In the June 5 issue of Cell Stem Cell an article was published that described regeneration of the immune system by fasting. According to the lead author, Valter Longo both animal experiments and work with humans showed that with prolonged fasting the white blood cell count in the blood went down. But when food was started again the missing white blood cells came back.
In other experiments the group has shown that with starvation an enzyme, called PKA is lowered, which triggers the hematopoietic stem cells responsible for the production of white blood cells. Previously the research team has examined the life span of simple organism and found that a lowered PKA level was responsible for an extended life span in these species. Dr. Longo explained in that in humans with fasting and the lowering of PKA the body rids itself of damaged or old parts of the immune system. Possible applications for this discovery would help persons who have undergone chemotherapy or other person who have aged to rid themselves of old cells that would be more prone to turn cancerous down the road. When food intake starts again, the bone marrow stem cells get stimulated to produce new immune cells. The end result is that the person will reemerge stronger and live longer.