July 16, 2009
Weekly News UpdateCalorie-Restricted Diet Prolongs Life of Rhesus Monkeys
Research conducted with rhesus monkeys and reported in the July 10 edition of the journal Science indicates that consistently consuming a reduced-calorie diet may lead to a prolonged life and better health. The continuing study, begun in 1989, follows two cohorts of rhesus macaque monkeys. One group consumes a calorie-restricted diet, meaning they eat 30 percent fewer calories than would be found in a normal diet. In contrast, members of the second group are allowed free rein in what they eat.
Ricki J. Colman and Richard Weindruch are the two lead scientists involved with the study. Dr. Colman is a project leader at the Wisconsin National Primate Research Center. Dr. Weindruch is a professor of medicine at the University of Wisconsin-Madison School of Medicine and Public Health. The research team also includes researchers from the William S. Middleton Memorial Veterans Hospital.
When the experiment began 20 years ago, 30 rhesus monkeys were involved in the study. In 1994, another 46 rhesus monkeys were added to the experiment. Today, there are 33 rhesus monkeys involved in the study. Of these 33, thirteen can eat what they want and 20 are on a calorie-restricted diet.
Previous studies using mice as a test subject indicated that those mice on a calorie-restricted diet lived 40 percent longer than mice on a normal diet. Results thus far in the rhesus-monkey study indicate that those monkeys on the restricted diet are living longer and have a reduced incidence of diabetes, cancer, heart disease, and brain disease. The restricted-diet monkeys also show better brain health, exhibited by better motor control and faster mental abilities than monkeys in the other group. Typically these two qualities decrease as an organism ages.
Not all scientists are convinced by these results, however. Those critical of the study authors' conclusions question why there is not a significant difference between the death rate in the two groups. These scientists argue that if the group of rhesus monkeys in the restricted-diet group truly were healthier, they would have a significantly decreased death rate. The authors of the research counter that when deaths not directly related to age (such as complications due to anesthesia) are excluded from the statistical analysis, then the difference in death rate is statistically significant.
The scientists involved with this research think that the results of this primate study may apply to humans as well. However, given how difficult it may be to maintain a restricted-calorie diet, some scientists are looking into creating a supplement that could copy the diet's effects. Thus far, resveratrol, a substance found in grapes, has shown the must promise. Much more research is required before any such supplement would be approved or become available to the public, however.