Fasting Is Great for Your Body, Researchers Say

Fasting isn't just for blood tests and the religious. New animal and human testing has revealed that cycles of fasting for two to four days can trigger regeneration of new immune cells, while clearing out damaged ones. It even helps protect against the toxic effects of chemotherapy, a new study suggests.

According to the study, published in the journal Cell Stem Cell, prolonged periods of fasting appear to shift adult stem cells in the immune system from a dormant state to a state of self-renewal.

Adult stem cells are the specialized factories of the body, pumping out new cells to replace the old ones in the organs they reside in. Hematopoietic stem cells are a group of adult stem cells that generate blood and immune system cells, renewing the body's ability to fight off toxins and disease.

According to researchers from the University of Southern California (USC), fasting forces the body to use up stored glucose, fat, ketones, and even worn or damaged immune cells. It also appears to activate these hematopoietic stem cells in the body, preparing them to work overtime to replenish the body's immune system.

"What we started noticing in both our human work and animal work is that the white blood cell count goes down with prolonged fasting," co-author Valter Longo said in a statement. "Then when you re-feed, the blood cells come back. So we started thinking, well, where does it come from?"

In a study of fasting mice (deprived of food for two to three days at a time) over six months, it was revealed that worn-out while blood cells died off faster during fasting because the lack of burnable energy causes the body to stop producing PKA - an enzyme that helps prolong cell life.

Researchers explain that this seems to be a purposeful strategy automatically launched by the body. In order to conserve remaining energy during fasting, the body encourages the death of unnecessary or inefficient cells.

The absence of PKA also appeared to trigger the activation of hematopoietic stem cells, preparing them to create new cells once energy supplies are replenished.

"It gives the OK for stem cells to go ahead and begin proliferating and rebuild the entire system," Longo said.

The researchers also found that fasting before chemotherapy helped minimize damage to the immune system inflicted by treatment among humans cancer patients. Phase 1 trials suggested that this occurs simply because the fasting has led to a smaller immune system for the toxic therapy to affect.

The study was published in Cell Stem Cell on June 5.