«THE DARK SIDE» OF FASTING: the dangers of abstinence
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A new study on mice has shown that specific dietary restrictions can bring not only benefits but also harm to the body. Science has established that fasting can affect the gut by activating stem cells. However, alongside this undoubtedly positive effect comes a negative side: a diet can trigger the development of tumors in precancerous stages. Recent experiments suggest that fasting, in itself, does not offer any unique benefits to the body.
HUNGER ITSELF IS USELESS
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cientists conducted experiments on laboratory mice that were kept on a restricted diet for some time. The results revealed that the period during which the animals were deprived of food brought almost no significant health benefits. However, these benefits became apparent only after the fasting ended.
The absence of food predictably triggered specific regenerative processes in the body. Specifically, stem cells began to activate, and damaged tissues in the intestines started regenerating. But to the scientists’ surprise, the ability to regenerate was not initiated during fasting itself, but precisely when the mice stopped fasting and resumed normal eating.
THE COST OF REGENERATION
Biologist Emmanuelle Passegué, one of the study’s authors, specializes in stem cell research at Columbia University in New York. Commenting on the findings, Passegué states that fasting has a «dark side» that must be considered when deciding to follow diets that involve food restrictions.
In reality, everything comes at a cost, and regeneration is no exception. Laboratory mice had to pay a price for stem cell activation — the risk of developing precancerous growths in the intestines increased sharply. Genetic changes that promote cancer were not observed before the fasting period but began to occur actively once the fasting ended.
IF YOU «SWITCH THE BATTERIES»…
Scientists have studied the impact of fasting on the body for decades, and evidence has indeed been found that it can extend the lifespan of rodents and combat certain diseases. However, for a long time, scientists couldn’t understand how the biological mechanisms behind these processes worked.
Everything changed about six years ago when a group led by biologist Ömer Yilmaz at MIT (Massachusetts Institute of Technology) joined the research on fasting effects. The team unraveled the «mystery of fasting,» discovering that these processes are linked to the role stem cells play in the body.
When a mouse’s body stops receiving food, stem cells virtually ignore carbohydrates and begin to burn fats actively. In other words, they switch the energy source from one to another. This switch, in turn, further stimulates the regeneration of damaged intestines.
WHAT? WHERE? WHEN?
However, Yilmaz’s team didn’t stop there. The scientists already understood that fasting triggers an increase in the quantity and activity of stem cells. But how exactly does this happen, and at what specific moment? To find out, they experimented with three groups of mice. One group fasted for 24 hours. The second group also fasted for 24 hours, but was then immediately allowed to eat. The third group did not fast at all and ate as usual.
By taking measurements, the researchers found that intestinal stem cells multiplied fastest in the second group. Their eating pattern promoted the production of polyamines — molecules essential for cell growth and division. The more polyamines there were, the more intense the regeneration of the intestinal lining became.
According to Yilmaz, today’s popular diets focus too heavily on fasting schedules and intervals. What really matters is paying close attention to what happens during the «refeeding» phase.
FOOD IS NOT DANGEROUS; THE «TRANSITION» IS
Dietitians and their patients should understand that intestinal stem cell regeneration aid comes at a cost. As these cells divide, they supply material for both the regeneration of healthy tissues and the formation of precancerous cells. Scientists discovered this when they activated a cancer-causing gene in the mice from the second group.
The cancer risk in rodents who started eating after fasting was significantly higher than in those who didn’t fast. This suggests that tumor development is influenced not by eating itself, food deprivation, or diet composition but by the process of resuming eating.
MAYBE IT’S NOT SO BAD
Despite concerns among the scientific community about the increased cancer risk in test mice, there are some optimistic perspectives. Not all researchers believe the experiment was conducted correctly.
For instance, gerontologist Valter Longo from the University of Southern California argues that the cancer observed in laboratory mice is due to genetic modifications made by the experimenters and is not connected to food intake or deprivation.
Longo believes that the heightened cancer risk observed in this study might not occur in a different context. He points to earlier studies in which fasting mice showed a 45% reduction in abnormal tissue growth compared to mice that ate usually.
«VULNERABLE STATE»
The degree of risk when coming out of fasting is debatable, but scientists agree on the usefulness of the new study. Its findings have practical applications, helping doctors coordinate cell regeneration to treat conditions like colitis and other diseases. Yilmaz’s group is already preparing for clinical trials, guided by the principle of «no harm.»
They urge caution regarding anything that could damage cellular DNA. The researchers are convinced that their results indicate that the refeeding period after fasting puts the body in a «vulnerable state.» This factor must be carefully considered when choosing a treatment strategy for various illnesses.
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