Calcium is a major structural element in bones and teeth. Bone is a dynamic tissue that is 'remodeled' throughout life: some bone cells ('osteoclasts') break down bone and release the minerals ('bone resorption'), while other cells ('osteoblasts') produce new bone to replace the bone that was resorbed (1).

 

Calcium is involved in several cell signaling processes: in blood vessels, calcium plays a role in mediating the narrowing ('vasoconstriction') and the relaxation ('vasodilation'). In addition, calcium mediates nerve impulse transmission, muscle contraction, and the secretion of hormones (e.g., insulin) (2).

 

As cofactor, calcium is necessary to stabilize a number of proteins and enzymes, optimizing their activities. The binding of calcium is required for the activation of the vitamin K-dependent blood clotting factors that stop bleeding (3).

 

Calcium concentrations in the blood and fluid that surrounds cells are tightly regulated in order to preserve normal biological function: when blood calcium decreases (e.g., in the case of inadequate calcium intake), a certain hormone (parathyroid hormone) is produced that stimulates the conversion of vitamin D to its active form ('calcitriol'), in the kidneys (4). Calcitriol increases the uptake of calcium from the digestive tract, and stimulates the release of calcium from bone by activating bone resorbing cells ('osteoclasts'); calcium is mobilized at the expense of bone mass. When blood calcium rises to normal levels, the secretion of the parathyroid hormone is stopped and the kidneys begin to excrete any excess calcium in the urine (1).

 

The European Food Safety Authority (EFSA), which provides scientific advice to assist policy makers, has confirmed that clear health benefits have been established for the dietary intake of calcium in contributing to:

 

• the maintenance of normal bones and teeth;
• normal muscle function and neurotransmission;
• normal blood clotting;
• normal energy metabolism;
• the normal function of digestive enzymes;
• normal regulation of cell division and differentiation.