Lipoic acid, also known as alpha-lipoic acid, is a sulfur-containing fatty acid. It is found inside every cell of the body, where it helps generate the energy that keeps us alive and functioning. Lipoic acid is a key part of the metabolic machinery that turns glucose (blood sugar) into energy for the body's needs.

Lipoic acid is an antioxidant, which means that it neutralizes naturally occurring but harmful chemicals known as free radicals. Unlike other antioxidants, which work only in water or fatty tissues, lipoic acid is unusual in that it functions in both water and fat.1,2 By comparison, vitamin E works only in fat and vitamin C works only in water. This gives lipoic acid an unusually broad spectrum of antioxidant action.

Antioxidants are a bit like kamikaze pilots, sacrificing themselves to knock out free radicals. One of the more interesting findings about lipoic acid is that it may help regenerate other antioxidants that have been used up. In addition, lipoic acid may be able to do the work of other antioxidants when the body is deficient in them.3,4

It is thought that certain nerve diseases are at least partially caused by free radical damage. Thanks to its combined fat and water solubility, lipoic acid can get into all the parts of a nerve cell and potentially protect it against such damage. This is the rationale for studies on the potential benefits of lipoic acid for diabetic neuropathy.

A healthy body makes enough lipoic acid to supply its requirements; external sources are not necessary. However, several medical conditions appear to be accompanied by low levels of lipoic acid 5 —specifically diabetes, liver cirrhosis, and atherosclerosis —which suggests (but definitely does not prove) that supplementation would be helpful.

Liver and yeast contain some lipoic acid. Nonetheless, supplements are necessary to obtain therapeutic dosages.