Omega-3 supplements, long touted for brain health, showed no benefit for memory or thinking in a new clinical trial from the University of Southern California.
The two-year study found that high doses of DHA, a key omega-3 fatty acid, did not slow brain cell loss or improve cognition in older adults at risk for dementia, even though the supplement raised omega-3 levels in the blood and brain.
USC Study Finds Omega-3 Supplements Do Not Improve Cognition
“Omega-3 supplements as a blunt instrument do not work,” said lead study author Dr. Hussein Yassine, the Volke Endowed Professor of Neurology at USC’s Keck School of Medicine. “Even when we saw high levels of omega-3 in the brains of the treatment group, it did not improve cognition.”
Yassine directs Keck’s Center for Personalized Brain Health. The results were published Thursday, June 18, in the journal eBioMedicine, part of The Lancet family.
Researchers tracked 365 people ages 55 to 80 who had low omega-3 levels and at least one dementia risk factor, such as obesity, high blood pressure, high cholesterol or a sedentary lifestyle.
Omega-3 Levels Rose Significantly but Memory Did Not Improve
Nearly half carried at least one copy of the APOE4 gene, which raises Alzheimer’s risk and can make it harder for the brain to process fats.
Half the group got 2,000 milligrams of DHA a day from an algae supplement. The other half received a placebo. Everyone took a vitamin B complex, too.
The research was randomized, double-blind, and placebo-controlled, the gold standard for this type of research.
Blood tests showed omega-3 levels in red blood cells jumped from about 4.9% to 11% in the supplement group.
DHA in the cerebrospinal fluid around the brain rose by an average of 17% after six months. The increases were observed in people with the APOE4 gene as well.
But MRIs and cognitive tests reported a different story: there was no difference in memory, thinking skills, or the size of the hippocampus, the brain’s memory center, between the two groups after 24 months.
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Yassine said the findings challenge years of messaging that fish oil or algae pills can help protect against dementia, as he pointed to lifestyle instead.
In Mediterranean regions where people eat plenty of fatty fish, exercise, manage stress, and stay socially connected, higher omega-3 levels are associated with better brain health.
But popping supplements on a typical Western diet of fast food and little activity does not deliver the same results, he said.
“What does work? Optimizing your health with exercise, stress reduction, quality sleep and a plant-based diet while adding omega-3s from fatty fish, nuts and seeds,” Yassine said.
Dr. Richard Isaacson’s Take
CNN reports that Dr. Richard Isaacson, an Alzheimer’s prevention researcher not involved in the study, agreed that omega-3s matter for brain health, especially for APOE4 carriers. But he said the supplements only help when people already follow healthy habits.
“If they have an unhealthy lifestyle like the population in this study, an omega-3 supplement just isn’t going to work,” Isaacson said.
The Global Organization for EPA and DHA Omega-3s pushed back, saying the study should be viewed alongside broader research.
The group pointed to reviews showing potential benefits for Alzheimer’s progression and noted thousands of studies on omega-3s overall.
Omega-3 fatty acids are important for the body because they maintain heart health, reduce inflammation and make up a big part of brain tissue.
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The body cannot make them, so they must come from food like salmon, sardines, walnuts or seeds, or from supplements.
Many Americans fall short in their intake of fatty fish, which is why supplements have become popular. DHA supports brain structure while EPA helps with inflammation. Algae versions offer a vegan alternative.
Yassine stated that whole foods bring extra benefits supplements cannot match. A few walnuts or some wild salmon will also give you the omega-3s, but in addition to nutrients, proteins, and minerals. However, he notes that frying fish or pairing it with junk food can undo some of those gains.
The study adds to questions about using supplements as a simple fix for complex problems like dementia risk. Earlier trials with lower doses also struggled to show clear brain benefits.
Yassine said his team hopes the results push people toward real lifestyle changes rather than relying on pills alone.
