In rhesus monkeys, diet could not prolong life
Scientists have been dealing with the myth of eternal youth and immortality for centuries. The first step in this direction was taken a few years ago. Researchers extended the lives of mice, worms, fish and flies by reducing calorie intake in the laboratory. In 2008, the maximum age of baker's yeast, which was genetically manipulated, could be extended tenfold. However, recent study results on rhesus monkeys have shown that this effect is not effective in primates. It is becoming increasingly doubtful whether a diet can extend a person's life. Nevertheless, calorie reduction in old age is becoming increasingly popular, especially in the USA.
With rhesus monkeys, starvation did not prolong life in old age
The idea of being able to extend people's lives for years or even make them immortal is fascinating but also scary. Current research results from the "National Institute on Aging (NIA)" in Maryland, however, move this scenario far away. While reduced calorie intake in mice, worms, fish and flies has been shown to prolong animal life, the diet of rhesus monkeys does not seem to work in this regard.
Scientists have been dieting rhesus monkeys for 23 years. They ate 10 to 40 percent fewer calories a day than the normal animal diet. However, as Julie Mattison and her team report in the online magazine "Nature", there was no life-prolonging effect compared to the normal-fed control group. The researchers were nevertheless able to observe an effect of the diet on the metabolism of the animals, which only received fewer calories at an advanced age of 16 to 23 years. The metabolic activity was healthier. Rhesus monkeys live an average of 27 years in captivity. They only reach the age of 40 in exceptional cases. The animals that started dieting very early also suffered from the usual diseases of old age later, since their immune cells functioned better. Another observation by the scientists concerned the male monkeys. These showed delays in maturity and slowed bone growth in response to the diet. In the end, the researchers came to the conclusion that fewer calories in rhesus monkeys do not result in longer lives.
"To believe that simply reducing calories could make such a far-reaching change was remarkable," said gerontologist Don Ingram of Louisiana State University at Baton Rouge in Nature, who wrote the study 30 years ago while at the NIA has conceived.
Life-prolonging effects seem to depend on the reduced diet
The result of the NIA researchers is in direct contrast to previous study results from the National Primate Research Center in Wisconsin (WNPRC). Long-term studies on a possible life-prolonging effect of calorie reduction are also carried out there. The WNPRC scientists concluded that the reduced calorie intake prolongs the life expectancy of the rhesus monkeys. While in the control group of normally fed animals, 76 of the monkeys died of 14 from age-related diseases, there were only five in the diet group. In the NIA study, 24 percent of the animals died in the control group and 20 percent in the diet group. The death rate was therefore approximately the same in both groups.
The difference is in the type of diet
The NIA researchers suspect that the diet of the rhesus monkeys is very different from each other as the reason for the contrary study results. In the WNPRC, the monkeys in the diet group appeared healthier compared to the control group because they received unhealthy food and the diet group ate less of it. In the NIA, on the other hand, the monkeys were given food on a natural basis. For example, the animals in the WNPRC received food that consisted of 28.5 percent granulated sugar, while the NIA food only contained 3.9 percent. Granulated sugar is considered to be beneficial for the development of type II diabetes, a common cause of death in advanced age. In addition to the feed of the WNPRC, the NIA's pet food also contained fish oil and antioxidants. The monkeys in the control group at the WNPRC were also allowed to eat as much as they wanted. Accordingly, their weight was higher than that of the monkeys in the NIA who received a fixed amount of food. Rick Weindruch, gerontologist at the WNPRC and head of study, admits to “Nature”: “All in all, our food was probably not so healthy.”
"Overall, the WNPRC results may have represented an unhealthy control group rather than a long-lived diet group," the researchers write. "When we started this study, it was dogma that a calorie is a calorie," Ingram told Nature. "I think it's clear that the type of calories the monkeys ate made a big difference." (ag)
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