A diet rich in olive oil, nuts, fish, poultry and certain fruits and vegetables may have an effect at reducing the risk of Alzheimer's disease, researchers report.
People who ate nutrients specifically selected for brain health had a 40 percent lower risk of developing Alzheimer's disease compared with others, Dr Yian Gu of Columbia University in New York and colleagues found.
"Diet is probably the easiest way to modify disease risk," says Gu, whose study appears in Archives of Neurology.
She says because there are no cures for Alzheimer's, prevention is key; especially as the population ages.
"If we follow this diet, that means the risk of getting the disease will be lowered for the population," says Gu.
While other studies have looked at individual nutrients, Gu's team studied groups of foods high in nutrients that have been shown to be associated with Alzheimer's disease risk.
Some, such as saturated fatty acids in red meat and butter, need to be avoided. Others, such as omega-3 fatty acids, omega-6 fatty acids, vitamin E, vitamin B12 and folate, benefit the brain.
The good oils
To study this, the team collected information on the diets of 2148 healthy people over 65 years for an average of four years. They were checked for Alzheimer's disease every 18 months. Of these, 253 developed Alzheimer's.
Those least likely to develop the disease - 50 out of 682 (7%) - ate more olive oil-based salad dressing, nuts, fish, tomatoes, poultry, broccoli, fruits, and green leafy vegetables.
This compared to 117 out of 749 (16%) of those who were more likely to eat high-fat dairy, red meat and butter in their diet.
"People who adhered mostly to this dietary pattern compared to others have about a 40% reduction in the risk of developing Alzheimer's disease," says Gu.
She says the diet likely works in two ways. Because it is rich in heart-healthy foods, it may be protecting the brain from strokes that could make it more vulnerable to Alzheimer's disease.
But it also may be that the nutrients - such as omega-3 fatty acids, antioxidants and folate - directly protect the brain.
Current treatments help with some symptoms, but cannot reverse the course of Alzheimer's, a mind-robbing form of dementia that affects more than 26 million people globally.