A Mediterranean diet, comprising fruits, vegetables, olive oil and fish, may help older adults to retain more brain volume, researchers have found.

The Mediterranean diet also includes beans and cereal grains such as wheat and rice, moderate amounts of fish, dairy and wine and limited red meat and poultry.

"As we age, the brain shrinks and we lose brain cells which can affect learning and memory. This study adds to the body of evidence that suggests the Mediterranean diet has a positive impact on brain health," said Michelle Luciano from the University of Edinburgh in Scotland.

For the study, researchers gathered information on the eating habits of 967 Scottish people aged around 70 who did not have dementia.

The findings showed that people who did not follow as closely to the Mediterranean diet were more likely to have a higher loss of total brain volume over three years than those who followed the diet more closely.
 

The difference in diet explained 0.5 per cent of the variation in total brain volume, an effect that was half the size of that due to normal ageing.

The results were the same when adjusted for other factors that could affect brain volume such as age, education and having diabetes or high blood pressure, the researchers said.

In addition, consuming fish and meat were not related to brain changes, they said. This is contrary to earlier studies.

"It's possible that other components of the Mediterranean diet are responsible for this relationship or that it's due to all of the components in combination," Luciano said.

No relationship was found between grey matter volume or cortical thickness -- which is the outer layer of the brain -- and the Mediterranean diet, the researchers noted.

The study is published online in the journal Neurology.