Two-Year Clinical Trial Finds Fish Oil Supplements Do Not Protect the Brain Against Alzheimer's
A rigorous two-year trial by University of Southern California researchers found that high-dose omega-3 fish oil supplements successfully reached the brain but produced no improvement in memory or prevention of hippocampus shrinkage in older adults at Alzheimer's risk.
Researchers at the University of Southern California published results in eBioMedicine from a two-year, double-blind, placebo-controlled trial examining whether high-dose omega-3 fish oil supplements protect the brains of older adults at elevated Alzheimer's risk. The study enrolled 365 adults aged 55 to 80 who rarely ate fish; approximately 47% carried the APOE4 gene variant, a key Alzheimer's risk factor. Half received 2,000 mg of docosahexaenoic acid (DHA) daily — a key omega-3 — and half received a placebo. Cerebrospinal fluid measurements confirmed that DHA supplements successfully raised omega-3 levels in participants' brains, with concentrations increasing by an average of 17% after six months. Despite this, participants taking fish oil performed no better on standardised memory and cognitive tests than those taking a placebo. Brain imaging showed that fish oil supplements did not prevent shrinkage of the hippocampus, the brain region most closely associated with Alzheimer's progression. Lead researcher Dr Hussein Naji Yassine concluded that the findings show fish oil supplements do not appear to protect brain health. The team suggested that the benefits of omega-3s observed in epidemiological studies may stem from overall healthy dietary patterns, such as Mediterranean-style eating, rather than from isolated supplements.
