Americans spend more than $1 billion each year on fish oil supplements, largely due to claims that the omega-3 fatty acids found in fish oil can support brain health. These essential nutrients help build and maintain connections between brain cells that are important for thinking and memory.
But a new study from Keck Medicine at the University of Southern California suggests that increasing omega-3 levels through supplements may not have the brain benefits many people expect. This research e-biomedicinefound that although omega-3 from fish oil was successful in reaching the brain, it was not effective in improving brain health in older adults at high risk of Alzheimer’s disease.
Over the course of a two-year, double-blind, placebo-controlled clinical trial, researchers found that high-dose omega-3 supplements failed to improve memory, cognitive performance, or brain cell loss in areas associated with Alzheimer’s disease.
“While we all wish there was a magic bullet to prevent Alzheimer’s disease, our findings show that fish oil supplements do not appear to be effective in protecting brain health,” said Hussein Naji Yassin, M.D., director of the USC Center for Personalized Brain Health and principal investigator of the study. “Omega-3s play an important role in forming brain cell connections needed for cognition, but our findings do not support fish oil supplements as a preventive measure against Alzheimer’s disease.”
fish oil reaches the brain
The study involved 365 adults between the ages of 55 and 80 who consumed little fish, which is a major dietary source of omega-3 fatty acids. Researchers considered all participants to be at high risk for Alzheimer’s disease. Almost half (47%) had the APOE4 gene, the strongest known genetic risk factor for late-onset Alzheimer’s disease.
Participants were randomly assigned to receive either a fish oil supplement or a placebo daily. Each supplement contained 2,000 mg of docosahexaenoic acid (DHA), an omega-3 fatty acid that plays an important role in brain function.
One of the researchers’ first goals was to determine whether DHA from supplements could actually reach the brain.
To answer that question, they measured DHA levels in the cerebrospinal fluid that surrounds the brain and spinal cord. After 6 months, DHA levels increased by an average of 17%, confirming that the nutrients successfully reached their intended destinations.
Memory and brain aging are not improved
Although DHA reached the brain, it did not lead to measurable cognitive effects.
Researchers assessed participants’ memory and thinking skills at the beginning of the study and again two years later. Participants who took DHA supplements performed worse on cognitive tests than those who took a placebo.
Similar results were found from brain imaging tests. The scans showed that fish oil supplements do not slow down the shrinkage of the hippocampus, a brain region important for memory that is commonly used as a marker of brain aging and Alzheimer’s disease risk.
Why didn’t omega-3 help?
This discovery led researchers to investigate why omega-3s are able to reach the brain without producing any noticeable improvements in brain health.
Based on previous research, Yassin and his colleagues believe that omega-3s may be more effective when taken as part of an overall Mediterranean-style dietary pattern, rather than as a standalone supplement. The Mediterranean diet is naturally rich in omega-3s and is associated with a lower risk of Alzheimer’s disease.
“We are focused on better understanding how the brain processes omega-3s and whether factors such as poor health, dietary patterns, genetic risk, and age can alter the brain’s ability to effectively absorb and utilize omega-3s,” Yassin said. “We are working to develop drugs that may help the brain better utilize these nutrients to maintain cognitive function.”
Healthy living is still the most important
Although lifestyle factors were not directly investigated in this study, the researchers emphasize that maintaining overall health remains one of the most effective ways to support brain function and reduce the risk of Alzheimer’s disease.
“Maintaining good health throughout life remains the most powerful tool for reducing Alzheimer’s disease risk, including regular exercise, quality sleep, and a balanced diet,” Yassin said. “Living a healthy lifestyle is the brain equivalent of regular car maintenance and high-quality oil changes. Just as a car’s engine stalls if you don’t do regular maintenance, your brain is more likely to lose function if health issues in other parts of your body are not addressed.”
Other USC authors on the study include Dr. Lina D’Orazio, a clinical psychologist and neuropsychology expert at Keck Medicine; Dr. Ron Schneider, Professor of Psychiatry and Behavioral Sciences at the Keck School of Medicine of the University of Southern California. Michael Harrington, MD, research professor of neurology at the Keck School. and Dr. Meredith Blaskey, assistant professor of neurology at the Keck School.
