Immunocal is defined by the Physician's Desk Reference here:
"Immunocal is a U.S. patented natural food protein concentrate in the FDA category of GRAS (generally recognized as safe) which assists the body in maintaining optimal concentrations of glutathione (GSH) by supplying the precursors required for intracellular glutathione synthesis. It is clinically proven to raise glutathione values."
So Immunocal is a nutraceutical, or medicinal food, that raises and sustains your glutathione.
Immunocal is the most effective, safe, and natural way to raise and sustain your glutathione.