10 July 2009

Monkeys live longer on low-KJ diet

A 20-year study found cutting kilojoules by almost a third slowed the ageing of monkeys and fended off death.

A 20-year study found cutting kilojoules by almost a third slowed the ageing of monkeys and fended off death.

This is not about a quick diet to shed a few kilograms.

Scientists have long known they could increase the lifespan of mice and more primitive creatures - worms, flies - with deep, long-term cuts in what should be normal consumption.

Now comes the first evidence that it delays the diseases of ageing in primates, too - rhesus monkeys living at the Wisconsin National Primate Centre. Researchers reported their study in the journal Science.

What about those other primates, humans? Nobody knows yet if people in a world better known for overeating could stand the deprivation long enough to make a difference, much less how it would affect our more complex bodies. Still, small attempts to tell are under way.

Less disease in kilojoule-restricted monkeys
"What we would really like is not so much that people should live longer but that people should live healthier," said Dr David Finkelstein of the National Institute on Ageing. The Wisconsin monkeys seemed to do both.

"The fact that there's less disease in these animals is striking," Finkelstein said.

The tantalising possibilities of kilojoule restriction date back to rodent studies in the 1930s. But it is a hot topic today among researchers trying to understand the different processes that make our bodies break down with age, so maybe some of them could be delayed or reversed.

Captive rhesus monkeys have an average lifespan of 27 years, so spotting an effect takes a lot longer than in short-lived mice. The newest study involves 76 monkeys - 30 tracked since 1989 and 46 since 1994. They were normal-sized adults eating a normal diet for a captive monkey, a special vitamin-enriched chow plus some fruit treats.

Then researchers at the University of Wisconsin, Madison, assigned half the monkeys to the reduced-kilojoule diet, cutting their daily kilojoules by 30%, but ensuring what they did eat was properly nourishing.

What the study found
So far, 37% of the monkeys who kept their regular diet have died of age-related diseases - compared with just 13% of the kilojoule cut monkeys, a nearly three-fold difference, the researchers reported. A handful of other monkeys died of unrelated conditions, such as injury, not deemed affected by nutrition.

Death was not the only change. The calorie-cut monkeys had less than half the incidence of cancerous tumours or heart disease as the monkeys who ate normally. Brain scans showed less age-related shrinkage in the dieting monkeys. They also retained more muscle, something else that tends to waste with age.

Compare two cage-by-cage photos of the monkeys and the difference is obvious: A 29-year-old monkey happens to be the oldest non-dieting monkey still alive, and a 27-year-old the oldest still-living dieter. Yet the dieting monkey looks many more years younger than his fatter, frumpier neighbour, not just a mere two.

"All these pieces put together provide rather convincing evidence in our view that caloric restriction can slow the aging process in a primate species," said lead researcher Dr Richard Weindruch, a University of Wisconsin professor heading the NIA-funded study.

’Follow common-sense healthy lifestyle’
He contends that somehow the diet change is reprogramming metabolism in a way that slows aging.

The federal government is funding a small study to see if some healthy normal-weight people could sustain a 25% kilojoule cut for two years and if doing so signals some changes that might, over a long enough time, reduce some age-related disease.

But NIA's Finkelstein cautions that people should not just try this on their own; cutting out the wrong nutrients could cause more harm than good. Just follow commonsense healthy lifestyle advice, he said.

"Everyone's obviously looking for the magic pill," and there's not one, Finkelstein said. "Watch what you eat, keep your mind active, exercise and don't get run over by a car." – (Sapa, July 2009)

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