What is NAC (N Acetyl L Cysteine)?, NAC is a derivative of the amino acid L Cysteine, designed to be more stable and bioavailable than regular cysteine on its own., Lets break it down:, Cysteine As I mention in my book, N acetyl cysteine (NAC) is not found in food sources, but in the body, it converts into cysteine. NAC acts as a precursor to glutathione, a powerful Glutathione Reductase(GR) Activity Assay Kit , Package: 50T EA , Laibo Chem orionprodutoscientificos Meno Clinic NAC (N Acetyl L Cysteine): Building Blocks for Glutathione Meno Clinic