Overview
- A randomized, double‑blind, placebo‑controlled trial published in June 2026 enrolled 365 adults aged 55–80 at increased Alzheimer’s risk and gave half 2,000 mg of DHA daily for 24 months.
- Cerebrospinal fluid measurements at six months showed an average 17 percent rise in brain DHA among people taking the supplement, confirming the capsules crossed into the brain.
- Despite that target engagement, two‑year cognitive tests and MRI scans found no benefit from DHA and no protection against hippocampal volume loss compared with placebo.
- About 47 percent of participants carried one copy of the APOE4 gene, so the null result most directly applies to older, low‑fish‑intake adults at elevated genetic risk and should not be overgeneralized.
- Lead investigators plan mechanistic studies to learn why DHA uptake did not translate to clinical benefit and they urge emphasis on whole‑diet and lifestyle prevention while exploring ways to improve brain use of omega‑3s.