Vaughan et al. (1) have published an article in this journal to explain why the two studies on diet restriction in macaques have provided very different results: no life-span increase in the diet-restricted group in Mattison et al. (2), and an increase in Colman et al. (3,4). The differences between the two studies have been stressed (5,6). Particularly, the control group of Colman et al. (3,4) was fed ad libitum a “typical Western modern diet rich in refined and processed foods” (5). A diet “more similar to the traditional Mediterranean or Japanese diet” (5) was portioned to prevent obesity in the control group of Mattison et al. (2). Vaughan et al. (1) also list these differences and conclude that “the contradictory findings are most likely due to methodological differences”. However, it seems possible to go a step further than Vaughan et al. (1) and to clearly assert that diet restriction does not increase life span in macaques: the observed increase in one study is maybe, if not only, due to a bad diet in the control group. In the study showing no effect of diet restriction (2), females lived for 28 years and males for 35 years, while control monkeys lived for 26 years and diet-restricted ones for 29 years in the study reporting a life-span increase (3,4). Furthermore, the old control monkeys of this latter study appeared to be in a poor health (pictures in (3) and (7)), in sharp contrast with monkeys of Mattison et al. (2) (pictures in (8)), for which there was no clear effect of diet restriction on the first occurrence of age-related diseases (see Figure 3b in (6)). Thus, taking into account the low life span and appearance of the control animals of Colman et al. (3,4), both in sharp contrast with the results of Mattison et al. (2), it seems possible to conclude that diet restriction increases life span of macaques only if the control group has a short life span, because of a suboptimal diet in this control group. A hypothesis to explain why diet restriction can increase life span in some species, such as short-lived rodents, and not in other ones, such as long-lived primates, has been published elsewhere (9). Thus, these studies on macaques do not show that diet restriction increases life span in primates, but more probably that poor health and premature deaths are avoided when animals are offered a better diet. Although these results are of importance, particularly in a country like the United States suffering from a huge obesity epidemic probably linked to junk food, they do not seem to offer clues for increasing life span in people favoring a better diet. Vaughan et al, (1) wrote that “it would be convenient to suggest that one study was right and the other flawed and thus put an end to the debate on whether CR (calorie restriction) works in primates”. Because diet restriction “works” in one study and not in the other one, the “flawed study” is probably considered by many readers as the study that does not “work”. However, it seems possible to conclude the opposite: diet restriction does not work in primates and the study showing positive results is explained by a bad diet in the control group. Indeed, avoiding the Super Size me way of life is probably the first step to live long. Diet restriction studies in monkeys are useful to understand the deadly consequences of obesity and of junk food, but are of no help to increase life span or health span of people feeding on an appropriate diet. References 1. Vaughan KL, Kaiser T, Peaden R, Anson RM, de Cabo R, Mattison JA. Caloric restriction study design limitations in rodent and nonhuman primate studies. J Geront Biol Sci Med Sci . 2017. 2. Mattison JA, Roth GS, Beasley TMet al. Impact of caloric restriction on health and survival in rhesus monkeys from the NIA study. Nature . 2012; 489: 318– 321. doi: 10.1038/nature11432 Google Scholar CrossRef Search ADS PubMed 3. Colman RJ, Anderson RM, Johnson SCet al. Caloric restriction delays disease onset and mortality in rhesus monkeys. Science . 2009; 325: 201– 204. doi: 10.1126/science.1173635 Google Scholar CrossRef Search ADS PubMed 4. Colman RJ, Beasley TM, Kemnitz JW, Johnson SC, Weindruch R, Anderson RM. Caloric restriction reduces age-related and all-cause mortality in rhesus monkeys. Nat Commun . 2014; 5: 3557. doi: 10.1038/ncomms4557 Google Scholar CrossRef Search ADS PubMed 5. Cava E, Fontana L. Will calorie restriction work in humans? Aging (Albany NY) . 2013; 5: 507– 514. doi: 10.18632/aging.100581 Google Scholar CrossRef Search ADS PubMed 6. Mattison JA, Colman RJ, Beasley TMet al. Caloric restriction improves health and survival of rhesus monkeys. Nat Commun . 2017; 8: 14063. doi: 10.1038/ncomms14063 Google Scholar CrossRef Search ADS PubMed 7. Wade N. Dieting monkeys offer hope for living longer. New York Times , p. A1. http://www. nytimes.com/2009/07/10/science/10aging.html. Accessed August 23, 2017. 8. Austad SN. Ageing: Mixed results for dieting monkeys. Nature . 2012; 489: 210– 211. doi: 10.1038/nature11484 Google Scholar CrossRef Search ADS PubMed 9. Le Bourg E. The somatotropic axis may not modulate ageing and longevity in humans. Biogerontology 2016; 17: 421– 429. doi:10.1007/s10522-015-9632-6 Google Scholar CrossRef Search ADS PubMed © The Author(s) 2017. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail: email@example.com.
The Journals of Gerontology Series A: Biomedical Sciences and Medical Sciences – Oxford University Press
Published: Mar 1, 2018
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