Calcium is the most abundant mineral in the body and plays a key role in many important functions. It is essential for developing strong bones and teeth, muscle contraction, blood clotting, nerve transmission, and hormone secretion. Approximately 99% of calcium in the body is found in bones and teeth, while the remaining 1% performs critical functions outside the skeletal system. Dietary calcium requirements vary from 800 mg/day for adults to 1.2 g/day for children, and both deficiencies and excesses can impact health. The best dietary sources of calcium include milk, yogurt, cheese, and leafy green vegetables.