Glutathione is a peptide that contains one amino acid residue each of glutamic acid, cysteine, and glycine that occurs widely in plant and animal tissues and plays an important role in biologic oxidation-reduction processes and as a coenzyme. Glutathione is used in metabolic and biochemical reactions such as DNA synthesis and repair, as well as synthesis of a variety of other proteins and operation of multiple body systems. Glutathione is synthesized by the body and is also present naturally in many foods. It is also available as an oral dietary supplement, although not well absorbed when taken by mouth. Since the body synthesizes glutathione, increased intake of its amino acid precursors is an approach to increase glutathione.