Diet and the risk for Alzheimer's disease

For centuries, the role of diet in the causation and prevention of disease has engaged scientific and lay interest. The hope, presumably, is that by identifying (and consuming) significant amounts of a single nutrient or set of nutrients, we can prevent disease and promote longevity. Clinical studies of vitamins and other micro-nutrients are published regularly in support of this notion, and the results are highlighted routinely in newspapers, magazines, and popular media. In this issue of Annals of Neurology, Scarmeas and colleagues1 report an observational study of the Mediterranean diet and risk for Alzheimer’s disease (AD) in a multiethnic population sample in northern Manhattan. The Mediterranean diet is characterized by high intake of foods and nutrients that have been reported to be beneficial in AD, including fruits, vegetables, fish, unsaturated fatty acids, and modest amounts of wine. After adjustment for numerous potential confounders, individual food groups were not significantly associated with risk for AD, but the composite Mediterranean dietary pattern (highest tertile) was associated with a 40% reduction in AD risk when compared with the lowest tertile (hazard ratio, 0.60; confidence interval, 0.42–0.87). The results of Scarmeas and colleagues’ study1 are consistent with other studies that show benefit of the composite Mediterranean diet on cognitive performance,2 as well as mortality cardiovascular disease, and cancer outcomes.3–5 The work of Scarmeas and colleagues1 extends the approach in the study of diet and AD risk from individual foods and nutrients to a composite dietary pattern. As they emphasize, “defining diet by dietary patterns has the ability to capture its multi-dimensionality…because patterns can integrate complex or subtle interactive effects….” It makes scientific sense to consider dietary patterns because this conception more closely approximates the way people consume our nutrients. Defining diet by dietary patterns, of course, also has limitations. In particular, we can only speculate on the key mechanisms and interactive effects underlying any observed benefits of a dietary pattern. Some components of the diet may actually be antagonistic or even harmful, and these effects would be difficult to detect.