Whey protein is one of the highest quality proteins available. It is quickly digested, and increases fat burning while simultaneously decreasing appetite. Due to its rich content of L-cysteine, whey protein may boost immune response by up to 500%.
A study from Ohio State University reports that whey protein has antioxidant properties that can boost immune response. Researchers looked at whether whey protein could increase concentrations of glutathione and thereby protect against oxidant-induced cell damage in human prostate cells. Glutathione is a potent antioxidant that supports immune function. They found that treatment with whey protein did increase glutathione by 64%, and did help protect the prostate cells.
Whey protein may also be beneficial after vigorous exercise, when immune function is temporarily slowed and protein needs increase. Researchers at the University of Alberta tested whether whey protein supplementation could enhance immune response via increases in glutathione. In this study, taking whey protein did not change glutathione levels in sedentary men; however, researchers did find a dramatic effect in active men. Blood tests taken before and after a 40 km bike ride showed that the ride significantly lowered glutathione levels and thereby lowered immune function in those taking a placebo, but that the glutathione drop was significantly reduced in those taking whey protein.
Sources: Toxicol In Vitro. 2003 Feb;17(1):27-33; Int J Food Sci Nutr. 2004 Mar;55(2):131-41; Fat Wars by B King, Macmillan:2000