[WHAT IT DOES: With 99 percent of the body's calcium stored in the skeleton and teeth, the main role of the mineral is to help build bones and increase bone density. However, calcium has other functions, too, including helping blood clot and muscles contract. When the body is short on calcium for these purposes, it steals the mineral from your bones.] Unless we constantly replenish our supply of calcium, drop by drop, our bones become thinner from depleting our calcium savings account, ... It's like living off your principal instead of your interest. It's not smart, and it puts you at risk for osteoporosis.