For 75 years, scientists have been studying ways to increase the lifespan in humans to exceed 100 years. One method previously thought to add years to a person’s life was calorie restriction. However, a recent study may be proving this theory wrong.
Research on rhesus monkeys at the National Institute of Health Animal Center in Maryland began in 1987 and has been continued for more than 20 years. Published in the journal Nature last week, the study followed 121 monkeys of both genders. Some were fed a normal diet while others were fed just 70 percent of their typical diet.
Senior author of the study and gerontologist at the National Institute on aging in Baltimore, Rafael de Cabo, says that this is the closest experts can get to testing whether or not calorie intake makes a difference in human life span.
De Cabo also stated that it was pretty clear which monkeys were on the restricted diet because they were about 25 percent smaller in weight and size compared to those on a normal diet, and they also looked younger.
Now that enough time has lapsed for some of the monkeys to die, scientists have been able to study and compare the reasons behind each death. What they found is something completely opposite of what they expected: Lifespan was not affected but the level of health was.
For the group of monkeys on a restricted diet, researchers found they did not live any longer than those who were on a normal diet. The difference between the two groups, however, was their health.
Of the monkeys not on a calorie restricted diet, six were found to have cancer, which was believed to be the cause of their death. None of the monkeys on the restricted diet were found to have had cancer, and they also saw lower rates of diabetes.
This study actually contradicts another similar study conducted in Wisconsin in 2009, which suggested lower calorie intake in monkeys does in fact contribute years to maximum life span. Scientists aren’t sure how to explain why the new study produced different results than the Wisconsin study, where 13 percent of the monkeys on diets died due to an age-related disease compared with 37 percent of the non-restricted diet monkeys.
There were, however, some differences between the two experiments. The monkeys studied in Wisconsin had diets that contained far more sugar than those in Maryland. And those that weren’t calorie restricted in Wisconsin were able to eat whenever they pleased instead of being on a regular meal plan like those in Maryland.
Steven Austad of the University of Texas Health Science Center at San Antonio suggested that the two studies produced broadly different results that differed in relatively minor ways. “If dietary restriction does increase longevity in monkeys at all, it only does so under very specific conditions,” he said. “It’s not very robust.”