That a calorie restricted diet can prolong life is a widespread notion. Now, a large study on monkeys confirms this notion and thereby settles a persistent scientific controversy.
Research have indicated that caloric restriction (CR) can lead to a longer and healthier life in animals. Research on fasting has also indicated benefits to health and longevity, increasing autophagy, which in turn appears to be protective against neurodegeneration, cancer, and also ups the immune defense.
However, these studies have mainly been done on animals such as fish, chickens, and mice. Researchers first noticed that rats who had been deprived of food appeared to live longer than their well-fed brethren back in the 1930s. This was the first evidence showing that aging is a biological process that can be altered. Then, studies on yeast produced similar results, strengthening the notion that caloric intake is linked to longevity and health.
Two studies done in the 1980s were the first be done on our primate relatives. These studies on rhesus macaques were designed with the aim to find out if CR could give larger animals a longer and healthier life. One of the studies concluded that this was indeed the case, while the other study landed in the conclusion that yes, the monkeys became healthier, but they did not live longer.
The same research groups have now made a new attempt to find out why they initially landed at different conclusions. Researchers at the University of Wisconsin-Madison and the National Institute on Aging constructed a new comprehensive study that shows that CR can indeed improve health, survival, and increase longevity in rhesus monkeys.
They show that a reduction of 25 percent of calorie intake each day, reduce the risk of various diseases, and thus, live longer. These diseases are especially type-2 diabetes, various cancers, and cardiovascular disease. The researchers also found that the less healthy food consumed by the monkeys, the more the benefits were from eating a calorie restricted diet.
The different groups of monkeys were fed two different diets, one group at the University of Wisconsin-Madison were feed a typical so-called Western diet, with a higher portion of sugar and fat. Another group of monkeys at the National Institute on Aging in Maryland got to eat more nutritionally dense food, containing more fibers, vitamins, and minerals.
Perhaps not so surprising, the group that ate the less healthy ‘Western diet’ gained more from calorie restriction than the group that ate a more varied and nutritionally dense diet.
But in absolute terms, the monkeys that ate a healthy diet and a calorie-restricted diet lived the longest. CR added a few years to these macaque’s lifespan and those monkeys that began eating a calorie restricted diet from a young age gained the most from it.
The researchers found that moderate CR was effective, but more severe reductions of food intake were not associated with additional benefits to the monkeys’ health. A 20 percent reduction of calories was considered a mild restriction, 30 percent as moderate, and 50 percent was a severe restriction.
The University of Wisconsin-Madison trial showed that the monkeys lived significantly longer than the controls; the males on CR diets lived about two years longer, while females on CR diets lived about six years longer. The CR primates also exhibited lower rates of cancer and heart disease.
This kind of research method is very difficult to apply to people for a variety of reasons, both ethical and scientific. Humans live much longer, increasing the scope and it is hard to precisely control what people eat, then limited by the ethical dilemma of not controlling what people eat.
Population studies can provide clues, however. This type of cohort study gathers large amounts of data on how different populations live in relation to each other when it comes to aging, diseases, and diet. These studies have shown that a diet rich in nuts, vegetables, and fish, seems to be the best to avoid the typical age-related diseases.
The new study on the monkeys confirms what is seen in population studies in humans. That a little extra fat was good for the female monkeys. That the female monkeys lived longer if they had slightly more fat on the body than the male monkeys.
The findings by the collaboration between the University of Wisconsin-Madison and the National Institute on Aging has been published in the journal Nature Communications.
Julie A. Mattison et al. Caloric restriction Improves health and survival of rhesus monkeys. Nature Communications, 2017. DOI: 10.1038 / ncomms14063
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