Findings published in Science indicate that 80 per cent of rhesus monkeys who consumed a calorie restricted diet without being malnourished were still alive after 20 years, compared to only 50 per cent of control animals who ate freely.
"We have been able to show that caloric restriction can slow the aging process in a primate species," said study leader Professor Richard Weindruch from the University of Wisconsin-Madison. "We observed that caloric restriction reduced the risk of developing an age-related disease by a factor of three and increased survival."
Not surprisingly, longevity and enhanced quality of life is the ultimate aim of most research into diet and nutrition, but very few studies actually achieve such a link. The trick now will be to see if it can be carried over to humans - something the researchers say is highly unlikely due to the extremely restrictive nature of such a diet.
“Our data indicate that adult-onset moderate caloric restriction delays the onset of age-associated pathologies and promotes survival in a primate species,” wrote the researchers.
“Given the obvious parallels between rhesus monkeys and humans, the beneficial effects of caloric restriction may also occur in humans. This prediction is supported by studies of people on long-term caloric restriction, who show fewer signs of cardiovascular aging,” they added.
“The effect of controlled long-term caloric restriction on maximal life span in humans may never be known, but our extended study will eventually provide such data on rhesus monkeys.”
The Wisconsin-based researchers started their study in 1989 with 30 rhesus macaques (Macaca mulatta), and subsequently expanded this to 76. The animals were divided into two groups; one was allowed to eat freely (control group), while the other group had their energy intake restricted by 30 per cent.
According to Weindruch and his co-workers, macaques typically live for about 27 years in captivity. All the monkeys were aged between 7 and 14 when introduced into the study, they added.
In addition to increased lifespan in the calorie restriction group, a halving of the incidence of cancer and cardiovascular disease was observed in this group, compared to the control animals.
Furthermore, while free eating resulted in diabetes or impaired glucose regulation no animal on the restricted diet developed these conditions. "So far, we've seen the complete prevention of diabetes," said Weindruch.
Brain health was also better in the animals with restricted calorie diets, said the researchers, particularly the parts of the brain responsible for motor control and executive functions such as working memory and problem solving.
"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," said co-researcher Sterling Johnson.
"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," added Weindruch.
10 July 2009, Volume 325, Pages 201-204
"Caloric Restriction Delays Disease Onset and Mortality in Rhesus Monkeys"
Authors: R.J. Colman, R.M. Anderson, S.C. Johnson, E.K. Kastman, K.J. Kosmatka, T.M. Beasley, D.B. Allison, C. Cruzen, H.A. Simmons, J.W. Kemnitz, R. Weindruch