Glutathione is actually 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. There is a direct correlation with the speed of aging and the reduction of glutathione concentrations in intracellular fluids. As individuals grow older, glutathione levels drop, and the ability to detoxify free radicals decreases.

Glutathione is a small molecule found in almost every cell. It cannot enter most cells directly and therefore must be made inside the cell, from its three constituent amino acids: glycine, glutamate and cysteine. The rate at which glutathione can be made depends on the availability of cysteine, which is relatively scarce in foodstuffs.

Glutathione is the major antioxidant produced by the cell, protecting it from 'free radicals' ('oxygen radicals', 'oxyradicals'). These highly reactive substances, if left unchecked, will damage or destroy key cell components (e.g. membranes, DNA) in microseconds. Glutathione recycles other well-known antioxidants such as vitamin C and vitamin E, keeping them in their active state.

Glutathione is a very important detoxifying agent, enabling the body to get rid of undesirable toxins and pollutants. It forms a soluble compound with the toxin that can then be excreted through the urine or the gut.

Glutathione plays a crucial role in maintaining a normal balance between oxidation and anti-oxidation.

Glutathione is required in many of the intricate steps needed to carry out an immune response. For example, it is needed for the lymphocytes to multiply in order to develop a strong immune response, and for ‘killer’ lymphocytes to be able to kill undesirable cells such as cancer cells or virally infected cells.

Glutathione values decline with age and higher values in older people are seen to correlate with better health, underscoring the importance of this remarkable substance for maintaining a healthy, well-functioning body.

Dietary glutathione is found in fresh and frozen fruits and vegetables, fish, and meat. Asparagus, avocado, and walnuts are particularly rich dietary sources of glutathione.