Dietary Restriction and Aging: Historical Phases, Mechanisms and Current Directions

Energy intake restriction (ER) without es sential nutrient deficiency retards aging and extends life span in all species tested so far, and across wide phylo- genetic differences. Historical phases of this model system for studying aging have included modulation of the survival curve, effects on disease susceptibility and effects on phys iological indices of aging; the current phase focuses upon possible mechanisms whereby ER influences such widely diverse phenomena. Mechanistic possibilities include ef fects on the immune system, on basal state and prolifer ation potential, metabolic rate, DMArepair, levels of free radical scavengers, chromatin structure and protein syn thesis and turnover. The ER model may also be useful in analyzing unifactorial versus multifactorial theories of ag ing, and in clarifying the possible significance of physio logical markers that correlate with differences in maximum life spans between species. J. Nutr. 117: 1650-1654, 1987.