Chalk up another endorsement for the so-called Mediterranean diet: The eating regimen, which is rich in fruits, vegetables, fish and olive oil, may help the brain stay sharp into old age, a new study suggests.
Following the healthful diet reduced the risk of getting mild cognitive impairment-marked by forgetfulness and difficulty concentrating And it also cut the risk of developing Alzheimer's disease if cognitive impairment was already present, said study lead author Nikolaos Scarmeas, MD, an assistant professor of neurology at Columbia University Medical Center in New York City.
The study was published in the Archives of Neurology.
Previous research has found that people who follow the Mediterranean diet are at less risk of developing a variety of diseases, including heart disease, cancer and Parkinson's disease.
The Columbia researchers evaluated nearly 1,400 people without cognitive impairment and 482 people with mild cognitive impairment, and then followed them for an average of 45 years. The participants-average age 77—also completed a food frequency questionnaire, detailing what they had eaten during the past year.
The researchers divided the participants into three groups—those who adhered regularly to the Mediterranean diet, those who adhered moderately to it, and those who adhered somewhat or not at all. Then they evaluated the participants' cognitive functioning.
The researchers found that the diet helped prevent both mild cognitive impairment and also the risk of further decline, even if people weren't entirely strict in their adherence to the diet.
"As compared to the group that ate very little or not at all of the Mediterranean diet, those who ate it to a moderate degree had 17% less risk of developing mild cognitive impairment." Dr. Scarmeas said. "Those who adhered a lot had a 28% less risk of developing mild cognitive impairment."
The diet also helped those who already had mild impairment. "Compared to those who adhered not at all or very little, those who ate the Mediterranean diet to a moderate degree had a 45% reduction in risk of going from mild cognitive impairment to Alzheimer's disease. Those who adhered a lot had a 48% reduction in risk of going from mild cognitive impairment to Alzheimer's," he said.
Dr. Scarmeas said previous research he conducted found that a greater adherence to the Mediterranean diet was associated with a lower risk of Alzheimer's disease.
It's not known exactly how the diet may help keep the brain healthy, Dr. Scarmeas said. One possibility is that it might reduce inflammation, which plays a role in brain disease. Or it might work by improving cardiovascular risk factors, such as high cholesterol, he said.
"You see what is called a dose response. The more stringently you follow the Mediterranean diet, the better the outcome," noted Gary Kennedy, MD, director of geriatric psychiatry at Montefiore Medical Center in New York City.
Alice Lichtenstein, DSC, Gershoff Professor of Nutrition Science and Policy at Tufts University in Boston, said, "It's encouraging to see the results—those reporting the healthier dietary pattern seem to do better." What remains to be seen, she added, is whether it was the specific diet that helped people avoid cognitive decline or if those people who ate properly had other healthy habits that decreased their risk.
All three experts agreed: Until more evidence is in that the Mediterranean diet keeps brains sharp, there are plenty of other reasons to follow it, including heart health.