The Mediterranean diet is a nutritional model inspired by the traditional dietary patterns of the countries of the Mediterranean basin, particularly Italy, Greece, Portugal and Spain. The diet comprises high consumption of fruit and vegetables, bread and other cereals, olive oil and fish, making them low in saturated fat and high in monounsaturated fat and fibre.
Researchers from the Columbia University Medical Centre looked at the diet and health of 2,200 people over four years, assessed their neurological health and noted their dietary habits, reported the online edition of BBC News.
Their food intake was given a 'Mediterranean Diet score' of between zero and nine. During the course of the study, 262 people were diagnosed with Alzheimer's disease, a common form of dementia.
Dementia is a disorder of the brain that sometimes causes emotional disturbances and personality change.
The researchers found that, for each additional point on the Mediterranean diet scale, the risk of Alzheimer's dropped by almost 10 percent.
Compared to the third of people who scored worst on the Mediterranean diet scores, those in the mid-ranking group had a 15 percent to 21 percent lower risk of developing Alzheimer's disease, and those with the highest score had a 39 percent to 40 percent lower risk.
The association remained significant even after the researchers adjusted their findings for age, gender, ethnicity, education, caloric intake, weight, smoking and other conditions.
The researchers accept their findings relied heavily on people's memories of what they ate, but said a tested dietary assessment technique had been used.
Nicholas Scarmeas, who led the research, said: "Higher adherence to the Mediterranean diet is associated with a reduction in risk for Alzheimer's disease."