk for atrial fibrillation: an updated meta-analysis of 35 trials including 114 592 individuals. Circ Arrhythm Electrophysiol. 2026;19(8):e014785. doi:10.1161/CIRCEP.125.014785. PMID: 42517224. Available from: pubmed.ncbi.nlm.nih.govCited atAbstract, Results and Conclusions
- Appleton KM, Voyias PD, Sallis HM, Dawson S, Ness AR, Churchill R, et al. Omega-3 fatty acids for depression in adults. Cochrane Database Syst Rev. 2021;11(11):CD004692. doi:10.1002/14651858.CD004692.pub5. PMID: 34817851. Available from: pubmed.ncbi.nlm.nih.govCited atAbstract, Main results and Authors' conclusions