Manganese (Mn) is the 12th most abundant element in the earths crust. The total amount of manganese in the adult human organism has been determined to be about 10-20mg, most of which is found in skeleton, liver, kidney, pancreas and the heart.3 The rest is distributed widely throughout all the tissues and fluids, without notable concentration in any particular location, and with comparatively litde variations among organs or with age. However, manganese concentration tends to be higher in tissues rich in mitochondria than in the cytoplasm or in other organelles of the cell. The number of manganese metalioenzymes is quite limited, whereas the enzymes that can be activated by manganese are numerous. They include hydrolases, kinases, decarboxylases and tranferases, all of which are involved in multitude of metabolic processes, including bone formation, energy production, as well as both in protein and in fat metabolism.