Reduced Calorie Intake Linked to Longevity and Delayed Disease

A new long-term study has shown that when rhesus monkeys were kept on a nutritious but reduced calorie diet for 20 years, they led a longer, and healthier life with delayed onset of diseases of aging such as cancer, diabetes, cardiovascular disease, and brain atrophy.

Researchers at the Wisconsin National Primate Research Center (Madison, USA) at the University of Wisconsin (UW, Madison, USA) conducted the long-term study, which started in 1989, using rhesus macaques, and focused on the relationship between diet and aging by monitoring the most common indicators of aging, age-associated disease, and death. The researchers started out with 30 rhesus macaques, and added a further 46 more five years later. All the animals joined the study when they were between 7 and 14 years old. Half the animals were allowed to eat freely, while the other half were fed a calorie restricted diet that limited their calorie intake to 30% less of what they would normally eat. The researchers also gave the restricted monkeys vitamin and mineral supplements so they did not become malnourished, and they treated any animals that fell sick. At the end of the study, 33 monkeys were still alive, the oldest 29 years of age. Of these, 20 monkeys continue to be on a calorie-restricted diet.

The results showed that in terms of overall animal health, the calorie-restricted diet led to longer lifespan and improved quality of life in old age. Calorie restriction delayed the onset of age-associated pathologies; incidence of cancerous tumors and cardiovascular disease in monkeys on a restricted diet was under half that seen in those allowed to eat freely. None of the monkeys on the calorie restricted diet developed diabetes, whereas the monkeys that were allowed to eat freely developed impaired glucose regulation or diabetes at the expected rate. Calorie restriction also appeared to preserve the volume of the brain in some regions, in particular the regions used in motor control and executive functions. The study was published in the July 10, 2009, issue of Science.

"Calorie restriction may have an effect on reducing the loss of brain cells,” said coauthor neuroscientist Sterling Johnson, Ph.D. "Motor speed and mental speed usually slow down with aging, but these were the areas of the brain that were better preserved in the calorie restricted monkeys.”

Previous studies on rodents, yeast, and roundworms have already shown that these species live longer when they eat fewer calories. However, this is the first study to show this effect in primates, and is the closest so far to suggest that the same could be true of humans.

Related Links:
Wisconsin National Primate Research Center
University of Wisconsin