Two new studies are providing more evidence that what we eat can affect the health of our brains.
The studies, published in JAMA, the Journal of the American Medical Association, found that a Mediterranean-style diet can have a significant effect on dementia.
The Mediterranean diet calls for lots of vegetables, beans, fish and olive oil, a moderate amount of alcohol, and is low in meat, poultry and dairy.
One of the JAMA studies found that those who followed the diet -- and who were also physically active -- had a lower risk of Alzheimer's disease.
The second study did not note a decreased risk of dementia in those following the diet, but it did find that those patients who stuck most closely to the diet had slower cognitive decline.
The Mediterranean-style diet has already been linked to lower risk for death and chronic diseases. It's also been linked to reduced risk for dementia in previous studies.
But this new research was designed to explore whether it was the diet that was linked to lower dementia risk or whether it was a lifestyle that included a healthy diet and exercise that lowered the risk.
A team led by Dr. Nikos Scarmeas, of the Department of Neurology, in the Sergievsky Center and in the Taub Institute for Research on Alzheimer's Disease and the Aging Brain at Columbia University Medical Center, looked at 1,880 people of diverse ethnicity living in Manhattan.
Their average age was 77 and none had dementia at the start of the study.
The participants were interviewed about their level of physical activity and dietary habits. They were then followed for an average of more than five years, during which time 282 developed Alzheimer's.
The study found:
- Those seniors who were very physically active had a 33 per cent risk reduction of Alzheimer's disease.
- Those who adhered more strongly to a Mediterranean-type diet had a 40 per cent risk reduction
- Those who reported they were both exercising a lot and following a diet closer to the Mediterranean-style had a 60 per cent risk reduction of developing Alzheimer's.
"So it seemed that the more that they were doing in terms of both diet and exercise, the lower was their risk for the disease," Dr. Scarmeas said in a statement.
"This study is important because it shows that people may be able to alter their risk of developing Alzheimer's by modifying their lifestyles through diet and exercise," he added.
It's thought that the Mediterranean diet might have protective effects against dementia because it combines several nutrients that might protect against cognitive decline, "such as fish, monounsaturated fatty acids, vitamins B12 and folate, antioxidants (vitamin E, carotenoids, flavonoids), and moderate amounts of alcohol," the authors write.
In a second study, Catherine F�art, of the Universit� Victor S�galen Bordeaux 2, in Bordeaux, France, looked at whether adherence to a Mediterranean diet was associated with change in cognitive performance and with lower risk of all-cause dementia.
The study looked at 1,410 seniors from Bordeaux and found that the more individuals stuck to the diet, the fewer the errors they made on cognitive tests. The researchers did not find Mediterranean diet adherence was linked to the incidence of dementia, but they noted that the statistical strength of the data to detect a difference was limited.
"The Mediterranean diet pattern probably does not fully explain the better health of persons who adhere to it, but it may contribute directly," the authors conclude. "A Mediterranean diet also may indirectly constitute an indicator of a complex set of favorable social and lifestyle factors that contribute to better health."
In an accompanying editorial to the two studies, Dr. David S. Knopman, of the Mayo Clinic in Rochester, Minn., say the two studies fit into a larger view that the risk of dementia might be lowered through as many healthy behaviors as possible, including diet. But he cautioned against reading too much into their findings
He says the Mediterranean-style diet's link to lower risks for dementia, heart disease and cancer "probably reflect a lifetime of exposure both to the diet and to other healthy behaviors."
"The scientific value of these studies cannot be disputed, but whether and how they can or should be translated into recommendations for the public is the question. For now, it is reasonable to nibble on these findings and savor them, but not to swallow them whole."
