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 for the Skin Lightening : Benefits & Side Effects IV Drip Glutathione 101, Part 1: Cysteine Misbehaves, But Glutathione Saves The Weston A. Price Foundation Drowning in cysteine Nature Metabolism Glutathione: The Master Antioxidant Core Med Science