The short answer: for most people, fish oil isn’t worth taking for memory or general heart protection. A two-year trial published in 2026 found high-dose DHA reached the brain but didn’t improve memory or protect against brain shrinkage. A review of 86 trials found little or no effect on deaths, heart events or stroke. Fish oil does lower triglycerides, by about 15%. Eating oily fish once a week is the better first step.
That’s not to say omega-3 fats don’t matter. They do. The question is whether a capsule gives you what the food does, and so far it mostly doesn’t.
Does fish oil help your memory?
The newest and best-designed test says no. Researchers at the University of Southern California ran a randomized, double-blind trial with 365 adults aged 55 to 80 who rarely ate fish and were at raised risk of Alzheimer’s. Nearly half (47%) carried the APOE4 gene variant.
For two years, they took 2,000 mg of DHA, a key omega-3, or a placebo. The capsules did their job: DHA in the fluid around the brain rose 17%, and the omega-3 level in red blood cells more than doubled, from 4.9% to 11%. Even so, there was no difference from placebo in brain volume or thinking skills.
“Our results do not support fish oil supplements as a preventive measure against Alzheimer’s,” said lead investigator Dr. Hussein Yassine.
There’s one caution: 38% of participants dropped out, mainly because of COVID-19. It was also a mid-stage trial built mainly to test whether DHA reaches the brain, so memory wasn’t its main measure. It’s good evidence, not the last word.
Does fish oil protect your heart?
Hardly at all for most people. The largest review, from Cochrane in 2020, covered 86 trials and 162,796 people, mostly taking capsules.
| Outcome | What the review found |
|---|---|
| Death from any cause | Little or no effect |
| Heart and circulation events | Little or no effect |
| Stroke | Little or no effect |
| Irregular heartbeat | Little or no effect (low certainty) |
| Coronary heart disease events | Slight drop: 167 people must take it for one to benefit |
| Triglycerides | Down about 15% |
Harvard reaches a similar view: eating fatty fish weekly is strongly supported, but many large trials haven’t found the same protection from supplements.
Are there risks with fish oil?
The main one is an irregular heartbeat at high doses. A 2026 review of 35 trials and 114,592 people looked at atrial fibrillation:
- High dose in people at high heart risk: EPA and DHA above 1,500 mg a day raised the odds by 43%. In real terms, that’s an extra 0.8 percentage points.
- All other groups, including lower doses: no significant increase.
If you take a blood thinner or have an irregular heartbeat, speak to your doctor before starting or continuing fish oil. Don’t stop a prescribed omega-3 medicine without asking them first.
Who might still benefit from fish oil?
- People with high triglycerides. This is the clearest effect, but it should be managed with your doctor, who may prescribe a specific product.
- People with coronary heart disease risk, where the benefit is small, again on medical advice.
If you don’t eat fish, a low-dose supplement may be a reasonable personal choice. Just don’t expect it to protect your memory.
Is eating fish better than taking fish oil?
The evidence leans that way. The USC researchers suspect food may offer something supplements can’t. The NHS advises at least 2 portions of fish a week, including 1 of oily fish such as salmon or sardines. The advice may differ if you’re pregnant, breastfeeding or feeding children.
Fish brings protein too. An easy way to start is our sheet-pan salmon. Pair it with high-fiber foods such as beans, and you’re most of the way to a heart-friendly dinner. For the wider picture, see how to lower blood pressure.
Should you stop taking fish oil?
If your doctor prescribed it, keep taking it and bring the question to them. If you bought it yourself to protect your memory or your heart, the evidence gives you a good reason to stop paying for it, and to put the money toward fish and walking shoes instead. It’s the same story as many other supplements, so check before you buy: see what the evidence says about magnesium glycinate and creatine.
Protein first, supplements second
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Quick questions
Does fish oil prevent Alzheimer’s?
The evidence so far says no. A two-year trial of high-dose DHA in people at raised risk found no benefit for memory or brain size, even though the DHA reached the brain. Trials in people who already had Alzheimer’s were also negative.
How much fish oil is too much?
There’s no single safe number for everyone. A 2026 review found a higher risk of atrial fibrillation with more than 1,500 mg a day of EPA and DHA in people at high heart risk. Check with your doctor before taking a high dose.
Does fish oil lower triglycerides?
Yes. This is its best-established effect: about a 15% reduction in the Cochrane review, and more with higher doses. If your triglycerides are high, your doctor can tell you if a prescription product makes sense.
Is it OK to take fish oil every day?
For most people it isn’t dangerous at ordinary doses, but it may not do much. The review found little or no effect on serious side effects. Talk to your doctor if you take a blood thinner or have an irregular heartbeat.
What can I eat instead of taking fish oil?
Oily fish such as salmon and sardines. The NHS suggests at least 2 portions of fish a week, including 1 oily. Walnuts and flaxseed contain a plant omega-3 called ALA, which slightly reduced heart events in the Cochrane review.
This article is general information, not medical advice. Don’t stop a prescribed medicine or start a supplement that may interact with one without talking to your doctor.
Sources
- Yassine HN et al. CNS target engagement of high-dose DHA supplementation in older adults at risk for dementia. eBioMedicine, 2026
- ScienceDaily: Millions take fish oil for brain health. A two-year study found no benefit (Oct 2026)
- Abdelhamid AS et al. Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database Syst Rev, 2020
- Effects of Omega-3 Fatty Acid Treatment on Risk for Atrial Fibrillation: An Updated Meta-Analysis of 35 Trials. Circ Arrhythm Electrophysiol, 2026
- Harvard T.H. Chan School of Public Health: Omega-3 Fatty Acids
- NHS: Fish and shellfish