Glutathione is a tripeptide made up the amino acids gamma-glutamic acid, cysteine, and glycine. The primary biological function of glutathione is to act as a non-enzymatic reducing agent to help keep cysteine thiol side chains in a reduced state on the surface of proteins. Glutathione is also used to prevent oxidative stress in most cells and helps to trap free radicals that can damage DNA and RNA. As individuals grow older, glutathione levels drop, and the ability to detoxify free radicals decreases.