From the University of California article by Suzanne Wu
A study in the June 5 issue of the Cell Stem Cell shows that cycles of prolonged fasting protect against immune system damage — a major side effect of chemotherapy — and induces immune system regeneration, shifting stem cells from a dormant state to a state of self-renewal.
Over long periods of not eating significantly, patients on chemotherapy showed lowered white blood cell counts. In mice, fasting cycles “flipped a regenerative switch,” changing the signaling pathways for hematopoietic stem cells, which are responsible for the generation of blood and immune systems.
The study has major implications for healthier aging, in which immune system decline contributes to increased susceptibility to disease. By outlining how prolonged fasting cycles — periods of no food for two to four days at a time over the course of six months — kill older and damaged immune cells and generate new ones, the research also has implications for those with a wide range of immune system deficiencies, including autoimmunity disorders.
Valter Longo, director of the USC Longevity Institute, said, “When you starve, the system tries to save energy, and one of the things it can do to save energy is to recycle a lot of the immune cells that are not needed, especially those that may be damaged. What we started noticing in both our human work and animal work is that the white blood cell count goes down with prolonged fasting. Then when you re-feed, the blood cells come back.”
Fasting cycles
Prolonged fasting forces the body to use stores of glucose, fat and ketones, and it breaks down a significant portion of white blood cells. The effect is likened to lightening a plane of excess cargo.
During each cycle of fasting, this depletion of white blood cells induces changes that trigger stem cell-based regeneration of new immune system cells. In particular, prolonged fasting reduced the enzyme PKA, an effect previously discovered by the Longo team to extend longevity in simple organisms and which has been linked in other research to the regulation of stem cell self-renewal and pluripotency — that is, the potential for one cell to develop into many different cell types. Prolonged fasting also lowered levels of IGF-1, a growth-factor hormone that Longo and others have linked to aging, tumor progression and cancer risk.
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