“We are working to develop medications that may help the brain better utilize these nutrients to preserve cognitive function.” That is where Hussein Naji Yassine says his lab is heading after a two-year trial found fish oil did nothing for the memory of older adults at risk of Alzheimer’s.
Yassine directs the USC Center for Personalized Brain Health and led the study, run by Keck Medicine of USC and published June 19, 2026 in eBioMedicine. The result itself was blunt. High doses of omega-3s did not improve memory, cognitive performance or brain cell loss in regions tied to the disease.
A negative result with a twist
The twist is that the supplement worked, at least in one sense. Researchers measured DHA in cerebrospinal fluid and found an average 17 percent rise after six months. The nutrient reached the brain. It just did not change how the brain performed.
The trial enrolled 365 adults aged 55 to 80 who rarely ate fish. About 47 percent carried the APOE4 gene, the strongest known genetic risk factor for late-onset Alzheimer’s. In the placebo-controlled, double-blinded design, participants received either a daily supplement of 2,000 mg of DHA or a placebo.
At the two-year mark, the DHA group scored no better on memory and thinking tests. Imaging showed the supplement did not slow shrinkage of the hippocampus, the memory region that serves as a marker of brain aging and Alzheimer’s risk.
“We all wish there was a silver bullet for preventing Alzheimer’s, but our findings showed that fish oil supplements do not appear to protect brain health,” Yassine said.
What the team is chasing now
The group wants to know why the omega-3s arrive without effect. Yassine said the lab is looking at “whether factors, such as poor health, dietary pattern, genetic risk and age, may change the brain’s ability to effectively absorb and use omega-3s.”
One idea comes from the team’s earlier work. They suspect omega-3s perform better as part of a Mediterranean-style diet than as a standalone supplement.
Lifestyle was not measured in this trial. Still, the researchers say overall healthy living is the best protection for the brain. “Staying healthy throughout life remains the most powerful tool we have for reducing Alzheimer’s risk, including regular exercise, quality sleep and a balanced diet,” Yassine said.
Other USC authors are Lina D’Orazio, Lon Schneider, Michael Harrington and Meredith Braskie. The National Institutes of Health and the Alzheimer’s Drug Discovery Foundation supported the research. As always with supplements, ask your doctor.
Sources
- Millions take omega-3 fish oil for brain health but a new study found no benefit
- Fish oil supplements may not prevent Alzheimer’s-related decline
