Calorie restriction doesn’t prolong life in rhesus monkey study

 

Update: New Monkey Study Confirms Calorie Restriction Extends Life!

Do you believe the headlines: Calorie Restriction doesn’t prolong life?

Humans and monkeys are primates. They have many similar physiological traits.  So using monkeys for longevity studies that suggest possibilities for humans is not surprising. The NIA study, recently published in Nature1, reports the unexpected result that a group of rhesus monkeys did not show the life extension effects that have been seen in other studies of calorie-restricted subjects, including animals of the same species. Many issues can be raised about both this study and the other famous rhesus monkey longevity study at the University of Wisconsin, Madison.

First and foremost, though, we must remember that in both cases the monkey subjects are caged animals – primates about as close to human as are available, housed in small wire spaces for their entire lives.  Incarceration is not fun. Human prisoners are well known to have shortened lifespans. So readers should not be shocked that studying caged primates on CR does not produce the same results as the great body of research does that shows that calorie restriction improves health and extends life in all studied species – including free-living humans.

For example, consider this favorite human Calorie Restriction study: elderly Okinawans who limited calories for 60 years by only 11%2. Their life expectancy at age 65 was shown to be the highest in Japan, possibly the world: 

  Females                Males

 89.1 years             83.5 years

A decade of research at the School of Medicine at Washington University in St. Louis further confirms that human calorie restrictors show similar benefits to calorie-restricted animals. Consider this from their 2009 paper3:

… calorie restriction without malnutrition and moderate protein restriction with adequate nutrition may have additional beneficial effects on several metabolic and hormonal factors that are implicated in the biology of aging itself.

Many aspects of the studies include confounding variables:

  • In the University of Wisconsin study, proportionally three times as many control monkeys died of age-related causes compared to the monkeys on Calorie Restriction. The research report in Nature suggest a reason: “Wisconsin monkeys were fed a less healthy diet, which made the calorie-restricted monkeys seem healthier by comparison simply because they ate less of it.4” So are we seeing the effects of lower calories or smaller load of less healthful rations?
  • Many differences besides calorie intake can be observed: “The WNPRC monkeys’ diets contained 28.5% sucrose, compared with 3.9% sucrose at the NIA. Meanwhile, the NIA meals included fish oil and antioxidants, whereas the WNPRC meals was not.5Again, are we seeing the effects of calorie levels, macronutrient ratios, or supplements?
  • The control animals (not eating a Calorie Restriction diet) in the NIA group ate a partially restricted diet: They were given a fixed amount of food, rather than allowing them to eat ad libitum.  So, in a certain way, they were somewhat calorie-restricted and thus any difference in survival between them and their calorie-restricted cage-mates may have been negated.  We have mentioned above the very effective 11% calorie restriction of the traditional Okinawans.6 A 10% calorie-restricted diet  has been also been shown to increase lifespan in laboratory rodents when compared to ad libitum-fed animals.7

 These latter factors are interesting, but we should keep uppermost in mind the first point and recognize that we need more human studies going forward. 

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1 Julie A. Mattison, George S. Roth, T. Mark Beasley3 Edward M. Tilmont, April M. Handy, Richard L. Herbert, Dan L. Longo, David B. Allison, Jennifer E. Young, Mark Bryant, Dennis Barnard, Walter F. Ward1, Wenbo Qi, Donald K. Ingram, Rafael de Cabo. Letter: Impact of caloric restriction on health and survival in rhesus monkeys from the NIA study, Nature, 2012. doi:10.1038/nature11432

2  Willcox BJ, Willcox DC, Todoriki H, Fujiyoshi A, Yano K, et al:

   Caloric Restriction, the Traditional Okinawan Diet, & Healthy Aging.

   Annals of the New York Academy of Science. 2007 Oct;1114:434-55. 

   PMID: 17986602, NIH, NLM, PubMed access to MEDLINE

Fontana L:

Modulating human aging and age-associated diseases.

Biochimica Biophysica Acta. 2009 Oct;1790(10):1133-8. Epub 2009 Feb 10.

   PMID: 19364477,NIH, NLM, PubMed access to MEDLINE

 

4  Maxmen, A. Nature | News: Calorie restriction falters in the long run. Nature. 2012 488 (7413). [Epub ahead of print] http://www.nature.com/news/calorie-restriction-falters-in-the-long-run-1.11297, accessed August 29, 2012

5   Ibid.

6  Willcox et al, op.cit.

7  Duffy PH, Seng JE, Lewis SM, Mayhugh MA, Aidoo A, Hattan DG, Casciano DA, Feuers RJ. The effects of different levels of dietary restriction on aging and survival in the Sprague-Dawley rat: implications for chronic studies. Aging (Milano). 2001 Aug;13(4):263-72. PMID: 11695495, NIH, NLM, PubMed access to MEDLINE

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