Effect of N Acetylcysteine on Sleep: Impacts of Sex and Time of Day 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 All About NAC (N acetylcysteine): What it is and what benefits it has Zenement N acetyl L Cysteine Acetyl L Cysteine (NAC) Antioxidant Support for Detox, Liver & Respiratory Health N ACETYLCYSTEINE (NAC)