Tests on mice suggest that, depending on what you eat and your genetic profile, the method increases the risk of tumors
Intermittent fasting and calorie restriction have been touted as beneficial for health and longevity. Animal experiments in the magazine Naturehowever, suggest that, depending on what you eat immediately after fasting and the individual’s genetic predisposition, the practice may increase the risk of developing tumors in the intestine.
Conducted by scientists at MIT (Massachusetts Institute of Technology), in the United States, the study is the first to analyze changes in intestinal cells not only during food interruption, but in the post-fasting period. The researchers identified that, at this specific moment, when refeeding occurs, there is an intense proliferation of intestinal stem cells, which brings benefits, but also risks to the body, including greater susceptibility to the emergence of tumors.
“Does this mean that intermittent fasting causes bowel cancer? No. Several studies have already demonstrated the benefits of this practice, including for disease prevention. We found in our study that, by increasing the proliferation of stem cells in the intestine, depending on genetic predisposition and, possibly, what one eats after fasting, there may be an increased risk of developing tumors just by fasting. ”says , co-author of the article. He participated in the investigation during a research internship at MIT, with Fapesp.
The results suggest that the practice of intermittent fasting would therefore not be recommended for individuals with a family history of bowel cancer. The finding also sheds light on what to eat after fasting. Therefore, carcinogenic foods – such as processed meat, products rich in sugar and alcoholic beverages – would not be recommended, as they could influence the occurrence of genetic mutations in this most critical period of cell proliferation.
“Although the experiment was carried out with mice, under artificial conditions, it is possible to suggest greater care when carrying out intermittent fasting”says Corrêa, highlighting that more studies on the topic need to be carried out.
Renewal
As the researcher explains, the epithelium, the tissue that internally lines the intestine, renews itself at a very high frequency. In humans, total renewal of the epithelium occurs in 3 to 5 days, for example. The process occurs naturally, through stem cells that, when multiplying and differentiating, are capable of generating all cell types present in the epithelium.
More recently, researchers have understood that stem cell proliferation can be modulated by different factors. In previous work, Corrêa’s group at the Institute of Biology at the State University of Campinas (IB-Unicamp) showed that food – more specifically the consumption of soluble fibers – favors the renewal of the epithelium.
“In addition to regulation by ingested nutrients, we were now able to demonstrate that this proliferation can also be modulated by eating frequency, as in the case of the post-fasting period”explains , professor at IB-Unicamp and co-author of the 2 studies.
“This happens because the cells adapt to the food interruption condition and respond by proliferating more intensely when the animals were fed again after fasting. This has a positive aspect, as it ensures that the epithelium is maintained and recovered. [de um dano ou estresse, por exemplo] more quickly. However, we see a potential risk for the development of more tumors if cancerous mutations occur at this exact moment of greater proliferation.”says Vinolo, who was Corrêa’s doctoral advisor.
In work recently published in Natureresearchers analyzed the proliferation of stem cells in 3 different situations:
- when the animals were fasting;
- when they ate after fasting;
- and when following a normal diet without prolonged eating breaks.
The comparison showed that epithelial stem cells proliferate more intensely during the refeeding period (after 24 hours of fasting).
“Analyzing the mechanism involved, we discovered that the most intense proliferation of stem cells occurs due to the activation of a cellular pathway called mTORC – associated with cellular metabolism and protein synthesis. Basically, with the activation of this pathway, more proteins begin to be produced through the metabolism of polyamines, important molecules for cell division to occur, which results in greater proliferation of stem cells in this feedback period.”explains Corrêa.
In the study, when researchers activated genetic mutations in the post-fasting period, the mice were more likely to develop early-stage intestinal tumors.
“Our finding therefore shows that it is a case of unlucky luck. Intermittent fasting can be very efficient, as it actually reduces calorie consumption. Some research has shown that, in addition to promoting weight loss, the practice reduces the risk of diabetes and can bring improvements to the immune system, protecting the body against some types of cancer. However, we identified that it should not be recommended for everyone, as the time of refeeding is when there is great cell proliferation and can make cells more susceptible to the formation of tumors.”says Corrêa.
The article Short-term post-fast refeeding enhances intestinal stemness via polyamines can be read.
With information from .
