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Counting Calories Slows Aging, Disease In Monkeys

Posted on: Thursday, 9 July 2009, 15:05 CDT

A decades-long study of monkeys finds that those who consumed a strict, reduced-calorie diet were three times less likely to die from age-related diseases like cancer, diabetes, heart disease and brain atrophy than monkeys that ate as they liked, researchers reported on Thursday.

"We have been able to show that caloric restriction can slow the aging process in a primate species," said Richard Weindruch, a professor of medicine at the University of Wisconsin in Madison.

"We observed that caloric restriction reduced the risk of developing an age-related disease by a factor of three and increased survival,” he said.

The National Institute on Aging-funded study supports similar findings in research with yeast, worms, flies and rodents, and suggests other primates, including humans, may also benefit from a restricted-calorie diet.

During the 20-year course of the current study, 50 percent of the monkeys permitted to eat as they liked have survived, while 80 percent of the monkeys given the same diet, but with 30 percent fewer calories, are still alive.

The researchers began the study in 1989 with 30 rhesus monkeys, and tracked the health effects of the reduced-calorie diet.  In 1994, the study was expanded to include 46 additional rhesus macaques.  

All of the animals in the study were enrolled as adults at ages ranging from 7 to 14 years.  Today, 33 animals remain in the study, of which 13 eat as they choose and 20 are kept on a restricted calorie diet. 

The average life span of Rhesus macaques is about 27 years in captivity, and the oldest animal currently in the study is 29 years.

The research highlights the relationship between diet and aging by focusing on the "bottom-line indicators of aging: the occurrence of age-associated disease and death,” wrote Weindruch and lead study author Ricki Colman in a report.

In terms of overall health, the restricted-calorie diet led to a longer lifespan and improved quality of life in old age, Weindruch said.

"There is a major effect of caloric restriction in increasing survival if you look at deaths due to the diseases of aging," he said.

For example, incidence of cancer and heart disease in animals on a restricted diet was less than half that seen in animals allowed to eat freely.  

Remarkably, while diabetes or impaired glucose regulation is common in monkeys that can eat all they want, it has yet to be observed in any animal on a restricted diet.

"So far, we've seen the complete prevention of diabetes," said Weindruch.

Furthermore, the brain health of animals that consumed a restricted diet is also better, said neuroscientist Sterling Johnson of the UW-Madison School of Medicine and Public Health.

"It seems to preserve the volume of the brain in some regions. It's not a global effect, but the findings are helping us understand if this dietary treatment is having any effect on the loss of neurons" in aging.

In particular, the areas of the brain responsible for motor control and executive functions such as working memory and problem solving appear to be better preserved in animals that consume fewer calories.

"Both motor speed and mental speed slow down with aging," Johnson said.

"Those are the areas which we found to be better preserved. We can't yet make the claim that a difference in diet is associated with functional change because those studies are still ongoing. What we know so far is that there are regional differences in brain mass that appear to be related to diet."

"The atrophy or loss of brain mass known to occur with aging is significantly attenuated in several regions of the brain. That's a completely new observation,” Weindruch said.

Scientists have been intrigued by the theory that calorie restriction can increase lifespan since initial studies with rodents in the 1930s first showed evidence of the phenomenon. Such studies have since been undertaken in a number of different animal species ranging from spiders to humans.

The Wisconsin study with monkeys, however, is likely to provide the most detailed insight into the phenomenon and its potential application to human health since it has followed in great detail the diets and life histories of an animal that closely resembles humans.

However, because human lifespans are much longer than those of rhesus monkeys, and since no similar comprehensive study with humans is under way, conclusive evidence of the effects of diet on human lifespan and disease may never be known.

The research was published July 10 in the journal Science.

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• University of Wisconsin, Madison
• Science

Source: redOrbit Staff & Wire Reports

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