An enzyme that catalyzes the conversion of superoxide into hydrogen peroxide and oxygen.SOD has particular value as an antioxidant that can help to protect against cell destruction. It has the distinct ability to neutralize superoxide, one of the most damaging free radical substances in nature. Like so many other protective compounds which naturally occur in the body, it decreases with age, making cells much more vulnerable to the oxidants which cause aging and disease. It occurs naturally in broccoli, Brussels's sprouts, wheat grass and in the majority of green plants. SOD is also marketed as a nutritional supplement.