Breaking a fasting brings more health advantages than fasting itself, a study of mice 1 . After the mice had stopped eating, stem cells shot up to repair damage in their intestines - but only when the mice got into their feed again, the study.

This activation of stem cells, however, had its price: mice developed probable precancator polyps in their intestines if they had suffered a carcinogenic genetic change during the post-fasting period than if they hadn't fasted at all.

These results, which were published on August 21 in Nature , show that "Regeneration is not free," says Emmanuelle Passegué, a stem cell biologist at Columbia University Irving Medical Center in New York City, which was not involved in the study. "There is a dark side that needs to be taken into account."

faster away to health

researchers have been investigating the potential health benefits of fasting for decades, and there are indications that practice can help to delay certain diseases and to extend life expectancy in rodents. However, the underlying biological mechanisms behind these advantages were a mystery.

2018 found Ömer Yilmaz, a stem cell biologist at the Massachusetts Institute of Technology in Cambridge, and his colleagues found that stem cells are likely to be involved. During the fasting, these cells begin to burn fat instead of carbohydrates as an energy source, which leads to an increase in their ability to repair damage to the intestines for mice 2 .

yilmaz and his colleagues wanted to understand how and when fasting leads to an increase in stem cell activity and numbers. In their latest work, the researchers examined three mouse groups: animals that fasted 24 hours, those who fasted 24 hours and then were allowed to eat for 24 hours, and those who could eat at any time during the study.

intestinal stem cells increased the fastest in the mice that were given after fasting. These stem cells help to repair and regenerate the intestinal wall by producing large amounts of molecules called polyamines that are important for growth and cell division.

"So much emphasis is placed on fasting and how long it should be fasted, that we have somehow overlooked this whole other side of the equation: what happens in the lined state," says Yilmaz.

downside

Since intestinal stem cells can be a source of precancator due to their ability to share, the animals were rather susceptible to the development of tumors when activating a carcinogenic gene during the refeeding period.

It was these additional cancer fuses that brought the animals to walk across the edge and to move towards the development of tumors, and not the act of eating itself, says Nada Kalaany, specialist for cancer metabolism at the Harvard Medical School in Boston, Massachusetts.

Districts should always be concerned about everything that could cause cancer, but Valter Longo, a biogerontologist at the University of Southern California in Los Angeles, says that mice with the changed genes were "almost convicted of getting cancer", and that the slight increase in the risk that was found in this study may not be generally applicable. So he indicates a study that he published in 2015, in which a 45%reduction in abnormal cell and tissue growth in mice was found, the fasting compared to animals that did not do.

Instead,

Longo says that the results of the Nature study could help identify ways to carry out coordinated cellular regeneration for repairing damaged tissue, as in humans with inflamed intestines or Crohn's disease

It is also unclear whether the results of the Nature study apply to humans and if so, how. Yilmaz says that he and his colleagues do a clinical study to find out. However, the results show that the refeeding period creates a "vulnerable state", which could require additional caution against everything that could damage cellular DNA, he says.