Calcium is required for strong bones, teeth, and cardiac function. Calcium not only builds strong bones and teeth but maintains bone density and strength. It helps to regulate heartbeat, blood clotting, and muscle contraction. As well as protecting the body from stress, magnesium works with calcium to provide help to these same body systems and participates in more than 50 different biochemical reactions. That's why magnesium is so important to bone formation, nerve and muscle transmission, and energy production.