Fish oil supplements show little benefit for preventing Alzheimer’s disease

Americans spend more than $1 billion annually on fish oil supplements, in part due to purported cognitive benefits from the omega-3 fatty acids they contain, essential nutrients that help form brain cell connections needed for cognition.

However, a new study from Keck Medicine of USC published today in Biomedicine It suggests that increasing omega-3 levels via supplements has little effect on brain health despite evidence that the nutrients reach the brain directly.

The two-year, double-blind, placebo-controlled study of older adults with a high risk of developing Alzheimer’s disease showed that high doses of omega-3 did not improve memory, cognitive function, or brain cell loss in areas of the brain associated with Alzheimer’s disease.

We all wish there was a magic solution to preventing Alzheimer’s disease, but our findings showed that fish oil supplements do not appear to protect brain health. “While omega-3 fatty acids play an important role in forming brain cell connections needed for cognition, our results do not support fish oil supplements as a preventative measure against Alzheimer’s disease.”

Hussein Naji Yassin, MD, director of the USC Center for Personalized Brain Health and the study’s principal investigator

How was the study conducted?

The researchers recruited 365 adults, ages 55 to 80, who rarely ate omega-3-rich fish and who the authors studied were considered to be at risk for developing Alzheimer’s disease. About half (47%) carry the APOE4 gene, the strongest genetic risk factor for late-onset Alzheimer’s disease. Participants were randomly assigned to receive either daily fish oil supplements or a placebo. The supplements contain 2,000 mg of docosahexaenoic acid (DHA), one of the main omega-3 fatty acids involved in brain function.

The researchers were first interested in knowing whether the omega-3s in the supplements were able to reach the brain.

They measured DHA levels in the cerebrospinal fluid that surrounds the brain, and found an average 17% increase in DHA levels in patients’ brains after six months, confirming that omega-3 had reached its intended target.

Next, the researchers tested the participants’ memory and cognitive abilities at the beginning of the study and again two years later. Study participants who took DHA supplements did no better on tests than those who took a placebo. Brain scans also showed that the supplements did not prevent shrinkage of the hippocampus, a brain region important for memory that is often used as a marker of brain aging and risk of Alzheimer’s disease.

Now, Yassin and his team are focused on solving why omega-3 supplements reach the brain without affecting brain health. Based on their previous research, they believe Omega-3 may work better as part of a Mediterranean-style diet, which is naturally rich in Omega-3 and is associated with a lower risk of Alzheimer’s disease, than a stand-alone supplement.

“We are focused on better understanding how the brain processes omega-3s and whether factors, such as poor health, dietary pattern, genetic risk, and age, may alter the brain’s ability to absorb and use omega-3s effectively,” Yassin said. “We are working to develop medications that may help the brain better utilize these nutrients to maintain cognitive function.”

A holistic lifestyle remains the best means of prevention

Although the researchers are outside the scope of the study, they stress that healthy living in general – rather than relying on fish oil supplements alone – is the best way to protect brain health.

“Staying healthy throughout life remains our most powerful tool for reducing the risk of Alzheimer’s disease, including regular exercise, good sleep and a balanced diet,” Yassin said. “Living a healthy lifestyle is the brain equivalent of getting regular car maintenance and a high-quality oil change. The brain is likely to lose greater function if health problems in other parts of the body remain unaddressed, in the same way that car engines stop working if regular maintenance is skipped.”

Other USC study authors include Lina Dorazio, Ph.D., a clinical psychologist and neuropsychologist at Keck Medicine; Lon Schneider, Ph.D., Professor Psychiatry and behavioral sciences at the Keck School of Medicine of the University of Southern California; Michael Harrington, MD, PhD, research professor of neuroscience at the Keck School; and Meredith Brasky, Ph.D., assistant professor of neuroscience at the Keck School.