Study Finds Fish Oil Supplements May Not Improve Brain Health in Older Adults
Americans spend more than $1 billion annually on fish oil supplements, often based on claims that omega-3 fatty acids support brain health. Omega-3s, including docosahexaenoic acid, or DHA, are essential nutrients involved in maintaining connections between brain cells that support memory and thinking.
A new study from Keck Medicine of USC, published in eBioMedicine, found that high-dose fish oil supplements did not improve cognitive outcomes in older adults considered at increased risk for Alzheimer’s disease. The two-year clinical trial was placebo-controlled and double-blinded.
The study included 365 adults ages 55 to 80 who rarely ate fish. Nearly half of the participants carried the APOE4 gene, the strongest known genetic risk factor for late-onset Alzheimer’s disease. Participants were randomly assigned to receive either a daily fish oil supplement containing 2,000 milligrams of DHA or a placebo.
Researchers first examined whether DHA from supplements reached the brain. After six months, DHA levels in cerebrospinal fluid increased by an average of 17%, indicating that the omega-3 fatty acid had entered the central nervous system.
However, this increase did not lead to measurable benefits. After two years, participants who took DHA supplements performed no better on memory and thinking tests than those who received the placebo. Brain imaging also showed no reduction in shrinkage of the hippocampus, a region associated with memory and Alzheimer’s risk.
Lead investigator Hussein Naji Yassine said the findings do not support fish oil supplements as a preventive measure against Alzheimer’s disease. Researchers are now exploring why omega-3s may reach the brain without producing cognitive improvements.
The study authors noted that omega-3s may have different effects when consumed as part of a broader dietary pattern, such as a Mediterranean-style diet. They also emphasized that regular exercise, adequate sleep, balanced nutrition and management of overall health remain important factors in supporting brain function.