The risk of developing Alzheimer's and dementia could be reduced by a diet rich in fish, fruit and vegetables, new research has suggested.

A study examined the eating habits of more than 8,000 men and women who were over the age of 65 and did not have any mental health issues when the study began.

In the four-year investigation, 281 of the participants developed various types of dementia, including Alzheimer's.

Researchers found that people who regularly ingested omega-3 rich oils were at a 60 per cent reduced risk of such conditions.

Those who ate fish at least once a week had a 35 per cent reduction in their risk of Alzheimer's and a 40 per cent lower chance of dementia.

Author of the study Dr Pascale Barberger-Gateau from the French National Institute for Health and Medical Research commented: "These results could have considerable implications in terms of public health."

The Alzheimer's Society states that there are over 100 different types of dementia.