Magnesium Oxide (MgO) is an inorganic compound that occurs in nature as the mineral periclase. It is often used as a supplement to prevent and treat low levels of magnesium. Magnesium plays an important role in the replication of DNA, the secretion of parathyroid hormone, which controls bone calcium levels, the function of muscle tissue and the nervous system, and energy production. It also contributes to protein synthesis, electrolyte balance, psychological function and the reduction of tiredness and fatigue.