Globally, about 42 million people now have dementia, with Alzheimers disease as the most common type of dementia. Rates of Alzheimers disease are rising worldwide. The most important risk factors seem to be linked to diet, especially the consumption of meat, sweets, and high-fat dairy products that characterize a Western Diet. For example, when Japan made the nutrition transition from the traditional Japanese diet to the Western diet, Alzheimers disease rates rose from 1% in 1985 to 7% in 2008, with rates lagging the nutrition transition by 20-25 years. The evidence of these risk factors, which come from ecological and observational studies, also shows that fruits, vegetables, grains, low-fat dairy products, legumes, and fish are associated with reduced risk. Using Multicountry Ecological and Observational Studies to Determine Dietary Risk Factors for Alzheimers Disease, a review article from the Journal of the American College of Nutrition presents the data.