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 N Acetyl L Cysteine (NAC) glutathione precursor Neuro NACET Supplement N Acetyl Cysteine Ethyl Ester 20x Bioavailable Than NAC 600mg 60 Capsules Walmart.com Gluthatione Injection Bightening Soap N A C GLUTATHIONE PRECURSOR 500MG NAC Mark Hyman, MD