Life span refers to the age at death of the longest lived individual of a species and exceeds 120 years in humans. The potential for diet-related factors to influence life span is usually studied in experimental systems. Maximal life span of numerous species is increased by calorie restriction, but the effect in humans is not yet known.

Life expectancy is the number of years an individual is expected to live. Longevity is generally defined in terms of life expectancy. The influence of diet on human life expectancy has been studied in long-term perspective cohort studies lasting up to several decades. These types of studies generally show that consumption of fruits, vegetables, whole grains, and/or nuts decreases mortality from many age- and diet-related diseases.