Glutathione: Master Antioxidant, Reducing Oxidative Stress, and Detoxification NAC N Acetyl L Cysteine 120t by Allergy Research Group N Acetyl Cysteine (NAC) 600mg 3X100 Caps Converted to Glutathione NON GMO 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 for thyroid health This is one of my most recommended supplements, because of the numerous important roles it plays in the body, and its impact on multiple body systems.