Scientists have known the diet – which is typical in Spain – can help prevent dementia, but they did not know how it protected the brain.
But a new study has shown how it keeps brain cells active for longer, helping to slow down the inevitable shrinkage.
“As we age, the brain shrinks and we lose brain cells which can affect learning and memory,” said the author of the study Dr Michelle Luciano, from the University of Edinburgh.
“This study adds to the body of evidence that suggests the Mediterranean diet has a positive impact on brain health… and may be able to provide long-term protection to the brain.”
Scientists gathered dietary information for 401 70 year olds and then scanned their brains at the age of 73 and 76, measuring brain volume and the thickness of the cerebral cortex.
They found that those who closely followed a Mediterranean diet – oily fish, vegetables, nuts and fruit – retained more volume over the period.
Dr Clare Walton, Research Manager at Alzheimer’s Society, said: “There is an increasing amount of evidence to indicate that eating a healthy diet that’s rich in oily fish, fresh veg and nuts is good for your brain and can help to maintain your memory as you get older.
“Our brains shrink by 1-2 per cent per year in old age and this study suggests that a Mediterranean-style diet could also potentially help to slow down this shrinking process.”