These findings include CR-induced attenuation of age changes in plasma triglycerides (2) and melatonin (3) as well as oxidative damage (4) and glucose tolerance (5). Current mortality data from our ongoing studies in rhesus monkeys, although not yet statistically significant, reveal that mortality in CR monkeys is about half of that observed in controls (15% compared with 24%, respectively).

Moreover, because we have already demonstrated that two of the most robust biomarkers of CR in rodents, reduced body temperature and plasma insulin, also occur in rhesus monkeys on CR (2), it became important to assess their association with human survival. CR also slows the rate of decline in serum dehydroepiandrosterone sulfate (DHEAS) such that restricted monkeys maintain more youthful levels of this adrenal steroid (2). DHEAS, which declines in both rhesus monkeys and humans during normal aging, may be important in health maintenance and may serve as another potential longevity marker (6). All three biomarkers indicate that CR causes a fundamental shift in metabolic processes. Figure 1, A to C, shows the effects of