N-Acetyl-L-CysteinePrecursor to GlutathioneSupports Liver & Lung FunctionDietary SupplementN-Acetyl-L-Cysteine (NAC) is a powerful antioxidant amino acid and a precursor in the body to the critical endogenous antioxidant glutathione. Glutathione exerts a variety of protective effects, including detoxification and intracellular defense against oxidative stress. Substances known to reduce glutathione status are acetaminophen and alcohol.