**1.17 Trace minerals**

Trace minerals act as a cofactor of antioxidant enzymes thus enabling the antioxidant activities to take place. These trace minerals include selenium (Se), zinc (Zn), manganese (Mn), iron (Fe), and copper (Cu) [103]. O2 <sup>−</sup> radicals are eliminated by the enzyme Cu-Zn-SOD and Cu and Zn are the co-factors for the enzyme. One of the enzymes responsible for H2O2 clearance from the cells is CAT and Fe is the essential cofactor of this enzyme. Levels of ferritin may decline with exercise and increasing dietary or supplemental Fe can improve performance. It was shown that moderate-level supplementation of Fe to competitive swimmers increased their performance and helped to maintain normal ferritin levels [107]. Selenium (Se) is a cofactor for the antioxidant enzyme GPx, which is like the enzyme CAT, responsible for removing H2O2 and other organic H2O2 from the cell. A study by Akil et al. [108] showed in rats, that upon acute swimming exercise, lipid peroxidation in the brain was increased and Se supplementation to these rats increased antioxidant activity resulting in inhibition of the free radical production [108]. Manganese (Mn) is a cofactor for the enzyme Mn-SOD. It eliminates O2 <sup>−</sup> radicals produced during oxidative phosphorylation [109].
