The study's lead researcher, Dr. Nikolaos Scarmeas, first reported a possible link between the Mediterranean diet and Alzheimer's disease in June in the journal Annals of Neurology. Scarmeas' first study, involving over 2,200 New York residents, found lower risk of Alzheimer's among participants who followed the diet, which includes high levels of fruits, vegetables, nuts, grains, beans, olive oil and fatty fish. Red meat is rarely eaten, and eggs, dairy and poultry are consumed in moderation.
To confirm the results of their June study, Scarmeas and colleagues repeated the study on about 2,000 people who either suffered from Alzheimer's or were at high risk of developing the disease. Roughly one in 10 participants were already diagnosed with Alzheimer's, and the average age of the patients was 76.
The researchers reviewed the diets of the study participants over the course of a year, and found that those who most closely followed the Mediterranean diet experienced a 40 to 65 percent lower risk of Alzheimer's disease than those who did not closely follow the diet.
Scarmeas -- whose latest study was published in the online issue of the journal Archives of Neurology -- said that although there is some evidence of a genetic influence on Alzheimer's, doctors do not know the cause of the vast majority of cases. "But there is plenty of room for environmental influences, like diet, to play a role," Scarmeas said.
A separate study published in the October issue of Archives of Neurology found that in patients who were experiencing mild mental decline associated with the onset of Alzheimer's, supplementing the diet with omega-3 fatty acid pills slowed the progression of the disease.
Researchers from Sweden's Karolinska Institute and Uppsala University Hospital examined 204 patients with mild to moderate Alzheimer's, and found that among patients with very mild symptoms, mental decline slowed after omega-3 supplementation. Researcher Dr. Tommy Cederholm called the results "clinically relevant, but not dramatic," and called for further research.
Nutritionist Mike Adams, author of "The Seven Laws of Nutrition," said both studies demonstrate the strong correlation between diet and brain function.
"Deterioration of cognitive function is not, as most people believe, something we are automatically doomed to experience as we age," Adams said. "Most of the cognitive decline we observe in the population today is due to dietary causes, not natural aging. A well-nourished brain that is kept active and engaged can function at peak levels well beyond age 100."