Calcium is needed to develop and maintain healthy bones and teeth, and is an important factor in reducing the rate of age-related bone loss. It is also essential for cellular growth, blood clotting, nerve impulse transmission and muscular function. Calcium can compete with magnesium for absorption, so supplemental magnesium is added. Magnesium in association with Calcium, is important for bone structure and strength, and for keeping calcium soluble. It is also needed for muscle relaxation and for growth. Calcium can also compete with Zinc for absorption, so supplemental zinc is added. Zinc is usually combined in supplemental form with its balancing mineral Copper. Zinc levels are often low in people that have Osteoporosis.