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Monkeys live longer after eating lighter: study

July 9, 2009
Courtesy Science
and World Science staff

A 20-year study on rhe­sus mon­keys sug­gests that slashing ca­lorie in­take slows the ag­ing pro­cess and leads to long­er life spans, pos­sibly in hu­mans al­so, re­search­ers say.

Pre­vi­ous stud­ies with yeast, worms, flies, and ro­dents have sug­gested that this kind of “ca­lor­ic re­stric­tion” – a re­duc­tion of about 30 per­cent, and very dif­fer­ent from mal­nu­tri­tion – can lead to such health ben­e­fits in some mam­mals. But giv­en the many par­al­lels be­tween rhe­sus mon­keys and hu­mans, this study sug­gests that these ben­e­fits might oc­cur in hu­mans as well, ac­cord­ing to the sci­en­tists.

Calorie-restric­ted mon­key "Can­to." (Cour­tesy Sci­ence)


Ricki Col­man at the Wis­con­sin Na­tional Pri­mate Re­search Cen­ter and col­leagues be­gan the study in 1989 by as­sign­ing adult rhe­sus mon­keys, each be­tween age sev­en and 14, to ei­ther a ca­lor­ic re­stric­tion group or a con­trol group. 

Once the mon­keys were as­signed, the re­search­ers be­gan re­duc­ing the di­ets of mon­keys in the ca­lor­ic re­stric­tion group by 10 per­cent every three months un­til they reached the de­sired 30 per­cent cut­back. 

At the end of the stu­dy, 37 per­cent of the con­trol group had died of age-re­lat­ed causes while only 13 per­cent of the ca­lor­ic-re­stric­tion group had, they found. This find­ing means that the con­trol mon­keys ex­pe­ri­enced a death rate from age-re­lat­ed con­di­tions such as di­a­be­tes, can­cer, car­di­o­vas­cu­lar dis­ease, and brain at­ro­phy three times that of the ca­lor­ic re­stric­tion group. 

Any mon­key that died during the study un­der­went a com­plete nec­rop­sy by a board-certified path­ol­o­gist, so that age-re­lat­ed deaths could be dis­tin­guished from oth­er un­re­lat­ed con­di­tions, the re­search­ers not­ed. 

The find­ings are to ap­pear in the July 10 is­sue of the re­search jour­nal Sci­ence.

A study in the No­vem­ber 2007 is­sue of the jour­nal An­nals of the New York Acad­e­my of Sci­ences reached si­m­i­lar con­clu­sions about the ben­e­fits of ca­lor­ic re­stric­tion by com­par­ing Amer­i­cans with some Jap­a­nese popula­t­ions with tra­di­tion­ally spare di­ets.


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A 20-year study on rhesus monkeys suggests that substantially reducing caloric intake slows the aging process and leads to longer life spans, possibly in humans also, researchers say. Previous studies with yeast, worms, flies, and rodents have suggested that this kind of “caloric restriction” – a reduction of about 30 percent, and very different from malnutrition – can lead to such health benefits in some mammals. But given the many parallels between rhesus monkeys and humans, this study suggests that these benefits might occur in humans as well, according to the scientists. Ricki Colman at the Wisconsin National Primate Research Center and colleagues began the study in 1989 by assigning adult rhesus monkeys, each between age seven and 14, to either a caloric restriction group or a control group. Once the monkeys were assigned, the researchers determined their original food intake and began reducing the diets of those monkeys in the caloric restriction group by ten percent for three months until they reached the desired 30 percent cutback in calories. At the end of the study, 37 percent of the control group had died of age-related causes while only 13 percent of the caloric-restriction group had, they found. This finding means that the control monkeys experienced a death rate from age-related conditions such as diabetes, cancer, cardiovascular disease, and brain atrophy three times that of the caloric restriction group. Any monkey that died over the course of the study underwent a complete necropsy by a board-certified pathologist, so that age-related deaths could be distinguished from other unrelated conditions, the researchers noted. The findings are to appear in the July 10 issue of the research journal Science. A study in the November 2007 issue of the journal Annals of the New York Academy of Sciences reached similar conclusions about the benefits of caloric restriction by comparing Americans with some Japanese populations with traditionally spare diets.