Calcium - what is it?
Calcium, New RDA* 800 mg
The human body requires more calcium than any other mineral. At least 99% of the calcium is found in the bones and teeth, giving them strength and rigidity. The remaining 1%, which is in the blood, muscles, and nerves, plays an important role in regulating physiological functions.
Calcium is a white, malleable, metallic element. In the body it is found in various combinations such as calcium carbonate, calcium phosphate, calcium fluoride, and calcium sulphate. Large quantities of fat, oxalic acid, and phytic acid in the food can prevent proper calcium absorption.
Calcium does not exist freely in nature, but occurs abundantly as limestone (CaCO3), gypsum (CaSO4.2H2O), and fluorite (CaF2). Many calcium compounds (e.g. fluorspar and calcium carbonate) are almost insoluble in water, but there are exceptions (e.g. calcium chloride and calcium nitrate).
*Sourced from EFSA WEBSITE
Calcium - what does it do?
Important for the formation and maintenance of strong bones and teeth, as well as the functioning of nerves and muscles. It is also involved in blood clotting.
In the vertebrate skeleton, calcium provides rigidity in the form of calcium phosphate (Ca10(OH)2(PO4)6, also known as hydroxyapatite), embedded in collagen fibrils. Calcium is also a key component in the maintenance of cell structure. Membrane rigidity, viscosity and permeability are partly dependent on local calcium concentrations. Calcium fulfils important physiological roles as a cofactor for many enzymes (e.g. lipase), as an important component of the blood clotting mechanism and through an active role as an intracellular signal. Changes in intracellular calcium concentration, in response to a physiological stimulus, such as a hormone or neurotransmitter, can act as an intracellular signal. This signalling controls events such as cell aggregation, muscle contraction and cell movement, secretion, transformation and cell division, as well as muscle protein degradation.
Deficiency
A negative calcium balance occurs when net calcium absorption fails to compensate for urinary calcium losses. Calcium absorption is impaired in individuals with conditions of fat malabsorption (e.g. in syndromes such as pancreatic insufficiency, bile duct obstruction and coeliac disease) because of the lack of vitamin D as a transporter. Acute hypocalcaemia is frequently seen following parathyroid surgery and may occur during thyroid surgery through inadvertent interference with the parathyroid glands. The possible effects of calcium deficiency are numerous and wide-ranging. Signs of calcium deficiency are manifest in the bones and teeth of all young animal species, including humans. Effects include stunted growth, poor quality bones and teeth, and bone malformation.
Calcium - Sources
Milk, cheese and other dairy products, some green leafy vegetables such as broccoli, fortified soya bean products and bread.
