Calcium and Magnesium are essential for proper bone , teeth and muscle development. Both minerals are involved in more than 300 enzymatic reactions which produce energy. Calcium and Magnesium are also necessary for muscle function, providing the mechanism for muscle contraction and relaxation including the heart muscle. Vitamin D helps the body to regulate the transport of calcium from the digestive system through the bloodstream to bone, and assists in the retention of calcium and phosphorous.