Elderly people who eat fish or seafood at least once a week are at lower risk of developing dementia, including Alzheimer's disease, finds a study in this week's British Medical Journal.
The study confirms the positive role played by nutrition, in particular fish fatty acids, on mental health.
Using data from a large ageing study, a team of French researchers set out to test whether there was a relation between consumption of fish (rich in polyunsaturated fatty acids) or meat (rich in saturated fatty acids) and risk of dementia.
The study involved 1,674 people aged 68 and over without dementia and living at home in southwestern France. Their frequency of consumption of meat and fish or seafood was recorded as daily, at least once a week (but not every day), from time to time (but not every week), or never. Participants were followed up two, five, and seven years afterwards.
Participants who ate fish or seafood at least once a week had a significantly lower risk of being diagnosed as having dementia in the seven subsequent years. When education was taken into account, the strength of the association was slightly reduced, suggesting that this "protective" effect was partly explained by higher education of regular consumers, said the authors.
They found no significant association between meat consumption and risk of dementia.
As well as providing vascular protection, the fatty acids contained in fish oils could reduce inflammation in the brain and may have a specific role in brain development and regeneration of nerve cells, suggested the authors.
They noted that healthy dietary habits acquired in infancy could be associated with achievement of higher education. But also, highly educated people might also adhere more closely to dietary recommendations on fish consumption.