Your body uses 99 percent of its calcium to keep your bones and teeth strong, thereby supporting skeletal structure and function. The rest of the calcium in your body plays key roles in cell signaling, blood clotting, muscle contraction and nerve function.
If your body doesn't get enough calcium and vitamin D to support important functions, it takes calcium from your bones. This is called losing bone mass. Losing bone mass makes the inside of your bones become weak and porous. This puts you at risk for the bone disease osteoporosis.