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. Superoxide dismutase (SOD) is one of the most important elements of this system. It controls levels of a chemical named “superoxide.” The body manufactures superoxide to kill bacteria and for other uses, but excess levels of superoxide can injure healthy cells. SOD converts superoxide to hydrogen peroxide. Then another enzyme, catalase, neutralizes hydrogen peroxide.

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. During this period, oral SOD became popular as a supplemental antioxidant supplement. Unfortunately, the results of several large studies tended to dash these hopes. Compared to ordinary antioxidants, SOD suffers from the additional disadvantages of being expensive and poorly absorbed when taken by mouth.

SOD is not an essential nutrient, and it is not obtained through food.