In a 2006 study, Columbia University Medical Center researcher Nikolaos Scarmeas, MD, and colleagues showed that elderly New Yorkers whose eating habits most resemble the Mediterranean diet have about a 40% lower risk of Alzheimer's disease than do those with poor diets.
A new study of 1,410 older men and women living in France confirms that those who most adhere to the Mediterranean diet have slower age-related cognitive decline than those whose diets least resemble the Mediterranean diet.
And in an update on their earlier study, Scarmeas and colleagues report that among the 1,880 mixed race/ethnicity Americans in their ongoing study, those who get the most physical activity get the least Alzheimer's disease.
These effects add up: The most adherent Mediterranean diet followers who stayed most physically active had a 61% to 67% lower risk of Alzheimer's disease. It's not a matter of eating less and exercising more, Scarmeas tells WebMD -- it's a matter of eating well and staying active.
"It is not how much you eat but how well you eat," he says. "If you take two people at the same weight, the one that exercises or has the healthy diet will have the benefit."
The mental health benefits of the Mediterranean diet and of physical activity were very similar, but independent.
"If two people are eating the same healthy diet, that person who also gets physical activity has much lower risk of Alzheimer's disease compared with the person who is not active," Scarmeas says. "And if both are active, the one with the healthy diet has much lower risk than the person with a less healthy diet."
Mediterranean Diet No Quick Fix for Mental Decline
Unlike the typical American diet, the Mediterranean diet:
• Is very low in red meat and poultry
• Is very high in fruits, nuts, legumes, vegetables, and cereals
• Is high in fish
• Permits low-to-moderate amounts of wine
• Uses olive oil as the main source of fat
Scarmeas notes that both his study and the French study (in which he served as a co-investigator with study leader Catherine Feart, PhD, of INSERM) do not prove that either the Mediterranean diet or exercise will protect a person against Alzheimer's disease or cognitive decline.
"We need a clinical trial to have a higher degree of certainty, but we know these types of behaviors are beneficial in terms of other conditions and diseases," he says. "So it may be good to follow them even with just this preliminary hint they are good for brain health. And just one of these behaviors may not be enough. It may be best to focus on both eating well and staying active."
Elderly people who have a lower risk of Alzheimer's disease probably did not wait until their 70th birthdays to start a healthy lifestyle, notes Mayo Clinic neurologist David S. Knopman, MD.
"To the extent they have an effect on the brain, healthy diet and physical activity probably act over many decades," Knopman tells WebMD.
Is there some special component of the Mediterranean diet that fights Alzheimer's disease? Maybe. But Knopman notes that the Scarmeas study compared those who most closely followed the Mediterranean diet to those who least followed it.
"In the U.S., those who least adhere to the Mediterranean diet would be eating double cheeseburgers and other fast food," he says. "The findings might mean there's something bad in this diet, rather than something good in the Mediterranean diet."
Knopman says the main message of the Scarmeas and Feart studies is that diet is a very important part of a healthy lifestyle. Studies link the Mediterranean diet not only to slower mental decline but to lower risk of heart disease, cancer and early death.
"This diet can't be so fantastic that it has biochemical effects on all these things -- that stretches credibility," Knopman says. "It seems more likely these studies are picking up on some healthy lifestyle behaviors and other factors that began in childhood."
The Scarmeas and Feart studies, and an editorial by Knopman, appear in the Aug. 12 issue of the Journal of the American Medical Association.
By Daniel J. DeNoon
Reviewed by Louise Chang, MD
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