Glutathione Peroxidase: An Antioxidant Enzyme In Health And Disease Selenium Supplementation Improves Glutathione Peroxidase Activity in Alzheimer's Patients Natural Health Research Selenium is one of the few nutrients that directly controls how your body handles oxygen at the cellular level. Every time your cells produce energy, they generate peroxides as a byproduct. That Correlation Between Glutathione Peroxidase Activity and Selenium Concentrations in Both Plasma and Erythrocytes