In the body, dangerous naturally occurring substances called free radicals pose a risk of harm to many tissues. The body deploys an “antioxidant defense system” to hold them in check. Glutathione, a protein made from the amino acids cysteine, glutamic acid, and glycine, is one of the most important elements of this system.

Glutathione does much of its work in the liver, although it is also found elsewhere in the body. Besides fighting free radicals, it helps keep various essential biological molecules in a chemical state called “reduced” (as opposed to “oxidized”). In addition, glutathione can act on toxins such as pesticides, lead, and dry cleaning solvents, transforming them in such a way that the body can excrete them more easily.

Nutrients such as vitamin C and vitamin E also help neutralize free radicals. In the 1990s, such antioxidant supplements were widely promoted for preventing a variety of diseases, including cancer and heart disease. (Unfortunately, this hope has largely floundered as the results of large, reliable studies have come in.) During this period, oral glutathione became popular as an additional antioxidant supplement. Unfortunately, glutathione is not absorbed when taken by mouth, so such supplements are almost certainly useless. It may be possible, however, to raise glutathione levels in the body by taking other supplements, such as vitamin C, cysteine, lipoic acid, and N-acetylcysteine. Whether doing so would offer any health benefits remains unclear.

There is no dietary requirement for glutathione. The body makes it from scratch, utilizing vitamins and common amino acids found in food.

Glutathione levels in the body are reduced by cigarette smoking. Various diseases are associated with reduced levels of glutathione, including cancer, cataracts, diabetes, and HIV infection.1