People who eat oily fish or take fish oil supplements score 13 per cent higher in IQ tests and are less likely to show early signs of Alzheimer's disease, according to a new study in Scotland.
The study, carried out on more than 300 people, lends support to the benefits of fish oil - already taken to protect the heart - for mental health and particularly for its protective effects against Alzheimer's.
Dementia already affects millions around the world and the threat is increasing with the growing numbers of elderly. Alzheimer's disease, the leading cause of dementia in the elderly, afflicts an estimated 4.5 million people in the US alone.
A team from the University of Aberdeen and the University of Edinburgh gathered data from people who had taken part in a national IQ survey in 1947, when they were aged 11, and tested them again in 2000-01 when they were aged 64. The researchers used a questionnaire to find out about omega-3 levels from the subjects' diet and supplement use, and tested their plasma levels of omega-3.
Writing in this month's American Journal of Clinical Nutrition (vol 80, no 6, pp1650-1657), the researchers report that cognitive function in the 64-year-olds was higher if they were supplement users than if they did not take supplements.
After adjustment for childhood IQ, tests for mental speed found food supplement users to have a higher score.
Lawrence Whalley, a professor of mental health at Aberdeen University and head of the research team, told The Times that there was evidence that fish oils slow the ageing of the brain by reducing inflammation.
"The big difference we found was not in memory but in mental speed," he told the paper. "The brains of fish oil users seemed to be faster. There was a strong relationship between mental test scores and the omega-3 content in the blood."
"The results suggest to me that they have younger brains than the non-users. The ageing of their brain is being slowed down by a year or two."