Omega-3s and Brain Health: Fish vs. Fish Oil Pills
Omega-3s and brain health are closely linked because your brain is rich in DHA, an omega-3 fat found mainly in seafood. That has made fish oil one of the best-selling supplements for memory. But when researchers tested fish oil pills in large trials, the results were disappointing. Eating fish tells a different story.
Health note: This article is for general education only. It is not medical advice and it does not replace care from your doctor. Foods and supplements are not a substitute for prescribed treatment. Talk to a licensed health professional before changing your diet, medicines or supplements, especially if you are pregnant, take prescription drugs or have a chronic condition.
- DHA is concentrated in the brain and the retina of the eye.
- Large trials found fish oil pills did not slow cognitive decline in healthy older adults.
- Eating fish about twice a week is linked to better brain aging in observational studies.
Omega-3s and brain health: what large trials found
Mixed evidence
- VITAL: 1 gram a day of omega-3s did not significantly slow cognitive decline over about 5 years in healthy older adults.
- AREDS2: 350 mg DHA plus 650 mg EPA daily for 5 years had no meaningful effect on cognitive function in 3,501 older adults.
At the same time, the NIH notes that some, but not all, studies show people who eat more fish have a lower risk of Alzheimer’s disease and cognitive problems. Fish brings protein, vitamin D, B12 and selenium, and it often replaces less healthy foods on the plate, which may explain part of the difference.
Best fish choices (and mercury)
For most adults, 8 to 12 ounces a week of lower-mercury seafood is a smart target. Good choices include:
- Salmon, sardines, anchovies, herring and trout
- Oysters, shrimp and canned light tuna
- Mackerel (Atlantic or chub, not king mackerel)
Limit high-mercury fish such as shark, swordfish, king mackerel, bigeye tuna and tilefish, especially if you are pregnant.
Plant sources of omega-3
Limited evidence
Walnuts, flaxseed, chia seeds and purslane provide ALA, a plant omega-3. The body converts only a small amount of ALA into DHA, so plant foods are healthy but not a full replacement for seafood. Vegans can ask their doctor about algae-based DHA.
If you take fish oil anyway
- Common side effects: fishy aftertaste, heartburn, nausea and loose stools.
- High doses may increase bleeding time, which matters with blood thinners.
- In people with heart disease, 4 grams a day slightly increased the risk of atrial fibrillation in studies.
- Choose a product with a USP or third-party seal and keep it in a cool place.
More ways to protect your memory
Read our brain-healthy foods and habits guide and our article on vitamin B12 and memory.
The bottom line
The bottom line on omega-3s and brain health: eat fish about twice a week and be skeptical of pills sold for memory. The evidence on omega-3s and brain health favors food over supplements.
Frequently asked questions
How much fish should I eat for brain health?
Most adults can aim for 8 to 12 ounces of lower-mercury seafood a week, which is about two to three servings.
Are canned sardines and salmon as good as fresh?
Yes. Canned salmon and sardines keep their omega-3s, are affordable and often include soft, edible bones that add calcium.
Should I take fish oil if I have a family history of Alzheimer’s?
Large trials have not shown fish oil prevents cognitive decline. Talk with your doctor about your overall risk, blood pressure, activity and diet, which have stronger evidence.
Your next step
Plan two fish meals for next week, for example salmon on Monday and sardines on whole grain toast on Thursday.
Common myths about omega-3s and brain health
- Myth: Fish oil pills prevent dementia. Fact: Large trials such as VITAL and AREDS2 did not show that.
- Myth: Plant omega-3s equal fish omega-3s. Fact: The body turns only a little ALA into DHA.
- Myth: All fish are high in mercury. Fact: Salmon, sardines, trout and shrimp are low in mercury and rich in omega-3s, which makes them great for omega-3s and brain health.
Sources
- NIH Office of Dietary Supplements: Omega-3 Fatty Acids (Health Professional)
- NIH Office of Dietary Supplements: Omega-3 Fatty Acids (Consumer)
About the author: Reginaldo Encarnacao is an independent health writer who researches public sources such as the National Institutes of Health (NIH). He is not a doctor, pharmacist or dietitian.
Medical disclaimer: The information on this page is for educational purposes only and is not intended to diagnose, treat, cure or prevent any disease. Statements about dietary supplements have not been evaluated by the Food and Drug Administration. Individual results vary. See our full disclaimer.
