Iron Supplementation and Physical Performance

Iron is one of the most abundant elements, essential for the completion of numerous important biological functions, including electron transfer reactions, gene regulation, binding and transport of oxygen, regulation of cell growth and differentiation. In the human body it is mainly found in the oxygen transport and storage proteins haemoglobin (Hb) (60 70%) and myoglobin (10%), in various iron-containing enzymes (2%), as well as in the liver, bone marrow and muscle in the form of the storage proteins ferritin (Ferr) and hemosiderin (20 30%) [1]. Only a minor quantity (0.1 0.2%) of total iron, mostly bound to the iron-transport protein transferrin, circulates in the plasma and other extracellular fluids [1, 2]. Besides its essential character, excessive free iron could adversely affect the human body, by augmenting oxidative stress, mainly via the Fenton and Haber-Weiss reactions. Ferritin, hemosiderin and transferrin, assist the system to maintain iron balance under tight control by keeping free iron levels low and hence restrain the conversion of hydrogen peroxide to the highly reactive hydroxyl radical [3] that disturbs cellular homeostasis when it is increased at toxic levels.