Intake of omega-3 fatty acids, known to boost cognition and mood, could also significantly reduce the chances of developing Alzheimer's disease, said researchers this week.
In a sample of adults aged 65-94, those who ate fish at least once a week had a 60 per cent lower risk of developing the disease compared to those who never or rarely ate fish.
Writing in the Archives of Neurology, the researchers said that a high intake of polyunsaturated fatty acids, found also in nuts and oil-based salad dressings, had reduced the risk of Alzheimer's, although the cause of the debilitating disease which affects an estimated 12 million around the world is not known.
In an editorial in the journal, Dr Robert Friedland of Case Western Reserve University School of Medicine in Cleveland, Ohio, said that fish could be part of a healthy diet to protect against a number of age-related conditions, not just Alzheimer's.
"A high antioxidant/low saturated fat diet pattern with a greater amount of fish, chicken, fruits, and vegetables and less red meat and dairy products is likely to lower the risk of Alzheimer's disease, as well as that for heart disease and stroke," he wrote.
A study published in the British Medical Journal last year also found that elderly people who eat fish or seafood at least once a week to be at lower risk of developing dementia, including Alzheimer's disease. Other trials have looked at the relationship between saturated fat intake and risk for Alzheimer's but results have been inconclusive. The rising rates of Alzheimer's have been associated with the upward trend in obesity.
The researchers from Rush-Presbyterian St. Luke's Medical Center in Chicago, carried out a prospective study from 1993 to 2000, of a random sample of 815 residents in a nursing home. Aged 65 and over, the participants were initially unaffected by Alzheimer disease. The team followed up the sample for an average of 3.9 years, by which time 131 had developed the disease.
Using information from a dietary questionnaire, results showed that total intake of omega-3 polyunsaturated fatty acids was associated with reduced risk of Alzheimer disease, as was intake of docosahexaenoic acid. Eicosapentaenoic acid was not associated with disease outcome. The associations remained unchanged with additional adjustment for intakes of other dietary fats and of vitamin E and for cardiovascular conditions, said the researchers.