N-acetyl-L-cysteine (NAC) is the acetylated form of L-cysteine. Compared to L-Cysteine, NAC is generally better tolerated and less sensitive to oxidation. Sulfur-containing amino acids are used for the production of tissues. Cysteine stimulates the production of proteins, glutathione and taurine. Glutathione has been called the ‘master antioxidant’ because of the crucial role it plays in the body’s defenses and reducing antioxidants such as vitamin C, vitamin E, coenzyme Q10 and alpha-lipoic acid in the antioxidant cycle. It also plays a role in the conversion of nutrients in the body and the production of DNA and proteins.