A study in the June 5 issue of the Cell Stem Cell shows that cycles of prolonged fasting not only protect against immune system damage — a major side effect of chemotherapy — but also induce immune system regeneration, shifting stem cells from a dormant state to a state of self-renewal.

The study has major implications for healthier aging, in which immune system decline contributes to increased susceptibility to disease as people age. 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.

“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.”

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