Americans spend more than $1 billion a year on fish oil supplements, often because of claims that the omega-3 fatty acids they contain may help protect memory and support brain health.
Omega-3s are essential nutrients that play an important role in building and maintaining connections between brain cells. Those connections are crucial for thinking, learning and memory.
However, new research from Keck Medicine of USC suggests that raising omega-3 levels through fish oil supplements may not deliver the protective effects many consumers expect.
The study, published in eBioMedicine, found that although omega-3 fatty acids from supplements successfully reached the brain, they did not improve memory, cognitive performance, or other measures of brain health in older adults at increased risk of Alzheimer’s disease.
The findings came from a two-year, double-blind, placebo-controlled clinical trial involving 365 adults aged 55 to 80. Participants rarely ate fish, one of the main dietary sources of omega-3 fatty acids, and were considered at elevated risk of developing Alzheimer’s.
Nearly half of the participants, 47%, carried the APOE4 gene, which is regarded as the strongest known genetic risk factor for late-onset Alzheimer’s disease.
Participants were randomly assigned to receive either a daily Fish oil supplement or a placebo. Each supplement contained 2,000 milligrams of docosahexaenoic acid, or DHA, an omega-3 fatty acid that supports normal brain function.
Researchers first wanted to determine whether DHA from the supplements could cross the blood-brain barrier. To test this, they measured DHA levels in cerebrospinal fluid, the liquid that surrounds the brain and spinal cord. After six months, DHA levels had risen by an average of 17%, showing that the nutrient had reached the brain.
Despite that increase, researchers found no measurable improvement in memory or thinking abilities. Participants completed cognitive tests at the beginning of the trial and again two years later. Those who received DHA supplements performed no better than those who received a placebo.
Brain scans produced similar results. The supplements did not slow shrinkage of the hippocampus, a region of the brain closely linked to memory and commonly used as a marker of brain aging and Alzheimer’s risk.
“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.” Researchers are now trying to understand why omega-3s can reach the brain without producing noticeable cognitive benefits.
Yassine and his colleagues believe the nutrients may be more effective when consumed as part of a broader Mediterranean-style diet rather than as a standalone supplement. The Mediterranean diet naturally contains omega-3-rich foods and has been associated with a lower risk of Alzheimer’s disease.
“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 the study did not directly examine lifestyle habits, researchers said overall health remains one of the most important factors in supporting brain function and reducing Alzheimer’s risk.
“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,” said Yassine. “Living a healthy lifestyle is the brain’s equivalent of getting regular car maintenance and high-quality oil changes.
The brain is more likely to lose greater function if health issues in other parts of the body go unaddressed, in the same way that car engines stop working if regular maintenance is skipped.” Other USC researchers involved in the study included Lina D’Orazio, PhD; Lon Schneider, PhD; Michael Harrington, MD; and Meredith Braskie, PhD.
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Materials provided by the University of Southern California – Health Sciences. Note: Content may be edited for style and length.