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Chemical Symbol: Ca
German: Kalzium

1 Definition

Calcium is a bivalent alkaline earth metal with an atomic number of 20 and a medial atomic weight of ca. 40 g/mol.

2 Physiological role

About 90% of the calcium pool in human organism is found in bones as a phosphate in the form of hydroxyapatite (Ca5[PO4]3OH). In this way, calcium ensures stability of the skeleton.

Other important roles of calcium - predominantly in its ionised form Ca2+ - cover coagulation and signal transduction within and outside of cells, thus controlling nerval activity, secretion of hormones and muscular contraction.

In serum, about 50% of calcium stock is bound to proteins, the remainder being in form of ions. The relation is influenced by protein concentration and blood-pH. Serum calcium levels raise in state of acidosis and fall in alkalosis.

3 Nutritional requirements

Calcium is an essential trace element. Daily requirements depend from bone metabolism and amount 800 to 1200 mg per day in adults and at least 1500 mg/day in adolescents, in pregnancy, lactation and postmenopausal period.

Relevant calcium sources are e. g. mild produts, soy, certain vegetables and mineral waters.

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