The pathophysiology of Alzheimer’s disease is complex. Both genetic and environmental factors are considered to be involved. Among the latter, nutrition may play a major role. Longitudinal cohort studies have found that people who closely follow the Mediterranean diet, the DASH diet, and the MIND diet undergo less cognitive decline over time and have lower rates of dementia and Alzheimer’s disease. However, interventional studies are needed to establish a causal relationship. In this connection, clinical studies based on the Mediterranean diet have reported positive results for cognitive performance. The beneficial results obtained by certain diets have not been achieved by supplementation with individual nutrients, suggesting that added benefit may be derived through the association of foodstuffs, for instance as occurs in the diet, as opposed to when they are administered separately. Research into nutrients beneficial to brain function has been carried out, and medical foods with good safety and tolerability profiles have been designed and have yielded promising results in the treatment of mild Alzheimer’s disease.