Scientists say people who eat large quantities of fresh fruits and vegetables, nuts, fish and olive oil have a lower risk of age-related diseases such as dementia.
The research, by the University of Exeter's Medical School, comes after a study last month showed the same diet could help counteract a genetic risk of strokes.
The team, supported by the National Institute for Health Research Collaboration for Leadership in Applied Health Research and Care in the South West Peninsula, analysed research and found a Mediterranean diet was associated with better cognitive function, lower rates of cognitive decline and a reduced risk of Alzheimer's disease. However, results for mild cognitive impairment - the stage before Alzheimer's or dementia - were inconsistent.
Lead researcher Iliana Lourida said: "Our systematic review shows it may help to protect the ageing brain by reducing the risk of dementia."