Endocrine Effects of Dietary Restriction and Aging: The National Institute on Aging Study

Calorie restriction (CR) has been shown repeatedly to extend lifespan and reduce the incidence of age-related disease in a variety of animal models. Rhesus monkeys experience many age-related changes in hormone function that parallel those observed in humans and evidence suggests that CR is a safe and effective means for slowing many of these aging changes. In the National Institute on Aging (NIA) long-term study on rhesus monkeys, CR improved glucoregulatory function and disrupted both the thyroid and growth hormone axis, all of which may be important for mediating the effects of CR. Male monkeys experienced delayed puberty. However, data from old females indicated that restriction did not alter hormone levels or cycling—thus, reducing the potential risk of reproductive dysfunction due to lower caloric intake. While it is certainly advantageous to document improved health and longevity, the long lifespan of nonhuman primates dictates the need to develop physiological biomarkers of aging. Dehydroepiandrosterone (DHEA) and melatonin have met criteria as such and CR was shown to attenuate the age-related decline of these hormones in monkeys. This review summarizes selected findings on the hormonal changes elicited by CR in aging rhesus monkeys.