No surprise here:
“A review of studies that looked at the effect of the Mediterranean diet on long-term cognitive function established that people who adhered to this way of eating had less cognitive decline, had improvements in cognitive function, or were less likely to develop Alzheimer’s disease compared to people who did not stick to this diet. The Mediterranean diet emphasizes fruits, vegetables, whole grains, beans, nuts, fish and olive oil, with lesser amounts of poultry and cheese and limited amounts of red meat and sweets.”
Source: Keeping Alzheimer’s Disease at Bay – Diabetes Self-Management
Advanced Mediterranean Diet 