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 NAC vs. Glutathione: Breaking Down the Benefits for Detox, Immunity, and More N Acetyl L Cysteine (NAC) Superior Supplement Products Science First Designs for Health Existing and potential therapeutic uses for N acetylcysteine: The need for conversion to intracellular glutathione for antioxidant benefits ScienceDirect