Glycine and N acetylcysteine (NAC) are amino acidbased nutrients that serve as precursors for glutathione, one of the body's most important intracellular antioxidants. Glutathione plays a central role in reducing oxidative stress, supporting Glutathione vs. NAC: An Expert Comparison of Antioxidants Transparent Labs Glutathione Synthesis in Cancer Cells Biochemistry (Moscow) Springer Nature Link Glutathione precursor GlyNAC reverses premature aging in people with HIV