Studies published in the August 12, 2009 issue of the Journal of the American Medical Association (JAMA) reveal a decreased risk of Alzheimer's disease (AD) and cognitive decline among individuals who report greater adherence to a Mediterranean type diet. The diet includes high amounts of fruits, vegetables, legumes, cereal, fish, and monounsaturated fats, lower amounts of saturated fats, red meat and poultry, and moderate alcohol consumption.
In one article, Nikolaos Scarmeas, MD, of Columbia University Medical Center and his associates evaluated data from 1,880 elderly men and women who did not have dementia upon recruitment into the Washington Heights-Inwood Columbia Aging Project. The subjects received neurological and neuropsychological testing every 1.5 years for an average 5.4 year follow-up period, during which 282 participants were diagnosed with Alzheimer's disease.
Greater physical activity alone was associated with a lower risk of Alzheimer's disease, with a 25 percent average reduction in risk associated with some activity compared to no activity. Those who were categorized as participating in "much" physical activity experienced a 33 percent average lower risk.
When adherence to a Mediterranean diet was considered, those in the middle third of participants had an average 2 percent reduction in the risk of developing Alzheimer's disease, while those in the top third had experienced a 40 percent reduction compared to those in the lowest third.
Having both high levels of physical activity and adherence to the diet were also associated with a protective benefit. “Compared with individuals with low physical activity plus low adherence to a diet, high physical activity plus high diet adherence was associated with a 35 percent to 44 percent relative risk reduction," the authors write. “In summary, our results support the potentially independent and important role of both physical activity and dietary habits in relation to AD risk. These findings should be further evaluated in other populations.”
In a second study published in the journal, greater adherence to a Mediterranean diet was associated with a reduction in cognitive decline.
Catherine Féart, PhD, of the Université Victor Ségalen in Bordeaux, France, and colleagues evaluated data from 1,410 participants aged 65 years and older in the Three-City cohort, a study of vascular risk factors and dementia. Participants were assessed for cognitive performance during 2001-2002 and were re-examined at least once over the following 5 years. Dietary questionnaires were scored from 0 to 9 for Mediterranean diet adherence.
Although greater adherence to the diet was associated with fewer errors over time on one neuropsychological test, indicating a reduction in cognitive decline, the risk of developing dementia was not associated with diet adherence.
“A variety of approaches to mitigating cerebrovascular disease in midlife exist, including diet, exercise, treatment of hypertension, treatment of diabetes, avoidance of obesity, and avoidance of smoking," writes David S. Knopman, MD, of the Mayo Clinic in an accompanying editorial. "The findings of Scarmeas et al and Féart et al fit into a larger and potentially optimistic view of prevention of late-life cognitive impairment through application, at least by midlife, of as many healthy behaviors as possible, including diet. Based on these 2 studies, diet may play a supporting role, but following a healthy diet does not occur in isolation.”
“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.”