The age-related decline of cognitive functions generally refers to a mild deterioration in memory performance, executive functions, and speed of cognitive processing. The terms "age-related cognitive decline" (ARCD) and "aging-associated cognitive decline" have been proposed recently to indicate an objective decline in cognitive functioning associated to the ageing process but within normal limits given the person's age. Whether ARCD is expression of a normal ageing process or represents a distinct clinical entity or, eventually, is a continuum with dementia is, at present, difficult to establish. The causes of ARCD are unknown, but some studies have suggested that it may be prevented. Avoidance of cardiovascular and other chronic diseases, high educational level, and maintenance of vision and hearing have been identified as protective factors from ARCD. On the contrary, hypertension, effects of altered metabolism of steroid hormones, smoking, low-complexity occupation, higher density of persons/bedroom in home, and low level of physical activity have been identified as risk factors for ARCD. Recent findings suggest a possible role of diet in the ARCD. In fact, in an elderly population of Southern Italy with a typical Mediterranean diet, high monounsaturated fatty acids energy intake appeared to be associated with a high protection against cognitive decline. Dietary antioxidants, specific macronutrients, estrogens, and anti-inflammatory drugs, may act synergistically with other protective factors, opening new therapeutic interventions for cognitive decline.