With the demographic aging of populations worldwide, diseases associated with aging are becoming more prevalent and costly to individuals, families, and healthcare systems. Among aging-related impairments, a decline in cognitive function is of particular concern, as it erodes memory and processing abilities and eventually leads to the need for institutionalized care. Accumulating evidence suggests that nutritional status is a key factor in the loss of cognitive abilities with aging. This is of tremendous importance, as dietary intake is a modifiable risk factor that can be improved to help reduce the burden of cognitive impairment. With respect to nutrients, there is evidence to support the critical role of several B vitamins in particular, but also of vitamin D, antioxidant vitamins (including vitamin E), and omega-3 fatty acids, which are preferentially taken up by brain tissue. On the other hand, high intakes of nutrients that contribute to hypertension, atherosclerosis, and poor glycemic control may have negative effects on cognition through these conditions. Collectively, the evidence suggests that considerable slowing and reduction of cognitive decline may be achieved by following a healthy dietary pattern, which limits intake of added sugars, while maximizing intakes of fish, fruits, vegetables, nuts, and seeds.