Two-Year Trial: Fish Oil Supplements Deliver Omega-3 to the Brain But Fail to Prevent Cognitive Decline
A large clinical trial found that high-dose fish oil capsules raised omega-3 levels in the brains of older adults at Alzheimer's risk but produced no improvement in memory or prevention of hippocampal shrinkage.
A two-year, randomised, double-blind, placebo-controlled clinical trial led by the University of Southern California and published in eBioMedicine found that high-dose DHA omega-3 fish oil supplements did not protect cognition or brain structure in older adults at elevated risk of Alzheimer's disease. The study enrolled 365 adults aged 55 to 80 who rarely ate fish; about 47 per cent carried the APOE4 gene, the strongest genetic risk factor for late-onset Alzheimer's. Participants taking the supplements showed a 17 per cent rise in omega-3 concentrations in their cerebrospinal fluid after six months, confirming the fatty acids were reaching the brain. Despite this, cognitive testing and MRI brain imaging showed no significant advantage over the placebo group: memory scores were equivalent, and the supplements did not prevent shrinkage of the hippocampus — the brain region most associated with memory and most vulnerable to Alzheimer's. Lead investigator Dr Hussein Naji Yassine concluded that getting omega-3s from a balanced whole diet may offer benefits that isolated supplementation cannot replicate. The findings challenge a widely held assumption among the millions of people who take fish oil for brain health.
