schwit1 sends word of research showing that cycles of prolonged fasting can both protect the immune system from harm and also induce regeneration by causing stem cells to start renewing themselves. 'In both mice and a Phase 1 human clinical trial (abstract), long periods of not eating significantly lowered white blood cell counts. In mice, fasting cycles then "flipped a regenerative switch," changing the signaling pathways for hematopoietic stem cells, which are responsible for the generation of blood and immune systems, the research showed. "PKA is the key gene that needs to shut down in order for these stem cells to switch into regenerative mode. It gives the OK for stem cells to go ahead and begin proliferating and rebuild the entire system," explained [study author Valter Longo], noting the potential of clinical applications that mimic the effects of prolonged fasting to rejuvenate the immune system. "And the good news is that the body got rid of the parts of the system that might be damaged or old, the inefficient parts, during the fasting. Now, if you start with a system heavily damaged by chemotherapy or aging, fasting cycles can generate, literally, a new immune system."'