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A number of studies have suggested that omega-3 fatty acids may help keep nerve cells in the brain healthy into old age, but there is limited evidence for the role of these fatty acids in preventing dementia or decreased mental abilities -- known as "cognitive decline."
To examine this issue more closely, Emma Sydenham and colleagues at the London School of Hygiene & Tropical Medicine in England reviewed evidence from three studies that compared the effects of omega-3 fatty acids taken in capsules or margarine to the effects of placebo capsules with sunflower oil or olive oil, or regular margarine (the "control" group).
The studies included a total of more than 3,500 people over the age of 60 and lasted between six and 40 months. None of the participants showed any signs of problems with their thinking skills or dementia at the start of the studies.
People who consumed omega-3 fatty acid-containing capsules or margarine did no better on standard tests of mental abilities or on tests of memory and verbal skills, according to the findings published in The Cochrane Library.
"From these studies, there doesn't appear to be any benefit for cognitive health for older people of taking omega-3 supplements," report co-author Alan Dangour, a nutritionist at the London School of Hygiene & Tropical Medicine, said in a Cochrane news release.
"However, these were relatively short-term studies, so we saw very little deterioration in cognitive function in either the intervention groups or the control groups. It may take much longer to see any effect of these supplements," he added.
The researchers said further studies are needed to assess the long-term effects of omega-3 fatty acids on mental decline, particularly in people with low dietary intake of omega-3 fatty acids.
Oily fish such as salmon and mackerel are a source of omega-3 fatty acids and other health benefits. "Fish is an important part of a healthy diet and we would still support the recommendation to eat two portions a week, including one portion of oily fish," said Dangour.
-- Robert Preidt
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