Overview
- The randomized, double‑blind trial led by USC enrolled 365 adults aged 55–80 with low fish intake and at least one dementia risk factor and tested 2,000 mg of DHA daily over 24 months.
- The study, published June 18 in eBioMedicine, confirmed target engagement with cerebrospinal fluid DHA rising about 17% while blood omega‑3 levels also climbed in the treatment group.
- Despite brain uptake, participants who received DHA showed no improvement on standardized cognitive tests and scans showed no protection against hippocampal atrophy compared with placebo.
- Nearly half the participants carried at least one APOE4 gene copy and all started with very low omega‑3 levels, so investigators say the null result applies to this at‑risk, low‑fish‑intake group rather than every population.
- Authors and commentators urged shifting prevention efforts toward whole‑diet and lifestyle measures, said researchers will pursue mechanistic work and drug development to help the brain use omega‑3s, and noted the result has implications for a market that spends over $1 billion a year on fish oil supplements.