Glutathione is a protein found in most living organisms, including humans, that prevents damage to cells by reacting with oxidizing molecules in the body such as hydrogen peroxide and heavy metals. When it contacts an oxidizing agent, it undergoes a chemical reaction that absorbs any free electron that might otherwise damage the cell. Glutathione is recycled by the cell which removes the electron in another reaction, creating more free gluathione. It also plays a role in the creation and repair of DNA and RNA.

Humans can synthesize gutathione from other amino acids, so they do not require any in the diet. Athough it is available from dietary sources, the human body does not absorb much guathione from it due to a lack of pathways for the protein to be absorbed into the body...

Glutathione at Wikipedia