By SmashMeals Editorial · Published · Updated
Fish oil is one of the best-selling supplements in America. Many people take it for their heart or their brain. In October 2026, a carefully designed two-year trial found high-dose fish oil did not protect memory in older adults at risk for Alzheimer's. Here is what the research says about omega-3s, the difference between eating fish and taking pills, and how to get enough from food.
This guide is general information, not medical advice. Talk with your clinician before starting or stopping supplements, especially if you take blood thinners.
The new trial
Researchers at Keck Medicine of USC gave 365 adults aged 55 to 80, who rarely ate fish and were at higher Alzheimer's risk, either 2,000 mg of DHA daily or a placebo for two years. Results were published in eBioMedicine.
- DHA in spinal fluid rose 17% at six months, so the supplement reached the brain.
- Memory and thinking scores were no better than placebo at two years.
- The supplement did not prevent shrinkage of the hippocampus, a memory region.
Lead researcher Hussein N. Yassine, MD, said "our results do not support fish oil supplements as a preventive measure against Alzheimer's," according to ScienceDaily. Read our news coverage.
What omega-3s are
| Type | Main food sources |
|---|---|
| EPA and DHA | Salmon, mackerel, tuna, herring, sardines; also algal oil |
| ALA | Flaxseed, chia seeds, walnuts, canola and soybean oils |
According to the NIH Office of Dietary Supplements, most Americans get enough ALA from food. Recommended amounts for EPA and DHA have not been set.
Fish versus fish oil: what the evidence says
| Question | Eating fish | Fish oil supplements |
|---|---|---|
| Heart | Linked with heart benefits as part of a healthy diet | Lower triglycerides; AHA does not recommend them for people without high cardiovascular risk |
| Brain and dementia | Some, not all, research links fish with lower risk; more study needed | The 2026 USC trial found no memory benefit in at-risk older adults |
| Other nutrients | Protein, vitamin D, selenium, iodine | Omega-3s only |
The American Heart Association suggests one to two seafood servings a week, and about 1 gram a day of EPA plus DHA for people with heart disease, preferably from food, according to the NIH fact sheet.
Why a pill may not equal a plate
The USC researchers suspect diet context, genetics, age and overall health may affect how the brain uses omega-3s. That has not been tested. It fits a pattern seen across nutrition research: nutrients often work differently in whole foods than in isolated pills. An October 2026 study linked 10 different healthy diets with slower biological aging; our guide, no single best diet, explains what they share.
Safety notes
- The FDA advises no more than 5 grams a day of combined EPA and DHA from supplements.
- Common side effects include an unpleasant taste, heartburn, nausea and diarrhea.
- High doses can raise bleeding risk with warfarin and may interact with other medicines.
Getting omega-3s from food
- Aim for fatty fish twice a week: salmon, sardines, trout or mackerel.
- Canned counts. Canned salmon and sardines are affordable and shelf-stable.
- Add ALA foods: ground flaxseed in oatmeal, chia in yogurt, walnuts on salads.
- If you do not eat fish, ask your clinician about algal oil.
- Bake, grill or broil rather than deep-fry.
For people who eat gluten-free, plain fish is naturally gluten-free, but breaded and battered fish usually are not, and fried fish may share a fryer. Our guide to eating out with celiac disease covers shared fryers.
Real food, cooked for you
SmashMeals cooks portioned meals with fish, lean proteins and vegetables in a dedicated gluten-free kitchen in Kingsport, Tennessee, and posts nutrition for each one. See our heart-healthy meals, or order this week's meals.
Sources
Frequently asked questions
- Is it better to eat fish or take fish oil?
- Eating fish provides omega-3s plus protein and other nutrients and is linked with heart benefits. A 2026 trial found high-dose fish oil did not protect memory in at-risk older adults.
- How much fish should I eat?
- The American Heart Association suggests one to two seafood servings a week, according to the NIH Office of Dietary Supplements.
- Is fish oil safe?
- The FDA advises no more than 5 grams a day of combined EPA and DHA from supplements. High doses can raise bleeding risk with warfarin; ask your clinician.