What does calcium do?

Calcium helps make bones strong. It combines with phosphate and other minerals to form the hard mineral structure that gives bones their stiffness, while collagen provides much of their flexible framework.

Bones are living tissue, not permanent stone. Throughout life, the body continually removes small amounts of old bone and replaces them with new bone in a process called remodeling. Adequate calcium supports this process, especially during childhood and adolescence, when the skeleton is growing. Vitamin D is also important because it helps the intestines absorb calcium from food.

Calcium does more than support the skeleton. Small amounts circulating in the blood help muscles contract, nerves transmit signals, and blood clot normally. If dietary calcium remains too low, the body can draw calcium from bones to maintain these essential functions. Over time, that can contribute to reduced bone density. Dairy products, fortified plant milks, tofu made with calcium, and some leafy greens are common sources, although the amount absorbed varies between foods.