Free radicals, unstable oxygen molecules that constantly bombard organs and tissues, arise from everyday activities like breathing and eating. The body counters its negative effects through naturally produced antioxidants, such as superoxide dismutase (SOD). However, several factors (for example, smoking, pollution, drugs, UV light, pesticides) can disrupt the balance and overwhelm the body with too many free radicals, thus resulting in heart disease, cancer, aging, and more than 50 other conditions. Reducing the threat is possible by strengthening and reinforcing the body’s natural levels of SOD through nutritional supplements and a diet rich in antioxidants.
Irwin Fridovich and his graduate student, Joe McCord, made the landmark discovery of the SOD enzyme in 1968, establishing that the body produces its own antioxidants. They developed the “superoxide theory of oxygen toxicity,” which states the superoxide radical inflicts major damage to the body, and SOD, whose primary purpose is to eliminate the destructive radical, is the body’s first line of defense. Fridovich also discovered different types of SOD containing either copper and zinc, manganese, or iron, cofactors necessary for its activity. As of 2009, Fridovich is still involved in SOD research at Duke University.
SOD Food Sources
Knowing SOD’s crucial role in reducing oxidative stress, scientists have been looking for ways to boost its levels through diet. Melons, including honey dew, casaba and cantaloupe, contain the SOD enzyme. Wheat, corn and soy sprouts also have high concentrations of SOD. However, stomach acids and digestive enzymes easily destroy the SOD molecule, leaving effectively no SOD to enter the bloodstream. Fortunately in 1998, European scientists developed a bioavailable form of SOD, GliSODin, derived from melon and protected from digestion by wheat protein. Research on the GliSODin supplement shows it is absorbed into the bloodstream and significantly increases SOD levels.
SOD and Copper/Zinc
Both copper and zinc are necessary for one type of SOD enzyme (CuZnSOD) to function properly in the cell. Regardless of the presence of the SOD molecule, naturally or via GliSODin, if copper or zinc is deficient, then CuZnSOD activity decreases. Foods that are very good sources of both copper and zinc include calf’s liver, crimini mushrooms, spinach, chard, asparagus and sesame seeds.
SOD and Manganese
Found within the cell’s mitochondria, another SOD enzyme is manganese dependent (MnSOD). Regardless of SOD's presence, naturally or via GliSODin, a deficiency of the manganese cofactor results in diminished activity of MnSOD. Foods that are an excellent source of manganese include mustard greens, chard, spinach, romaine lettuce, pineapple, raspberries, strawberries, oats, brown rice and green beans.
External (exogenous) substances that also exhibit antioxidant properties can reinforce SOD and the body’s other internal (endogenous) antioxidant enzymes, glutathione peroxidase and catalase. The most important exogenous antioxidants are vitamin C, vitamin E, and beta carotene (precursor of vitamin A). Although many foods contain some antioxidants, only a few have sufficiently large quantities. Blueberries, strawberries and goji berries are rich in vitamin C. Wheat germ, almonds, and sunflower seeds are some foods with the highest vitamin E content. Carrots, sweet potato and spinach are foods high in beta carotene.