L-Glutathione, also known as reduced L-Glutathione, is composed of the amino acids L-cysteine, L-glutamic acid, and glycine. Reduced refers to the non-oxidized form of L-Glutathione. L-Glutathione is a potent antioxidant and works in the liver to protect the body from harmful substances. It also functions as a precursor to glutathione peroxidase, a key antioxidant enzyme, which protects against lipid peroxidation (fats turning rancid).