Calcium carbonate:IN 170(i)

Origin: Calcium carbonate is a chemical compound with the formula CaCO3.  It is a common substance found in rocks in all parts of the world, and is the main component of shells of marine organisms, snails, coal balls, pearls, and eggshells. Calcium carbonate is the active ingredient in agricultural lime. It is commonly used medicinally as a calcium supplement or as an antacid, but excessive consumption can be hazardous.

Function: As a food additive it is used as an acidity regulator, anticaking agent, stabiliser or colour. It is used in some soy milk and almond milk products as a source of dietary calcium; one study suggests that calcium carbonate might be as bioavailable as the calcium in cow’s milk. Calcium carbonate is also used as a firming agent in many canned or bottled vegetable products.

Characteristics: Calcium carbonate shares the typical properties of other carbonates. Notably:it reacts with strong acids, releasing carbon dioxide. It releases carbon dioxide on heating, called a thermal decomposition reaction, or calcination, to form calcium oxide, commonly called quicklime. Calcium carbonate will react with water that is saturated with carbon dioxide to form the soluble calcium bicarbonate.

Daily intake: Restricted.

Dietary restrictions: Calcium carbonate is widely used medicinally as an inexpensive dietary calcium supplement or gastric antacid. It may be used as a phosphate binder for the treatment of hyperphosphatemia (primarily in patients with chronic renal failure). It is also used in the pharmaceutical industry as an inert filler for tablets and other pharmaceuticals.Calcium carbonate is used in the production of toothpaste and has seen a resurgence as a food preservative and color retainer, when used in or with products such as organic apples or food.

Excess calcium from supplements, fortified food and high-calcium diets, can cause milk-alkali syndrome, which has serious toxicity and can be fatal.  During the past 15 years, it has been reported in women taking calcium supplements above the recommended range of 1.2 to 1.5 g daily, for prevention and treatment of osteoporosis, and is exacerbated by dehydration. Calcium has been added to over-the-counter products, which contributes to inadvertent excessive intake. Excessive calcium intake can lead to hypercalcemia, complications of which include vomiting, abdominal pain and altered mental status.


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