Millions of people take fish oil supplements in hopes of protecting their brains, but recent research indicates these supplements may not prevent Alzheimer’s disease.
Supplements reached the brain—but showed no benefit
A team at the University of Southern California’s Keck School of Medicine discovered that high doses of DHA, an omega-3 fatty acid essential for brain function, entered the brains of older adults at risk for dementia. After two years, the supplements did not improve memory, thinking skills, or protect against changes in brain structure associated with aging and Alzheimer’s.
Nearly half of the 365 participants had APOE4, the strongest genetic risk factor for late-onset Alzheimer’s. All were cognitively healthy at the start but rarely ate fish, a primary source of omega-3s in the diet.
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The trial followed a randomized, double-blind, placebo-controlled design. Participants received either 2,000 milligrams of DHA daily or a placebo. Neither the participants nor the investigators knew who received which treatment.
DHA levels in cerebrospinal fluid increased by 17% after six months for those taking the supplement, proving the capsules delivered the nutrient to the brain. Cognitive tests and brain scans, however, revealed no difference between the groups. The hippocampus, a region critical for memory, shrank at the same rate in both.
Findings contradict earlier expectations
“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, the study’s lead author and director of the USC Center for Personalized Brain Health.
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Yassine explained that while omega-3s play an important role in forming brain cell connections needed for cognition, the high-dose supplements in this trial produced no measurable benefits. The outcome challenges one common explanation for the disappointing results of earlier fish oil studies: perhaps the omega-3s were simply not reaching the brain. In this trial, they clearly did—yet, there was still no measurable cognitive benefit.
Omega-3s remain important. DHA is a critical component of brain cell membranes and plays a role in the connections brain cells use to communicate. The unanswered question is why increasing DHA levels through a high-dose supplement did not produce better results.
Whole foods may offer advantages over supplements
The study included adults who rarely ate fish, one of the richest dietary sources of omega-3 fatty acids. The team noted that nutrients from food might work differently than those isolated in pills. The search for an effective Alzheimer’s prevention strategy remains ongoing.
