The human life span is increasing and there is a need to maintain functional wellbeing in old age. Cognitive function is a major determinant of quality of life in older age. Cognitive impairment can be influenced by a number of factors and the effect of nutrition on cognitive function has become a topic of increasing scientific and public interest. The data available are not sufficient for definitive conclusions to be drawn regarding the relationship between diet and dementia, which is the most common form of cognitive impairment in the elderly; however, there is evidence that dietary lipids, oxidative stress and related antioxidant vitamins, and homocysteine-related vitamins can affect the risk of dementia. This review provides a brief overview of this topic.