Reducing Calories in Diet Results in Longer,
Healthier Life Say Monkey Researchers
During 20-year study, half the animals permitted to
eat freely have survived, while 80% given the same diet, but with 30%
fewer calories are still alive
Rhesus monkeys, left to right, Canto, 27, on a
restricted diet, and Owen, 29, a control subject on an unrestricted
diet, are two of the oldest surviving subjects in a pioneering long-term
study of the links between diet and aging in Rhesus macaque
monkeys, which have an average life span of about 27 years in
captivity.
Photo: Jeff Miller /University of Wisconsin-Madison
July 10, 2009 - Consuming
fewer calories leads to a longer, healthier life. That is the conclusion
of scientist who have conducted a decades-long study of monkeys who have
lived most of their lives on a restricted diet.
Writing today in the journal Science, a team
of researchers at the University of Wisconsin-Madison, the Wisconsin
National Primate Research Center and the William S. Middleton Memorial
Veterans Hospital reports that a nutritious but reduced-calorie diet
blunts aging and significantly delays the onset of such age-related
disorders as cancer, diabetes, cardiovascular disease and brain atrophy.
We have been able to show that caloric restriction
can slow the aging process in a primate species, says Richard Weindruch,
a professor of medicine in the UW-Madison School of Medicine and Public
Health who leads the National Institute on Aging-funded study.
We observed that caloric restriction reduced the
risk of developing an age-related disease by a factor of three and
increased survival.
During the 20-year course of the study, half of the
animals permitted to eat freely have survived, while 80 percent of the
monkeys given the same diet, but with 30 percent fewer calories, are
still alive.
Begun in 1989 with a cohort of 30 monkeys to chart
the health effects of the reduced-calorie diet, the study expanded in
1994 with the addition of 46 more 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 those, 13
are given free rein at the dinner table, and 20 are on a
calorie-restricted diet. Rhesus macaques have an average life span of
about 27 years in captivity. The oldest animal currently in the study is
29 years.
The new report details the relationship between
diet and aging, according to Weindruch and lead study author Ricki
Colman, by focusing on the bottom-line indicators of aging: the
occurrence of age-associated disease and death.
In terms of overall animal health, Weindruch notes,
the restricted diet leads to longer lifespan and improved quality of
life in old age. There is a major effect of caloric restriction in
increasing survival if you look at deaths due to the diseases of aging,
he says.
The incidence of cancerous tumors and
cardiovascular disease in animals on a restricted diet was less than
half that seen in animals permitted 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, weve seen the complete prevention of
diabetes, says Weindruch.
In addition, the brain health of animals on a
restricted diet is also better, according to Sterling Johnson, a
neuroscientist in the UW-Madison School of Medicine and Public Health.
It seems to preserve the volume of the brain in
some regions. Its 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.
Brain scans of two Rhesus macaque monkeys
illustrate the findings of a landmark study of diet and aging. The image on the left shows the brain
of an animal allowed free rein at the dinner table (control), while the
image on the right shows the brain of a monkey that for two decades has
been on a nutritious but reduced-calorie diet. The brain of the animal
allowed to eat freely has less tissue volume and more fluid (bright
areas) than the brain of a monkey on the low-cal diet. The images
suggest less brain atrophy or cell loss with aging for animals that
consume a diet with 30 percent fewer calories than if they were
permitted to eat as much as they like. Photo: Courtesy of Sterling C. Johnson/University
of Wisconsin-Madison
In particular, the regions of the brain responsible
for motor control and executive functions such as working memory and
problem solving seem to be better preserved in animals that consume
fewer calories.
Both motor speed and mental speed slow down with
aging, Johnson explains. Those are the areas which we found to be
better preserved. We cant 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.
Such an observation, however, is novel, according
to Weindruch. The atrophy or loss of brain mass known to occur with
aging is significantly attenuated in several regions of the brain.
Thats a completely new observation.
Since the first studies of caloric restriction in
rodents in the1930s, scientists have been intrigued by evidence that
reducing calories can effectively extend lifespan. Such studies have
been undertaken in a number of different animal species ranging from
spiders to humans
The Wisconsin rhesus macaque study, however, is
likely to provide the most detailed insight into the phenomenon and its
potential application to human health as it has tracked in greatest
detail the diets and life histories of an animal that closely resembles
humans. Because people are much longer lived than rhesus monkeys, and no
similar comprehensive study with human subjects is under way, conclusive
evidence of the effects of the diet on human lifespan and disease may
never be known.
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