Calcium is the most common mineral in the human body. While best known for its role in maintaining strong bones, calcium carries out many critical functions in the human body.
As an intracellular messenger, calcium facilitates the constriction and relaxation of blood vessels and muscles. It also plays a role in the transmission of nerve impulses and the secretion of hormones, like insulin.
Calcium levels in the blood and fluid surrounding the cells must be maintained within a very narrow concentration range for normal functioning. Because calcium is so vital to survival, the body will leach calcium from the bones (demineralize) to maintain normal blood calcium levels.