Dietary alteration in the rates of cancer and aging.

Both variation of diet and comparative analysis are used to evaluate the effects of nutrition on mortality and cancer. The effects of caloric restriction (CR) are compared in multiple strains raised under similar conditions for a diet developed to assist breeding, and for a standard diet. A standard analysis, using "aging rates," is of limited use for understanding the effects of CR in delaying mortality in certain strains. However, when the effect of the diets on body weight and the known effects on sex-specific P-450 isoenzyme expression are compared, these effects suggest a mechanism for the action of CR. By comparative analysis, the effect of CR on tumor pathology suggests that the same mechanisms responsible for inhibiting reproduction may be responsible for delaying the aging-related increase in incidence of diseases. Based on these data, the adaptive/longevity-related process theory of CR is modified to incorporate aspects of the disposable soma theory of aging, as well as pleiotropism.