Alzheimer’s study finds omega-3 supplements fall short of protective benefits

Fish oil supplements successfully delivered omega-3 fatty acids to the brain in older adults at risk for Alzheimer’s disease, but a new study suggests that this was not enough to improve cognitive health.

Fish oil has long been promoted as an easy way to support brain function, based on omega-3 fatty acids that are essential for maintaining brain cell membranes and neural connections. However, new research suggests the relationship between supplementation and brain health is more complex than simply increasing omega-3 intake, as an article by SciTechDaily points out.

Researchers at Keck Medicine of USC found that while high-dose fish oil supplements did raise omega-3 levels in the brain, they did not lead to measurable improvements in memory, cognitive performance, or brain structure among older adults at elevated risk of Alzheimer’s.

The findings, published June 18 in eBioMedicine, suggest scientists may need to better understand how the aging brain processes these nutrients rather than focusing solely on increasing their levels.

“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,” said Hussein Naji Yassine, MD, director of the USC Center for Personalized Brain Health and lead investigator of the study.

“While omega-3s play an important role in forming brain cell connections needed for cognition, our results do not support fish oil supplements as a preventive measure against Alzheimer’s.”

The study involved 365 adults aged 55 to 80 who rarely consumed fish, a key dietary source of omega-3s, and who were considered at elevated risk of Alzheimer’s disease. Nearly half (47%) carried the APOE4 gene, the strongest known genetic risk factor for late-onset Alzheimer’s.

Participants were randomly assigned to receive either daily fish oil supplements or a placebo. The supplements contained 2,000 mg of docosahexaenoic acid (DHA), an omega-3 fatty acid critical for brain function.

Researchers first examined whether the omega-3 from the supplements actually reached the brain. By measuring DHA levels in cerebrospinal fluid, they found that after six months, levels increased by an average of 17%, confirming the nutrient reached its target.

The next stage of the study assessed whether this biological change translated into cognitive benefits. Participants completed memory and cognitive tests at the start of the study and again after two years. Those taking DHA supplements performed no better than those receiving a placebo, and brain scans showed no prevention of shrinkage in the hippocampus, a key memory-related region linked to Alzheimer’s risk.

Yassine and his team are now investigating why omega-3s can reach the brain without producing measurable cognitive benefits. Based on earlier research, they suggest omega-3s may be more effective when consumed as part of a Mediterranean-style diet, rather than as isolated supplements.

Although the study did not examine broader lifestyle factors, the researchers emphasized that long-term brain health likely depends on overall healthy habits rather than fish oil supplementation alone.

By Nazrin Sadigova