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 vs. NAC: Which Antioxidant Is Best for Your Liver? Life Extension Healthy Origins NAC (N Acetyl Cysteine) Healthy Origins N Acetyl Cysteine supplementation lowers high homocysteine plasma levels and increases Glutathione synthesis in the trans sulfuration pathway Italian Journal of Medicine Can N acetylcysteine (NAC) Supplements Increase Cellular Glutathione Glyteine