Brain Levels of DHA Rise With Fish Oil, Yet Cognition Stays Unchanged

A U.S. research team investigated whether fish‑oil supplementation could deliver DHA to the brain and improve mental performance. The trial recruited 365 participants aged 55‑80, all of whom ate minimal seafood and were predisposed to Alzheimer’s, with approximately 50 % carrying the APOE4 variant.

Subjects were randomly assigned to receive either a high‑dose DHA supplement or a placebo for a period of two years. Periodic lumbar punctures showed that DHA concentrations in the cerebrospinal fluid increased by about 17 % after six months, confirming successful delivery of the fatty acid to the central nervous system.

Despite this biochemical evidence, standard neuropsychological tests and MRI scans revealed no significant enhancement in memory, reasoning, or hippocampal volume compared with the placebo group. The researchers emphasized that a single nutrient boost does not appear sufficient to alter the trajectory of age‑related cognitive decline.