“Our findings from this prospective cohort suggest that adherence to a Mediterranean diet is not only a heart healthy diet plan but also one that fosters a healthier functioning brain,” Christine C. Tangney, of the Department of Clinical Nutrition, Rush University Medical Center, Chicago, Illinois, told Medscape Medical News.
Their results were published online December 22, 2010, in the American Journal of Clinical Nutrition.
The Chicago Health and Aging Project
The findings are based on data from 3790 participants with an average age of 75.4 years enrolled in the Chicago Health and Aging Project, an ongoing study of cognitive health in adults 65 years and older. They underwent standard tests of cognitive function on 2 or more occasions at 3-year intervals.
The researchers used a modified version of the Harvard food-frequency questionnaire to assess level of adherence to 2 dietary patterns. One was the traditional MedDiet pattern, which is rich in olive oil, fish, nuts, fruits and vegetables, and moderate amounts of wine and is low in dairy foods and red meat. The other was the Healthy Eating Index 2005 (HEI-2005), which is based on recommendations from the 2005 Dietary Guidelines for Americans.
The maximum score for the MedDiet, which would mean complete adherence, is 55, and participants’ mean score was 28.2. The maximum score for the HEI-2005 is 100, and participants’ mean score was 61.2.
Participants most likely to adhere to the MedDiet were white, nonsmokers, and multivitamin users, with higher educational levels and lower body mass index. Those with higher MedDiet scores had lower prevalence of stroke, hypertension, and depression and higher baseline global cognitive scores.
Brain Age ‘Years Younger’ With MedDiet
According to the investigators, a higher MedDiet score indicating closer adherence to this eating pattern was associated with slower rates of cognitive decline over time, after adjusting for age, sex, race, education, participation in cognitive activities, and energy.
“If we were comparing 2 persons with MedDiet scores or MedDiet wine scores that were 10 points apart, the person with the higher scores would appear to perform as if she or he were 3 years younger cognitively,” the study authors note.
In contrast, higher scores on the HEI-2005, which gives less weight to fish, legumes, and moderate alcohol intake, were not associated with baseline cognitive scores or rate of cognitive decline.
Reached for comment, Nikolaos Scarmeas, MD, MSc, associate professor of neurology, Columbia University Medical Center in New York City, said the finding that associations between a MedDiet and lower risk for cognitive decline were “very strong,” yet there was no association between the HEI-2005 and cognitive decline, “underscores the potential benefits of a Mediterranean-type diet compared to other nonspecific healthy dietary patterns.”
The fact that the study authors used a MedDiet scoring system in relation to intakes seen in Greek populations is a strength of the study, Dr. Scarmeas added. “Other investigative groups assessed each component based on cutoffs driven by their population distribution, not the Greek population,” Dr. Tangney explained.
“It is very important and at the same time reassuring to replicate previous findings in different cohorts and populations,” as this study does, Dr. Scarmeas said.
The Chicago study is consistent with earlier reports from a triethnic Northern Manhattan cohort study, which Dr. Scarmeas was involved in, that showed higher MedDiet scores were associated with reduced risk for incident mild cognitive impairment and incident Alzheimer’s disease.
There is a biological basis for the apparent neuroprotective effects of a MedDiet, Dr. Tangney and colleagues note in their report.
“A myriad of studies — clinical trials and cohort — point to the value of such a dietary pattern in reducing markers of oxidative stress and in altering expression of anti- and proinflammatory markers thought to play a role in the pathogenesis of vascular diseases as well as Alzheimer’s disease,” they point out. It’s also possible that years of eating a MedDiet may prevent or mitigate cerebrovascular disease or may influence β-amyloid or tau metabolism.
Dr. Tangney feels it is “important to educate, support, and motivate our patients to make the kinds of dietary changes reflective of such a Mediterranean-type diet plan, which may down the road protect their brain from rapidly deteriorating cognitive changes.
“This means getting an experienced dietitian to assess their diet and who will design this newer diet plan,” she added. “Then all members of the healthcare team can support the patient to stay committed to these changes.”