Americans spend more than $1 billion each year on fish oil supplements, largely because of claims that the omega-3 fatty acids they contain can support brain health. These important nutrients help create and maintain connections between brain cells that are important for thinking and memory.
But new research from Keck Medicine of the University of Southern California suggests that boosting omega-3 levels through supplements may not provide the brain benefits many people expect. Research published in electronic biomedicinefound that although omega-3s from fish oil successfully reached the brain, they did not improve measures of brain health in older adults at increased risk of Alzheimer’s disease.
In a two-year, placebo-controlled, double-blind clinical trial, researchers found that high-dose omega-3 supplements failed to improve memory, cognitive function, or brain cell loss in regions associated with Alzheimer’s disease.
“We all wish there was a silver bullet for preventing Alzheimer’s disease, but our results showed that fish oil supplements do not appear to protect brain health,” said Hussein Naji Yassin, MD, director of the USC Center for Personalized Brain Health and lead investigator of the study. “Although omega-3s play an important role in forming brain cell connections essential for cognition, our results do not support that fish oil supplementation is a preventive measure against Alzheimer’s disease.”
Fish oil reaches the brain
The study involved 365 adults aged 55 to 80 who rarely consumed fish, a major dietary source of omega-3 fatty acids. The researchers believed that all participants were at increased risk of developing Alzheimer’s disease. Nearly half (47%) carried the APOE4 gene, the strongest known genetic risk factor for late-onset Alzheimer’s disease.
Participants were randomly assigned to receive a daily fish oil supplement or a placebo. 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 get into the brain.
To answer this question, they measured DHA levels in the cerebrospinal fluid surrounding the brain and spinal cord. After six months, DHA levels increased by an average of 17%, confirming that the nutrient had successfully reached its destination.
No memory improvement or brain aging
Although DHA reached the brain, it did not lead to measurable cognitive benefits.
The researchers assessed participants’ memory and thinking abilities at the start of the study and again two years later. Those who took DHA supplements performed no better on cognitive tests than participants who took a placebo.
Brain imaging results told a similar story. The scans showed that fish oil supplements did not slow the shrinkage of the hippocampus, an area of the brain critical for memory that is commonly used as a marker of brain aging and risk of Alzheimer’s disease.
Why didn’t omega-3 help?
The findings prompted researchers to investigate why omega-3s can reach the brain without causing noticeable improvements in brain health.
Based on earlier research, Yassin and colleagues suspect that omega-3s may be more effective when taken as part of an overall Mediterranean-style eating regimen rather than as a stand-alone supplement. The Mediterranean diet is naturally rich in omega-3s and is associated with a lower risk of Alzheimer’s disease.
“We are seeking to better understand how the brain processes omega-3s and whether factors such as poor health, dietary patterns, genetic risk and age may alter the brain’s ability to effectively absorb and use omega-3s,” Yassin said. “We are working to develop drugs that can help the brain better use these nutrients to preserve cognitive function.”
A healthy lifestyle still matters the most
Although lifestyle factors were not directly examined 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.
“Staying healthy throughout the lifespan remains the most powerful tool we have for reducing the risk of Alzheimer’s disease, including regular exercise, quality sleep and a balanced diet,” Yassin said. “A healthy lifestyle for the brain is equivalent to regular car maintenance and quality oil changes. The brain is more likely to lose more function if health problems elsewhere in the body go unaddressed, just as car engines stop working if regular maintenance is missed.”
Other USC study authors include Lina D’Orazio, PhD, a clinical psychologist and neuropsychologist at Keck Medicine; Lon Schneider, PhD, professor of psychiatry and behavioral sciences at the Keck School of Medicine of the University of Southern California; Michael Harrington, MD, professor of research neuroscience at the Keck School; and Meredith Brasky, PhD, assistant professor of neuroscience at the Keck School.