Do fish oil pills keep my memory sharp?

DHA and EPA, the fatty acids in fish oil, are incorporated into the walls of brain cells. In mouse studies, DHA improves memory and reduces harmful protein accumulation in the brain¹. At the cellular level, DHA also stimulates the production of a lipid that supports signal transmission in brain cells². The biological story sounds plausible, but in humans that benefit has not yet been demonstrated.

When fish oil is tested as a standalone supplement in humans, the outcomes are disappointing. A broad systematic review of treatments for dementia classified omega-3 as ineffective for cognitive complaints³. A second review added that omega-3 supplements appear less protective than a Mediterranean diet as a whole⁴. The dietary context surrounding fish therefore seems to matter, not the isolated supplement.

One large human study gives reason for additional caution. In 197 older adults with mild memory complaints, DHA-rich fish oil was combined with cocoa flavanols for twelve months. On the primary outcome measure, no improvement was observed. For planning and organising, and for alertness, the fish oil group even scored slightly worse than the control group. The volume of the cerebral cortex also decreased slightly⁵. The effects were small, but they are a warning signal.

There is also a more positive study. A 24-month study in sixty healthy adults aged 65 and over found that a combination supplement of fish oil, carotenoids and vitamin E significantly improved working memory compared with placebo⁶. However, the effects were modest, several researchers had financial ties to supplement manufacturers, and the supplement contained more than fish oil alone. Which ingredient made the difference remains unclear.