Calcium (pronounced /ˈkælsiəm/, KAL-see-əm) is the chemical element A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. The term is also used to refer to a pure chemical substance composed of atoms with the same number of protons. Common examples of elements are iron, copper, silver, gold, hydrogen, carbon, with the symbol Ca and atomic number In chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element. In an atom of neutral charge, atomic number is equal to the number of electrons 20. It has an atomic mass of 40.078 amu. Calcium is a soft grey alkaline earth metal The alkaline earth metals are a series of elements comprising Group 2 (Group IIA) of the periodic table: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra). This specific group in the periodic table owes its name to their oxides that simply give basic alkaline solutions. These elements melt at such high, and is the fifth most abundant element by mass in the Earth Earth is the third planet from the Sun. It is the fifth largest of the eight planets in the solar system, and the largest of the terrestrial planets in the Solar System in terms of diameter, mass and density. It is also referred to as the World, the Blue Planet,[note 3] and Terra.[note 4]'s crust In geology, a crust is the outermost solid shell of a rocky planet or moon, which is chemically distinct from the underlying mantle. The crusts of Earth, our Moon, Mercury, Venus, Mars, Io, and other planetary bodies have been generated largely by igneous processes, and these crusts are richer in incompatible elements than their respective mantles. Calcium is also the fifth most abundant dissolved ion in seawater Seawater is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5%. This means that every 1 kilogram of seawater has approximately 35 grams (1.2 oz) of dissolved salts (mostly, but not entirely, the ions of sodium chloride: Na+, Cl−). The average density of seawater at the ocean surface is 1.025 g/ml; by both molarity and mass, after sodium Sodium is a metallic element with a symbol Na (from Latin natrium or Arabic natrun) and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals within "group 1" (formerly known as ‘group IA’). It has only one stable isotope, 23Na, chloride The chloride ion is formed when the element chlorine picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides, magnesium Magnesium is a chemical element with the symbol Mg, atomic number 12 and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the earth's crust by mass, although ninth in the Universe as a whole. This preponderance of magnesium is related to the fact that it is easily built up in supernova stars from a, and sulfate In inorganic chemistry, a sulfate is a salt of sulfuric acid.[1]

Calcium is essential for living organisms In biology, an organism is any living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homeostasis as a stable whole. An organism may either be unicellular (single-celled) or be composed of, as in humans, many billions of cells grouped into specialized, particularly in cell The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of an organism that is classified as living, and is often called the building block of life. Some organisms, such as most bacteria, are unicellular . Other organisms, such as humans, are multicellular. (Humans have an estimated 100 trillion physiology Physiology is the science of the functioning of living systems. It is a subcategory of biology. In physiology, the scientific method is applied to determine how organisms, organ systems, organs, cells and biomolecules carry out the chemical or physical function that they have in a living system, where movement of the calcium ion Ca2+ into and out of the cytoplasm The cytoplasm is the part of a cell that is enclosed within the cell membrane. In eukaryotic cells, the cytoplasm contains organelles, such as mitochondria, which are filled with liquid that is kept separate from the rest of the cytoplasm by biological membranes. The contents of the cell nucleus are not part of the cytoplasm and are instead called functions as a signal for many cellular processes. As a major material used in mineralization of bones and shells, calcium is the most abundant metal A metal is a chemical element that is a good conductor of both electricity and heat and forms cations and ionic bonds with non-metals. In chemistry, a metal is an element, compound, or alloy characterized by high electrical conductivity. In a metal, atoms readily lose electrons to form positive ions (cations). Those ions are surrounded by by mass in many animals Animals are a major group of mostly multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and independently. All animals are also.

Contents

Notable characteristics

Calcium carbonate wetted with hydrochloric acid (thus forming CaCl2) held at a flame and showing red-orange flame color of Ca.

Chemically calcium is reactive and soft for a metal (though harder than lead, it can be cut with a knife with difficulty). It is a silvery metallic element that must be extracted by electrolysis In chemistry and manufacturing, electrolysis is a method of using an electric current to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially highly important as a stage in the separation of elements from naturally-occurring sources such as ores using an electrolytic cell from a fused salt like calcium chloride Calcium chloride, CaCl2, is a common salt. It behaves as a typical ionic halide, and is solid at room temperature. It has several common applications such as brine for refrigeration plants, ice and dust control on roads, and in concrete. The anhydrous salt is also widely used as a desiccant, where it will absorb so much water that it will.[2] Once produced, it rapidly forms a grey-white oxide An oxide is a chemical compound containing at least one oxygen atom as well as at least one other element. Most of the Earth's crust consists of oxides. Oxides result when elements are oxidized by oxygen in air. Combustion of hydrocarbons affords the two principal oxides of carbon, carbon monoxide and carbon dioxide. Even materials that are and nitride In chemistry, a nitride is a compound of nitrogen with a less electronegative element where nitrogen has an oxidation state of −3. Nitrides are a large class of compounds with a wide range of properties and applications coating when exposed to air. It is somewhat difficult to ignite, unlike magnesium, but when lit, the metal burns in air with a brilliant high-intensity red light. Calcium metal reacts with water Water is a ubiquitous chemical substance that is composed of hydrogen and oxygen and is essential for all known forms of life, evolving hydrogen gas at a rate rapid enough to be noticeable, but not fast enough at room temperature to generate much heat. In powdered form, however, the reaction with water is extremely rapid, as the increased surface area of the powder accelerates the reaction with the water. Part of the slowness of the calcium-water reaction results from the metal being partly protected by insoluble white calcium hydroxide Calcium hydroxide, traditionally called slaked lime, hydrated lime, slack lime, or pickling lime, is a chemical compound with the chemical formula Ca2. It is a colourless crystal or white powder, and is obtained when calcium oxide (called lime or quicklime) is mixed, or "slaked" with water. It can also be precipitated by mixing an. In water solutions of acids where the salt is water soluble, calcium reacts vigorously.

Calcium, with a specific mass of 1.55 g/cm3, is the lightest of the alkali earth metals; magnesium (1.74) and beryllium (1.84) are heavier although they are lighter in atomic mass. From strontium on, the alkali earth metals get heavier along with the atomic mass.

Calcium has a higher resistivity than copper Copper is a chemical element with the symbol Cu (Latin: cuprum) and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is rather soft and malleable and a freshly-exposed surface has a pinkish or peachy color. It is used as a thermal conductor, an electrical conductor, a building material, and a or aluminium Aluminium ( ˌæljʊˈmɪniəm , al-yoo-MIN-ee-əm) or aluminum ( /əˈluːmɪnəm/ (help·info), ə-LOO-mi-nəm, see spelling below) is a silvery white and ductile member of the boron group of chemical elements. It has the symbol Al; its atomic number is 13. It is not soluble in water under normal circumstances. Aluminium is the most abundant. Yet, weight for weight, allowing for its much lower density, it is a rather better conductor than either. However, its use in terrestrial applications is usually limited by its high reactivity with air.

Calcium salts are colorless from any contribution of the calcium, and ionic solutions of calcium (Ca2+) are colorless as well. Many calcium salts are not soluble in water. When in solution, the calcium ion to the human taste varies remarkably, being reported as mildly salty, sour, "mineral like" or even "soothing." It is apparent that many animals can taste, or develop a taste, for calcium, and use this sense to detect the mineral in salt licks A salt lick is a salt deposit that animals regularly lick. In an ecosystem, salt/mineral licks often occur naturally, providing the sodium, calcium, iron, phosphorus and zinc required in the springtime for bone, muscle and other growth in deer and other wildlife, such as moose, elephants, cattle, woodchucks, domestic sheep, fox squirrels, mountain or other sources.[3] In human nutrition, soluble calcium salts may be added to tart juices without much effect to the average palate.

Calcium is the fifth most abundant element by mass in the human body, where it is a common cellular ionic messenger with many functions, and serves also as a structural element in bone. It is the relatively high atomic-numbered calcium in the skeleton which causes bone to be radio-opaque. Of the human body's solid components after drying (as for example, after cremation Cremation is the process of reducing human remains to basic chemical compounds in the form of gases and bone fragments. This is accomplished through high temperatures and vaporization. Contrary to popular belief, the cremated remains are not ashes in the usual sense, but rather dried bone fragments that have been pulverized in a device called an), about a third of the total mass is the approximately one kilogram of calcium which composes the average skeleton (the remainder being mostly phosphorus and oxygen).

Occurrence

Calcium is not naturally found in its elemental state. Calcium occurs most commonly in sedimentary rocks Sedimentary rock is one of the three main rock types . Sedimentary rock is formed by deposition and consolidation of mineral and organic material and from precipitation of minerals from solution. The processes that form sedimentary rock occur at the surface of the Earth and within bodies of water. Rock formed from sediments covers 75-80% of the in the minerals calcite Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (Ca , dolomite Dolomite is the name of a sedimentary carbonate rock and a mineral, both composed of calcium magnesium carbonate Ca and gypsum Gypsum is a very soft mineral composed of calcium sulfate dihydrate, with the chemical formula Ca . It also occurs in igneous Igeous rock is one of the three main rock types (the others being sedimentary and metamorphic rock). Igneous rock is formed by magma (molten rock) being cooled and becoming solid. They may form with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. This magma can be and metamorphic rocks Metamorphic rock is the result of the transformation of an existing rock type, the protolith, in a process called metamorphism, which means "change in form". The protolith is subjected to heat and pressure causing profound physical and/or chemical change. The protolith may be sedimentary rock, igneous rock or another older metamorphic chiefly in the silicate minerals The silicate minerals make up the largest and most important class of rock-forming minerals, constituting approximately 90 percent of the crust of the Earth. They are classified based on the structure of their silicate group. Silicate minerals all contain silicon and oxygen: plagioclase Plagioclase is a very important series of tectosilicate minerals within the feldspar family. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a solid solution series, more properly known as the plagioclase feldspar series . The series ranges from albite to anorthite endmembers (with respective, amphiboles Amphibole defines an important group of generally dark-colored rock-forming inosilicate minerals, composed of double chain SiO4 tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Amphiboles crystallize into two crystal systems, monoclinic and orthorhombic. In chemical composition and, pyroxenes The pyroxenes are a group of important rock-forming silicate minerals found in many igneous and metamorphic rocks. They share a common structure consisting of single chains of silica tetrahedra and they crystallize in the monoclinic and orthorhombic systems. Pyroxenes have the general formula XY2O6 (where X represents calcium, sodium, iron+2 and and garnets The garnet group includes a group of minerals that have been used since the Bronze Age as gemstones and abrasives. The name "garnet" may come from either the Middle English word gernet meaning 'dark red', or the Latin granatus , possibly a reference to the Punica granatum ("pomegranate"), a plant with red seeds similar in shape,.

See also Calcium minerals.

Applications

Some uses are:

Calcium compounds

H and K lines

In the visible portion of the spectrum of many stars, including the Sun, strong absorption lines of singly-ionized calcium are shown. Prominent among these are the H-line at 3968.5 Å and the K line at 3933.7 Å of singly-ionized calcium, or Ca II. For the Sun and stars with low temperatures, the prominence of the H and K lines can be an indication of strong magnetic activity in the chromosphere. Measurement of periodic variations of these active regions can also be used to deduce the rotation periods of these stars.[4]

History

Calcium (Latin word calcis meaning "lime") was known as early as the first century when the Ancient Romans prepared lime as calcium oxide. Literature dating back to 975 AD notes that plaster of paris (calcium sulphate), is useful for setting broken bones. It was not isolated until 1808 in England when Sir Humphry Davy electrolyzed a mixture of lime and mercuric oxide. Davy was trying to isolate calcium; when he heard that Swedish chemist Jöns Jakob Berzelius and Pontin prepared calcium amalgam by electrolyzing lime in mercury, he tried it himself. He worked with electrolysis throughout his life and also discovered/isolated sodium, potassium, magnesium, boron and barium. Calcium metal was not available in large scale until the beginning of the 20th century.

Compounds

Calcium, combined with phosphate to form hydroxylapatite, is the mineral portion of human and animal bones and teeth. The mineral portion of some corals can also be transformed into hydroxylapatite.

Calcium hydroxide (slaked lime) is used in many chemical refinery processes and is made by heating limestone at high temperature (above 825 °C) and then carefully adding water to it. When lime is mixed with sand, it hardens into a mortar and is turned into plaster by carbon dioxide uptake. Mixed with other compounds, lime forms an important part of Portland cement.

Calcium carbonate (CaCO3) is one of the common compounds of calcium. It is heated to form quicklime (CaO), which is then added to water (H2O). This forms another material known as slaked lime (Ca(OH)2), which is an inexpensive base material used throughout the chemical industry. Chalk, marble, and limestone are all forms of calcium carbonate.

When water percolates through limestone or other soluble carbonate rocks, it partially dissolves the rock and causes cave formation and characteristic stalactites and stalagmites and also forms hard water. Other important calcium compounds are calcium nitrate, calcium sulfide, calcium chloride, calcium carbide, calcium cyanamide and calcium hypochlorite.

Isotopes

Main article: Isotopes of calcium

Calcium has four stable isotopes (40Ca and 42Ca through 44Ca), plus two more isotopes (46Ca and 48Ca) that have such long half-lives that for all practical purposes they can be considered stable. It also has a cosmogenic isotope, radioactive 41Ca, which has a half-life of 103,000 years. Unlike cosmogenic isotopes that are produced in the atmosphere, 41Ca is produced by neutron activation of 40Ca. Most of its production is in the upper metre or so of the soil column, where the cosmogenic neutron flux is still sufficiently strong. 41Ca has received much attention in stellar studies because it decays to 41K, a critical indicator of solar-system anomalies.

97% of naturally occurring calcium is in the form of 40Ca. 40Ca is one of the daughter products of 40K decay, along with 40Ar. While K-Ar dating has been used extensively in the geological sciences, the prevalence of 40Ca in nature has impeded its use in dating. Techniques using mass spectrometry and a double spike isotope dilution have been used for K-Ca age dating.

The most abundant isotope, 40Ca, has a nucleus of 20 protons and 20 neutrons. This is the heaviest stable isotope of any element which has equal numbers of protons and neutrons. In supernova explosions, calcium is formed from the reaction of carbon with various numbers of alpha particles (helium nuclei), until the most common calcium isotope (containing 10 helium nuclei) has been synthesized.[citation needed]

Nutrition

Main articles: calcium in biology and calcium metabolism
Recommended Adequate Intake by the IOM for Calcium:[5]
Age Calcium (mg/day)
0–6 months 210
7–12 months 270
1–3 years 500
4–8 years 800
9–18 years 1300
19–50 years 1000
51+ years 1200

Calcium is an important component of a healthy diet and a mineral necessary for life. The National Osteoporosis Foundation says, "Calcium plays an important role in building stronger, denser bones early in life and keeping bones strong and healthy later in life." Approximately ninety-nine percent of the body's calcium is stored in the bones and teeth.[6] The rest of the calcium in the body has other important uses, such as some exocytosis, especially neurotransmitter release, and muscle contraction. In the electrical conduction system of the heart, calcium replaces sodium as the mineral that depolarizes the cell, proliferating the action potential. In cardiac muscle, sodium influx commences an action potential, but during potassium efflux, the cardiac myocyte experiences calcium influx, prolonging the action potential and creating a plateau phase of dynamic equilibrium. Long-term calcium deficiency can lead to rickets and poor blood clotting and in case of a menopausal woman, it can lead to osteoporosis, in which the bone deteriorates and there is an increased risk of fractures. While a lifelong deficit can affect bone and tooth formation, over-retention can cause hypercalcemia (elevated levels of calcium in the blood), impaired kidney function and decreased absorption of other minerals.[7] High calcium intakes or high calcium absorption were previously thought to contribute to the development of kidney stones. However, a high calcium intake has been associated with a lower risk for kidney stones in more recent research.[8][9][10] Vitamin D is needed to absorb calcium.

Dairy products, such as milk and cheese, are a well-known source of calcium. Some individuals are allergic to dairy products and even more people, particularly those of non Indo-European descent, are lactose-intolerant, leaving them unable to consume non-fermented dairy products in quantities larger than about half a liter per serving. Others, such as vegans, avoid dairy products for ethical and health reasons. Fortunately, many good sources of calcium exist. These include seaweeds such as kelp, wakame and hijiki; nuts and seeds (like almonds and sesame); blackstrap molasses; beans; oranges; figs; quinoa; amaranth; collard greens; okra; rutabaga; broccoli; dandelion leaves; kale; and fortified products such as orange juice and soy milk. (However, calcium fortified orange juice often contains vitamin D3 derived from lanolin, and is thus unacceptable for vegans.[11] Research has found an association between diets high in animal protein and increased urinary calcium loss from the bones[12][13][14]. A diet high in fruit, vegetables and cereals was demonstrated to result in greater femoral bone mineral density in older men, in comparison to a range of other diets. Diets high in candy were found to result in lower bone density in both men and women [15]. ) An overlooked source of calcium is eggshell, which can be ground into a powder and mixed into food or a glass of water.[16][17][18] Cultivated vegetables generally have less calcium than wild plants.[19]

The calcium content of most foods can be found in the USDA National Nutrient Database.[20]

Dietary calcium supplements

500 milligram calcium supplements made from calcium carbonate

Calcium supplements are used to prevent and to treat calcium deficiencies. Most experts recommend that supplements be taken with food and that no more than 600 mg should be taken at a time because the percent of calcium absorbed decreases as the amount of calcium in the supplement increases.[5] It is recommended to spread doses throughout the day. Recommended daily calcium intake for adults ranges from 1000 to 1500 mg. It is recommended to take supplements with food to aid in absorption.

Vitamin D is added to some calcium supplements. Proper vitamin D status is important because vitamin D is converted to a hormone in the body which then induces the synthesis of intestinal proteins responsible for calcium absorption.[21]

In July 2006, a report citing research from Fred Hutchinson Cancer Research Center in Seattle, Washington claimed that women in their 50s gained 5 pounds less in a period of 10 years by taking more than 500 mg of calcium supplements than those who did not. However, the doctor in charge of the study, Dr. Alejandro J. Gonzalez also noted it would be "going out on a limb" to suggest calcium supplements as a weight-limiting aid.[29]

Prevention of fractures due to osteoporosis

Such studies often do not test calcium alone, but rather combinations of calcium and vitamin D. Randomized controlled trials found both positive[30][31] and negative[32][33][34][35] effects. The different results may be explained by doses of calcium and underlying rates of calcium supplementation in the control groups.[36] However, it is clear that increasing the intake of calcium promotes deposition of calcium in the bones, where it is of more benefit in preventing the compression fractures resulting from the osteoporotic thinning of the dendritic web of the bodies of the vertebrae, than it is at preventing the more serious cortical bone fractures which happen at hip and wrist.

Possible cancer prevention

A meta-analysis[31] by the international Cochrane Collaboration of two randomized controlled trials[37][38] found that calcium "might contribute to a moderate degree to the prevention of adenomatous colonic polyps".

More recent studies were conflicting, and one which was positive for effect (Lappe, et al.) did control for a possible anti-carcinogenic effect of vitamin D, which was found to be an independent positive influence from calcium-alone on cancer risk (see second study below) [39].

Overdose

Exceeding the recommended daily calcium intake for an extended period of time can result in hypercalcemia and calcium metabolism disorder, as well as kidney stones.

See also

Notes

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  3. ^ M. G. Tordoff. "Calcium: Taste, Intake, and Appetite". Physiological Reviews 81 (4): 1567. http://physrev.physiology.org/cgi/content/full/81/4/1567.
  4. ^ Staff (1995). "H-K Project". Mount Wilson Observatory. http://www.mtwilson.edu/hk/. Retrieved 2006-08-10.
  5. ^ a b "Dietary Supplement Fact Sheet: Calcium". http://ods.od.nih.gov/factsheets/calcium.asp.
  6. ^ "Osteoporosis Prevention - Calcium Recommendations". http://www.nof.org/prevention/calcium2.htm.
  7. ^ Standing Committee on the Scientific Evaluation of Dietary Reference Intakes, Food and Nutrition Board, Institute of Medicine (1997). Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D and fluoride. Washington DC: The National Academies Press. ISBN 0309064031.
  8. ^ Curhan, Gc; Willett, Wc; Rimm, Eb; Stampfer, Mj (Mar 1993). "A prospective study of dietary calcium and other nutrients and the risk of symptomatic kidney stones.". The New England journal of medicine 328 (12): 833–8. ISSN 0028-4793. PMID 8441427.
  9. ^ Bihl G, Meyers A. (August 2001). "Recurrent renal stone disease-advances in pathogenesis and clinical management". Lancet 358 (9282): 651–656. doi:10.1016/S0140-6736(01)05782-8. PMID 11530173.
  10. ^ Hall WD, Pettinger M, Oberman A, et al. (July 2001). "Risk factors for kidney stones in older women in the Southern United States". Am J Med Sci 322 (1): 12–18. doi:10.1097/00000441-200107000-00003. PMID 11465241.
  11. ^ "Sources of vitamin D in orange juice". http://findarticles.com/p/articles/mi_m0FDE/is_3_23/ai_n6138556.
  12. ^ Abelow BJ, Holford TR, and Insogna KL. "Cross-cultural association between dietary animal protein and hip fracture: a hypothesis." Calcif. Tissue Int. 50 (1992): 14-18
  13. ^ Margen S, Chu J-Y, Kaufmann NA, et al. "Urinary calcium and calcium balance in young men as affected by level of protein and phosphorus intake." Journal of Nutrition. 111 (1981): 553-62
  14. ^ Kerstetter JE and Allen LH. "Dietary protein increases urinary calcium." Journal of Nutrition 120 (1990): 134-6
  15. ^ American Journal of Clinical Nutrition 2002;76(1): 245-252
  16. ^ Anne Schaafsma, Gerard M Beelen (1999). "Eggshell powder, a comparable or better source of calcium than purified calcium carbonate: piglet studies" (abstract). Journal of the Science of Food and Agriculture 79 (12): 1596–1600. doi:10.1002/(SICI)1097-0010(199909)79:12<1596::AID-JSFA406>3.0.CO;2-A. http://www3.interscience.wiley.com/cgi-bin/abstract/63003036/ABSTRACT.
  17. ^ Schaafsma A, van Doormaal JJ, Muskiet FA, Hofstede GJ, Pakan I, van der Veer E (March 2002). "Positive effects of a chicken eggshell powder-enriched vitamin-mineral supplement on femoral neck bone mineral density in healthy late post-menopausal Dutch women". Br. J. Nutr. 87 (3): 267–75. doi:10.1079/BJNBJN2001515. PMID 12064336.
  18. ^ Rovenský J, Stancíková M, Masaryk P, Svík K, Istok R (2003). "Eggshell calcium in the prevention and treatment of osteoporosis". Int J Clin Pharmacol Res 23 (2-3): 83–92. PMID 15018022.
  19. ^ "Original Wild Foods vs. Available Foods Today for Instinctos". http://www.beyondveg.com/nieft-k/instincto-guide/instincto-guide1e.shtml.
  20. ^ "USDA National Nutrient Database". http://www.nal.usda.gov/fnic/foodcomp/search.
  21. ^ Combs, G (2008). The Vitamins. Academic Press. p. 161.
  22. ^ a b Weaver, CM (2006). "Calcium". Present Knowledge in Nutrition, 9th Ed.. I. ILSI Press. p. 377.
  23. ^ Remington, Joseph (2005). Remington: The Science and Practice of Pharmacy. Lippincott Williams & Wilkins. pp. 1338. ISBN 0781746736.
  24. ^ Zhao, Y. et al.. "Calcium bioavailability of calcium carbonate fortified soy milk is equivalent to cow's milk in young women". J. Nutr. 135 (10): 2379.
  25. ^ Ligia Martini and Richard J Wood (2002). "Relative bioavailability of calcium-rich dietary sources in the elderly". American Journal of Clinical Nutrition 76 (6): 1345–1350. http://www.ajcn.org/cgi/content/abstract/76/6/1345.
  26. ^ a b Straub, D. A. (2007). "Calcium Supplementation in Clinical Practice: A Review of Forms, Doses, and Indications". Nutrition in Clinical Practice 22: 286. doi:10.1177/0115426507022003286.
  27. ^ Martin, Berdine R. (2002). "Calcium Absorption from Three Salts and CaSO4-Fortified Bread in Premenopausal Women". Journal of Agricultural and Food Chemistry 50: 3874. doi:10.1021/jf020065g.
  28. ^ Weaver, Connie M. (2002). "Absorption of Calcium Fumarate Salts Is Equivalent to Other Calcium Salts When Measured in the Rat Model". Journal of Agricultural and Food Chemistry 50: 4974. doi:10.1021/jf0200422.
  29. ^ Anne Harding. "Calcium May Help With Weight Loss". http://www.rxalternativemedicine.com/headlines_news.php#headline77. Retrieved 2007-07-10.
  30. ^ Dawson-Hughes B, Harris SS, Krall EA, Dallal GE (1997). "Effect of calcium and vitamin D supplementation on bone density in men and women 65 years of age or older". N. Engl. J. Med. 337 (10): 670–6. doi:10.1056/NEJM199709043371003. PMID 9278463.
  31. ^ a b Weingarten MA, Zalmanovici A, Yaphe J (2005). "Dietary calcium supplementation for preventing colorectal cancer, adenomatous polyps and calcium metabolisism disorder.". Cochrane database of systematic reviews (Online) (3): CD003548. doi:10.1002/14651858.CD003548.pub3. PMID 16034903.
  32. ^ Jackson RD, LaCroix AZ, Gass M, et al. (2006). "Calcium plus vitamin D supplementation and the risk of fractures". N. Engl. J. Med. 354 (7): 669–83. doi:10.1056/NEJMoa055218. PMID 16481635.
  33. ^ Grant AM, Avenell A, Campbell MK, et al. (2005). "Oral vitamin D3 and calcium for secondary prevention of low-trauma fractures in elderly people (Randomised Evaluation of Calcium Or vitamin D, RECORD): a randomised placebo-controlled trial". Lancet 365 (9471): 1621–8. doi:10.1016/S0140-6736(05)63013-9. PMID 15885294.
  34. ^ Porthouse J, Cockayne S, King C, et al. (2005). "Randomised controlled trial of calcium and supplementation with cholecalciferol (vitamin D3) for prevention of fractures in primary care". BMJ 330 (7498): 1003. doi:10.1136/bmj.330.7498.1003. PMID 15860827.
  35. ^ Prince RL, Devine A, Dhaliwal SS, Dick IM (2006). "Effects of calcium supplementation on clinical fracture and bone structure: results of a 5-year, double-blind, placebo-controlled trial in elderly women". Arch. Intern. Med. 166 (8): 869–75. doi:10.1001/archinte.166.8.869. PMID 16636212.
  36. ^ Fletcher RH (2006). "Calcium plus vitamin D did not prevent hip fracture or colorectal cancer in postmenopausal women" (subscription required). ACP J. Club 145 (1): 4–5. PMID 16813354. http://www.acpjc.org/Content/145/1/issue/ACPJC-2006-145-1-004.htm.
  37. ^ Baron JA, Beach M, Mandel JS, et al. (1999). "Calcium supplements for the prevention of colorectal adenomas. Calcium Polyp Prevention Study Group". N. Engl. J. Med. 340 (2): 101–7. doi:10.1056/NEJM199901143400204. PMID 9887161.
  38. ^ Bonithon-Kopp C, Kronborg O, Giacosa A, Räth U, Faivre J (2000). "Calcium and fibre supplementation in prevention of colorectal adenoma recurrence: a randomised intervention trial. European Cancer Prevention Organisation Study Group". Lancet 356 (9238): 1300–6. doi:10.1016/S0140-6736(00)02813-0. PMID 11073017.
  39. ^ Lappe, Jm; Travers-Gustafson, D; Davies, Km; Recker, Rr; Heaney, Rp (Jun 2007). "Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial." (Free full text). The American journal of clinical nutrition 85 (6): 1586–91. ISSN 0002-9165. PMID 17556697. http://www.ajcn.org/cgi/pmidlookup?view=long&pmid=17556697.
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References

External links

Wikimedia Commons has media related to: Calcium
Look up calcium in Wiktionary, the free dictionary.
Periodic table
H He
Li Be B C N O F Ne
Na Mg Al Si P S Cl Ar
K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe
Cs Ba La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn
Fr Ra Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr Rf Db Sg Bh Hs Mt Ds Rg Uub Uut Uuq Uup Uuh Uus Uuo
Alkali metals Alkaline earth metals Lanthanoids Actinoids Transition metals Other metals Metalloids Other nonmetals Halogens Noble gases
Calcium compounds
CaB6 · CaBr2 · CaC2 · CaCN2 · CaCO3 · CaC2O4 · CaCl · CaCl2 · Ca(ClO)2 · Ca(ClO3)2 · CaCrO4 · CaF2 · CaH2 · Ca(HCO3)2 · CaH2S2O6 · CaI2 · Ca(IO3)2 · Ca(MnO4)2 · Ca(NO3)2 · CaO · CaO2 · Ca(OH)2 · CaS · CaSO3 · CaSO4 · CaSi2 · CaTiO3 · Ca2P2O7 · Ca2SiO4 · Ca3(AsO4)2 · Ca3(BO3)2 · Ca3(C6H5O7)2 · Ca3N2 · Ca3P2 · Ca3(PO4)2

Categories: Alkaline earth metals | Calcium | Chemical elements | Dietary minerals | Dietary supplements

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