Omega-3 fish oil supplements, long promoted as a way to boost brain health and cognitive function, have been found to have little to no measurable effect on protecting the brain, according to a new study from Keck Medicine of the University of Southern California.
The two-year, placebo-controlled, double-blinded trial followed 365 older adults aged 55 to 80 who were at elevated risk of developing Alzheimer's disease. Participants rarely ate fish, a natural source of omega-3 fatty acids, and nearly half (47%) carried the APOE4 gene, the strongest known genetic risk factor for late-onset Alzheimer's.
No Improvement in Memory or Cognitive Performance
Researchers found that high doses of omega-3s did not improve memory, cognitive performance, or prevent brain cell loss in regions associated with Alzheimer's disease. Participants were randomly assigned to receive either daily fish oil supplements containing 2,000 mg of docosahexaenoic acid (DHA) or a placebo.
While DHA levels in cerebrospinal fluid increased by an average of 17% after six months, confirming the nutrient reached the brain, cognitive tests after two years showed no difference between the supplement and placebo groups. Brain scans also revealed no reduction in shrinkage of the hippocampus, a memory-related region used as an indicator of Alzheimer's progression.
Researchers Urge Caution on Supplement Expectations
“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. “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 researchers are now investigating why omega-3s reach the brain without producing benefits. They suggest omega-3s may be more effective when consumed as part of a Mediterranean-style diet, which is naturally rich in these fatty acids and linked to lower Alzheimer's rates.
Lifestyle Factors Remain Key
“We’re focused on better understanding how the brain processes omega-3s and 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,” said Yassine. “We are working to develop medications that may help the brain better utilize these nutrients to preserve cognitive function.”
Although outside the scope of the study, the researchers emphasize that overall lifestyle factors remain the most effective way to support brain health. “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 added. “Living a healthy lifestyle is the brain’s equivalent of getting regular car maintenance and high-quality oil changes.”
Other authors on the study include Lina D’Orazio, PhD; Lon Schneider, PhD; Michael Harrington, MD; and Meredith Braskie, PhD, all from the University of Southern California’s Keck School of Medicine.
