Valter Longo, longevity expert at the University of Southern California and colleagues reported that fasting 2 to 4 days in six months can rebuild the immune system.  The study published in the journal Cell Stem Cell shows that fasting can force the body into survival modes to use up stores of fat and sugar and break down old cells and get rid of old and damaged cells and re-generating a new immune system starting from stem cells.  Cancer treatment like chemotherapy and aging as well damages cells and the immune system.  In their study, researchers discovered animals fasting 72 hours before chemotherapy lost fewer white cells indicating that fasting helps the animals to maintain a better immune system.  "Multiple cycles of fasting abated the immunosuppression and mortality caused by chemotherapy and reversed age-dependent myeloid-bias in mice, in agreement with preliminary data on the protection of lymphocytes from chemotoxicity in fasting patients." the researchers reported. (David Liu)

References:

http://www.dailymail.co.uk/health/article-2650456/Fasting-just-eight-days-year-boost-immune-new-study-finds.html

Cheng CW, Adams GB, Perin L, Wei M, Zhou X, Lam BS, Da Sacco S, Mirisola M, Quinn DI5, Dorff TB, Kopchick JJ, Longo VD.  Prolonged fasting reduces IGF-1/PKA to promote hematopoietic-stem-cell-based regeneration and reverse immunosuppression.  Cell Stem Cell. 2014 Jun 5;14(6):810-23.

Safdie F, Brandhorst S, Wei M, Wang W, Lee C, Hwang S, Conti PS, Chen TC, Longo VD.  Fasting enhances the response of glioma to chemo- and radiotherapy.  PLoS One. 2012;7(9):e44603.