A review of three high quality trials comparing the putative benefits of omega-3 fatty acids for preventing age-related cognitive decline, has concluded that there is no evidence that taking fish oil supplements helps fight cognitive decline. The trials involved a total of 3,536 healthy older adults (60+). In two studies, participants were randomly assigned to receive gel capsules containing omega-3 PUFA or olive or sunflower oil for six or 24 months. In the third study, participants were randomly assigned to receive tubs of margarine spread for 40 months (regular margarine versus margarine fortified with omega-3 PUFA).
The researchers found no benefit from taking the omega-3 capsules or margarine spread compared to placebo capsules or margarines (sunflower oil, olive oil or regular margarine). Participants given omega-3 did not score better on the MMSE or on other tests of cognitive function such as verbal learning, digit span and verbal fluency.
The researchers nevertheless stress that longer term studies are needed, given that there was very little deterioration in cognitive function in any of the groups.
 . Omega 3 fatty acid for the prevention of cognitive decline and dementia. In: Cochrane Database of Systematic Reviews. Cochrane Database of Systematic Reviews. Chichester, UK: John Wiley & Sons, Ltd; 2012. Available from: http://summaries.cochrane.org/CD005379/fish-oils-for-the-prevention-of-dementia-in-older-people