Superoxide dismutase is an antioxidant metalloenzyme found in mammals. There are two isoforms of superoxide dismutase, one requires copper and zinc to function, whereas the other requires manganese. While the copper and zinc isoform is found mainly in the cytosol of the cell, the manganese isoform is found mainly in the mitochondrial matrix. Both superoxide isoforms catalyse the conversion of the superoxide anion to hydrogen peroxide, and in this way superoxide dismutase may protect the cell from lipid peroxidation, because in its absence the superoxide radical could react with hydrogen peroxide and initiate the lipid peroxidation of cell components. Dietary copper, zinc and manganese may be able to increase the activity of superoxide dismutase, particularly in those with suboptimal intakes of these essential trace minerals. Certainly deficiencies of these trace minerals lower the superoxide dismutase activity of cells and allows increased free radical damage to cell components.
Supplements of superoxide dismutase are available and its is often suggested that such supplements are beneficial at raising tissue levels of the enzyme. However, like all enzymes superoxide dismutase is exposed to digestive processes before absorption can occur and as such it is unlikely that the superoxide dismutase in food and supplements survives the digestive process. The ability of superoxide dismutase to be able to increase tissue levels of the enzyme has been tested in mammals, For example, in one study1, mice were fed a control diet or an identical diet with 0.004 % superoxide dismutase. The results of supplementation showed no increase superoxide dismutase activity in the liver, intestine, kidney or blood of the supplemented animals. This data suggests that superoxide dismutase supplements are not effective at raising tissue levels of the enzyme. The best way to increase tissue levels of superoxide dismutase is therefore likely via optimal intakes of zinc, copper and manganese.
Dr Robert Barrington’s Nutritional Recommendation: A number of antioxidant enzymes are available in supplemental form including superoxide dismutase and glutathione peroxidase. However, these supplements are not thought to be hugely effective. For example, high intakes of vitamin C increases cellular glutathione more effectively that supplements of glutathione peroxidase and optimal intakes of zinc, copper and manganese are the best way to increase cellular superoxide dismutase.