INTRODUCTION: The prevention of Alzheimer's disease (AD) has become a real challenge due to its rising prevalence and the lack of an effective cure. Diet and nutrients have gained significant interest as potentially modifiable protective factors. PURPOSE: The aim of this review is to provide an updated summary of evidence related to the effect of diet and nutritional factors on the risk of AD and cognitive aging, and discuss the potential mechanisms and confounding factors involved. METHODS: A search was conducted in Medline and Web of Knowledge for epidemiological and clinical studies in the international literature from January 2000 to February 2013 using combinations of the following keywords: "Alzheimer's disease", "mild cognitive impairment", "cognitive function", "dietary factors", "omega-3", "antioxidants", "B vitamins", "dietary patterns", and "Mediterranean diet". RESULTS AND CONCLUSION: Data from observational studies point to a protective role for certain nutrients, such as omega-3 fatty acids, antioxidants or B vitamins, and dietary patterns (Mediterranean diet). However, data from randomized controlled trials do not show a consistent effect. Whether confounding factors such as age, disease stage, other dietary components, cooking processes, and other methodological issues explain the divergent results remains to be established. Moreover, if certain nutrients protect against dementia, it is as yet unknown whether they may have a general effect on brain vascular health or directly interfere with the etiopathogenesis of AD.