Diet and dementia: The epidemiological approach

As the population is aging, the cases of dementia and its most common cause, Alzheimer's disease (AD), are increasing, along with the associated public health burden. Preventive and therapeutic measures for dementia and AD are limited, justifying the increased scientific interest in the role of nutrition as a risk factor for dementia and AD. The goal of this review is to summarize the most important epidemiological evidence concerning the associations between dietary factors and dementia and to present the dominant biological theories that have been developed to explain the reported associations. Although the results of different studies are often contradictory, certain associations are frequently encountered. As far as food groups and dietary patterns are concerned, a higher intake of fruits, vegetables and fish, and moderate consumption of wine may be related to a lower incidence of dementia and AD, and adherence to the Mediterranean diet has been suggested to be protective against AD. As far as nutrients are concerned, a higher intake of antioxidants such as vitamin E, a higher intake of B-complex vitamins, especially folate, a higher intake of monounsaturated fatty acids and n-3 polyunsaturated fatty acids and moderate intake of alcohol may lower the risk of dementia and AD. In addition, a higher intake of total, trans-unsaturated and saturated fat has been associated with increased risk of dementia and AD. Despite the associations that emerged in observational studies, interventional primary and secondary prevention trials conducted to date (most notably with vitamin E and homocysteine-lowering B-complex vitamin therapy) have not confirmed the role of any nutritional factors. Conflicting data preclude the issue of dietary recommendations for the prevention of dementia and AD at this point. Additional prospective studies with sufficient follow-up time and control for confounding factors, as well as prevention trials and meta-analyses are needed to document the associations already observed or yet unobserved between dietary factors and dementia with the aim of contributing to the prevention of dementia and AD.