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The US Institute of Medicine (IOM) established Recommended Dietary Allowances (RDAs) for calcium in 1997 and updated those values in 2011. [6] See table. The European Food Safety Authority (EFSA) uses the term Population Reference Intake (PRIs) instead of RDAs and sets slightly different numbers: ages 4–10 800 mg, ages 11–17 1150 mg, ages 18–24 1000 mg, and >25 years 950 mg. [10]
Calcium is also used in maintenance-free automotive batteries, in which the use of 0.1% calcium–lead alloys instead of the usual antimony–lead alloys leads to lower water loss and lower self-discharging. [47] Due to the risk of expansion and cracking, aluminium is sometimes also incorporated into these alloys.
Calcium citrate is recommended for patients with achlorhydria and those on medications that decrease stomach acidity. While calcium carbonate is the most common and least expensive form of calcium and contains 40% of elemental calcium, calcium citrate supplements contain only 21% calcium, requiring more tablets for equivalent dosage.
Calcium regulation in the human body. [6]The plasma ionized calcium concentration is regulated within narrow limits (1.3–1.5 mmol/L). This is achieved by both the parafollicular cells of the thyroid gland, and the parathyroid glands constantly sensing (i.e. measuring) the concentration of calcium ions in the blood flowing through them.
Calcium deposits known as limbus sign may be visible in the eyes. [7] Symptoms are more common at high calcium blood values (12.0 mg/dL or 3 mmol/L). [6] Severe hypercalcaemia (above 15–16 mg/dL or 3.75–4 mmol/L) is considered a medical emergency: at these levels, coma and cardiac arrest can result.
Though calcium is the most plentiful electrolyte in the body, a large percentage of it is used to form the bones. [14] It is mainly absorbed and excreted through the GI system. [14] The majority of calcium resides extracellularly, and it is crucial for the function of neurons, muscle cells, function of enzymes, and coagulation. [14]
Hypocalcemia is a medical condition characterized by low calcium levels in the blood serum. [5] The normal range of blood calcium is typically between 2.1–2.6 mmol/L (8.8–10.7 mg/dL, 4.3–5.2 mEq/L), while levels less than 2.1 mmol/L are defined as hypocalcemic.
The plasma membrane Ca 2+ ATPase (PMCA) is a transport protein in the plasma membrane of cells that functions as a calcium pump to remove calcium (Ca 2+) from the cell. PMCA function is vital for regulating the amount of Ca 2+ within all eukaryotic cells.