Working with rhesus monkeys for 20 years, researchers at the University of Wisconsin-Madison have found that severely restricting calories led to significantly fewer deaths from natural causes as well as fewer cases of diabetes, cancer, cardiovascular disease and brain shrinkage.
The research, to be published Friday in the journal Science, is the most extensive, rigorous study to date to test the concept known as caloric restriction in a higher species of mammal. A typical caloric restriction regimen involves eating a highly nutritious diet with about 30% fewer calories than normal – or a drop to 1,400 calories a day for a person who usually takes in 2,000 calories.
For years, the concept has fascinated scientists looking for ways to slow aging. Studies on subjects ranging from guppies to dogs consistently have shown that reducing calories by about a third results in a similar increase in longevity.
But UW’s research has been closely followed because it represents a long-term, controlled experiment on our closest relatives.
“This is an extremely important paper,” said Luigi Fontana, an associate professor of medicine at Washington University in St. Louis.
He noted that the researchers found a big reduction in cardiovascular and cancer mortality as well as a slowing of aging in the brain.
That’s especially important, given that the monkeys already were consuming a healthful diet that was low in saturated fat, trans fat and cholesterol.
“If we transpose this effect to humans who are eating a typical high-fat Western diet, the effect most likely would be much greater,” said Fontana, who was not a part of the study.
The UW study was started in 1989 with 30 monkeys and expanded in 1994 with 46 more monkeys. When the monkeys were put into the study, they were from 7 to 14 years old. A rhesus monkey in captivity has an average life span of about 27 years. The average age of the monkeys in the study now is about 26.
Of the 76 monkeys, 37% of those eating a normal diet died of age-related causes, compared with 13% of those on the calorie restricted diet.
There was a 50% reduction in both cardiovascular disease and cancer in the monkeys on the restricted diet. In addition, 16 of the control animals developed diabetes or became pre-diabetic, compared with none of the calorie-restricted animals.
“We see a complete prevention of diabetes,” said lead author Ricki Colman, an associate scientist at UW.
In a surprising development, the researchers also found that the restricted monkeys had less loss of brain cells in areas of the brain involved in motor control, complex thinking and short-term memory. However, although their brain scans looked better, there has been no finding that the restricted monkeys have improved brain function.
The restricted monkeys are leaner, with less muscle loss and more fat loss. They also look younger when viewed next to a similarly aged monkey that has been allowed to eat a full diet.
But are they happier?
“There are animals that are always crabby and animals that always seem to be happy,” Colman said. “That’s a challenging thing to evaluate.”
Colman noted that the restricted monkeys are a lot more active in preparation of feeding and tend to eat their food immediately. The unrestricted monkeys will take their time and consume their food throughout the day.
There are a variety of explanations for how caloric restriction improves health, including a reduction in inflammation, protection against oxidative stress in the body and changes in brain-hormonal systems.
A theory that has gotten more attention in recent years suggests that caloric restriction tricks the body to go into a stage of low-intensity stress that, in turn, leads to the production of substances that protect against more intense disease-causing stress.
Of course, the bigger question is whether calorie restriction will prevent disease and extend life in humans, and, if it does, would large numbers of humans be able to stick to a caloric-restriction routine?
The UW researchers acknowledge that the answers to those questions may never be known.
But the study’s findings bring great credibility to research done in lower species and strongly suggest that caloric restriction would be beneficial in humans, said Andrew Dillin, a researcher with the Salk Institute who wasn’t involved with the UW research.
Fontana said there is an extraordinary overlap in the genes, physiology and metabolism of monkeys and humans, suggesting the benefits would apply to humans.
In some of his own research involving small numbers of people who were practicing caloric restriction, Fontana has found a variety of beneficial effects, including protection against obesity, Type 2 diabetes, high blood pressure and artery disease.
He noted that as life expectancy has increased in developed countries over the last century, the burden of chronic age-related diseases has become staggering and likely will be catastrophic.
Caloric restriction could be a powerful tool to help prevent those diseases and promote healthy aging, he said.
In addition, researchers are looking at the possibility of developing a medicine that mimics the effects of caloric restriction.
UW’s study was funded in part by the National Institutes of Health and Middleton Memorial Veterans Hospital in Madison.
Richard Weindruch, the study’s senior author, is co-founder of LifeGen Technologies, a Madison, Wis., company focused on nutrition and genomics, including the effect of diet on aging.
“If we transpose this effect to humans who are eating a typical high-fat Western diet, the effect most likely would be much greater.”
©2009, Milwaukee Journal Sentinel.
Distributed by McClatchy-Tribune Information Services.