NAC supplies N-acetyl-L-cysteine, a derivative of L-Cysteine, which is more stable and better absorbed than L-Cysteine. NAC functions as a potent antioxidant. As the precursor to glutathione intracellular synthesis, it is essential for the synthesis of glutathione. Glutathione is a critical component of the immune system, as it is an important intracellular water-soluble antioxidant. As part of this function, glutathione plays a vital role as the cofactor for the antioxidant enzymes glutathione peroxidase and glutathione transferase. Glutathione is also important to the liver, as the liver utilizes it for drug detoxification. As a metabolite of cysteine, NAC plays an important role in detoxification, and is hepatoprotective. NAC functions in protecting cells against oxidative stress, and contributes to important bodily reactions.