Study finds fish oil boosts brain omega-3s but not memory

A two-year study of 365 adults ages 55 to 80 found that fish oil delivered omega-3s to the brain, but it did not improve memory, cognitive test scores or Alzheimer’s-related brain changes.

Participants in the placebo-controlled, double-blind trial rarely ate fish and were considered at elevated risk for Alzheimer’s disease. About 47% carried APOE4, the strongest genetic risk factor for late-onset Alzheimer’s disease. They were assigned to receive either placebo or 2,000 mg a day of DHA, a key omega-3 fatty acid.

The supplement did raise brain DHA levels, which increased by an average of 17% after six months. But after two years, the DHA group did no better than placebo on memory and cognitive testing, and MRI scans showed no prevention of hippocampal shrinkage, the kind of brain atrophy often tied to Alzheimer’s progression. The study was published in eBioMedicine.

Hussein Naji Yassine of the USC Center for Personalized Brain Health led the work. Omega-3s may work better as part of a Mediterranean-style dietary pattern than as a stand-alone pill.

Americans spend more than $1 billion a year on fish oil supplements, much of it driven by marketing that links omega-3s to memory, longevity and brain protection.

A 2024 Oregon Health & Science University study of 102 adults age 75 and older found no statistically significant overall benefit, although APOE4 carriers showed signs of reduced nerve-cell breakdown. No single food, ingredient, vitamin or supplement has been proven to prevent, treat or cure Alzheimer’s disease.