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| {{Chembox new
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| | ImageFileL1 = Cholecalciferol.svg
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| | ImageSizeL1 = 150px
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| | ImageFileR1 = Cholecalciferol-3d.png
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| | ImageSizeR1 = 130px
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| | IUPACName = (3β,5''Z'',7''E'')-9,10-secocholesta-<br>5,7,10(19)-trien-3-ol
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| | OtherNames = vitamin D<sub>3</sub>, activated 7-dehydrocholesterol.
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| | Section1 = {{Chembox Identifiers
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| | CASNo = 67-97-0
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| | EINECS = 200-673-2
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| | PubChem =
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| | SMILES = CC(C)CCC[C@@H](C)[C@H]<br>1CCC2C(\CCCC12C)=C\<br>C=C3\C[C@@H](O)CCC3=C
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| | MeSHName =
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| | Section2 = {{Chembox Properties
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| | Formula = C<sub>27</sub>H<sub>44</sub>O
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| | MolarMass = 384.64 g/mol
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| | Appearance = White, needle-like crystals
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| | Density =
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| | MeltingPt = 83–86 °C
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| | BoilingPt =
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| | Section3 = {{Chembox Hazards
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| | Solubility = Practically insoluble in water, freely soluble in Abs. Ethanol, Methanol and some other organic solvents. Slightly soluble in vegetable oils.
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| | MainHazards =
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| | FlashPt =
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| | Autoignition =
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| {{SI}}
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| ==Overview==
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| '''Cholecalciferol''' is a form of [[Vitamin D]], also called '''vitamin D<sub>3</sub>'''.
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| It is structurally similar to [[steroid]]s such as [[testosterone]], [[cholesterol]], and [[cortisol]] (though vitamin D<sub>3</sub> itself is a [[secosteroid]]).
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| 1g of pure vitamin D<sub>3</sub> is 40 000 000 (40x10<sup>6</sup>) [[International unit|IU]], or in other words, one IU is 0.025 μg.
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| ==Forms==
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| Cholecalciferol has several forms:
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| * Calciol <ref>[http://www.online-medical-dictionary.org/Calciol.asp?q=Calciol online medical dictionary]</ref>, is an inactive, un[[hydroxylated]] form of vitamin D<sub>3</sub>)
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| * [[calcidiol]] (also called 25-hydroxyvitamin D<sub>3</sub>), is the blood calcium form
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| * [[calcitriol]] (also called 1,25-dihydroxyvitamin D<sub>3</sub>), is the active form of D3.
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| ==Metabolism==
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| [[7-Dehydrocholesterol]] is the precursor of vitamin D<sub>3</sub> and only forms the vitamin after being exposed to [[UV radiation]]. This creates calciol.
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| After exposure to the sun, calciol is sent to the [[liver]] to be [[hydroxylated]] where it becomes [[Calcidiol]].
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| Next, it is sent to the [[kidney]] and once again hydroxylated becoming [[Calcitriol]]. Calcitriol is the active hormone form of vitamin D<sub>3</sub>, for this reason vitamin D is often referred to as a [[prohormone]].
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| ==As food fortification==
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| Cholecalciferol is the form of vitamin D normally added during fortification of foods. Cholecalciferol is produced industrially by the irradiation of [[7-dehydrocholesterol]] extracted from [[lanolin]] found in sheep's wool. In products where animal products are not desired, the alternative is to use [[ergocalciferol]] (also known as vitamin D<sub>2</sub>) derived from the fungal sterol [[ergosterol]].
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| ===Dose===
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| While the absorption of cholecalciferol and ergocalciferol is approximately equivalent in healthy individuals, vitamin D3 is three to ten <ref name=armas> {{cite journal |author=Armas L, Hollis B, Heaney R |title=Vitamin D2 is much less effective than vitamin D3 in humans |journal=J Clin Endocrinol Metab |volume=89 |issue=11 |pages=5387–91 |year=2004 |pmid=15531486}} [http://jcem.endojournals.org/cgi/content/full/jcem;89/11/5387 Free full text]</ref> times more potent than vitamin D2, and has more prolonged effects. However, the human body cannot tolerate intake of as much vitamin D3 per day compared to the body's upper-limit intake of vitamin D2<ref name=armas/>, limiting the overall efficacy of taking vitamin D3 supplements as opposed to vitamin D2 supplements despite vitamin D3's higher potency. The current standard is to recommend equivalent doses of vitamin D2 as vitamin D3<ref name=armas/>, but with regard to the mentioned mechanisms it has been suggested<ref name=armas/> that instead, the [[Recommended Daily Allowance]]s (RDA) or [[International Unit]]s (IU) of vitamin D2 and D3 should be changed to recommend approximately 10 times more daily intake for vitamin D2 than vitamin D3.
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| For a current and illustrated discussion on this topic see:
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| Tavera-Mendoz, Luz E. & White, John H. (2007, November). Cell Defenses and the Sunshine Vitamin. [[Scientific American]], pp.62-72.
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| ==Stability==
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| Cholecalciferol is very sensitive to [[ultraviolet|UV radiation]] and will rapidly, but reversibly break down to form supra-sterols, which can further irreversibly convert to tachysterol.
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| ==See also==
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| * [[Hypervitaminosis D]], Vitamin D poisoning
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| * [[Ergocalciferol]], vitamin D2.
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| * [[25-Hydroxyvitamin D3 1-alpha-Hydroxylase]], calcidiol converted in kidneys to calcitriol by this [[enzyme]].
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| ==References==
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| {{Reflist}}
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| {{vitamin}}
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| {{Sterols}}
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| [[Category:Secosteroids]]
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| [[fr:Cholécalciférol]]
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| [[ro:Colecalciferol]]
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| {{WH}}
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| {{WS}}
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