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| Cholecalciferol | |
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| IUPAC name | (3β,5Z,7E)-9,10-secocholesta- 5,7,10(19)-trien-3-ol |
| Other names | vitamin D3, activated 7-dehydrocholesterol. |
| Identifiers | |
| CAS number | 67-97-0 |
| EINECS number | |
| SMILES |
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| Properties | |
| Molecular formula | C27H44O |
| Molar mass | 384.64 g/mol |
| Appearance | White, needle-like crystals |
| Melting point |
83–86 °C |
| Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox references |
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Cholecalciferol is a form of Vitamin D, also called vitamin D3. It is structurally similar to steroids such as testosterone, cholesterol, and cortisol (though vitamin D3 itself is a secosteroid).
1g of pure vitamin D3 is 40 000 000 (40x106) IU, or in other words, one IU is 0.025 μg.
Contents |
Forms
Cholecalciferol has several forms:
- Calciol 1, is an inactive, unhydroxylated form of vitamin D3)
- calcidiol (also called 25-hydroxyvitamin D3), is the form measured in the blood to assess vitamin D status.
- calcitriol (also called 1,25-dihydroxyvitamin D3), is the active form of D3.
Metabolism
7-Dehydrocholesterol is the precursor of vitamin D3 and only forms the vitamin after being exposed to solar UV radiation. This creates calciol.
Calciol is then hydroxylated in the liver to become calcidiol.
Next, calcidiol is once again hydroxylated, this time in the kidney, and becomes calcitriol. Calcitriol is the active hormone form of vitamin D3; for this reason vitamin D is often referred to as a prohormone.
As food fortification
Cholecalciferol is the form of vitamin D normally added during fortification of foods.citation needed 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, one alternative is to use ergocalciferol (also known as vitamin D2) derived from the fungal sterol ergosterol. Another alternative exists in the form of Algas Calcareas, an Algae from South America.
Dose
There are conflicting reports concerning the absorption of cholecalciferol (D3) versus ergocalciferol (D2) with some studies suggesting a difference2, and while initial reports suggested that vitamin D3 and others no difference2 3. Currently D2 and D3 doses are frequently considered interchangeable but more research is needed to clarify this. Cholecalciferol is synthesized in the skin from dehydrocholesterol under the action of ultraviolet B light. It reaches an equilibrium after several minutes depending of several factors including conditions of sunlight (latitude, season, cloud cover, altitude), age of skin, and color of skin. At equilibrium excess cholecalciferol is broken down into benign products which are not found outside the skin. Hepatic synthesis of cholecalcidiol (25-hydroxycholecalciferol) is only loosely regulated, if at all, and blood levels of this molecule largely reflect the amount of vitamin D produced in the skin or ingested. In contrast, the activity of 1-alpha-hydroxylase in the kidney is tightly regulated and serves as the major control point in production of the active circulating hormone calcitriol. Most of the cholecalcidiol is converted to calcitriol in the tissues which is less tightly controlled.
Stability
Cholecalciferol is very sensitive to UV radiation and will rapidly, but reversibly break down to form supra-sterols, which can further irreversibly convert to tachysterol.
Therapeutic Application
A 2008 study published in Cancer Research has shown the addition of vitamin D3 (along with calcium) to the diet of mice fed a regimen nutritionally similar to a new Western diet prevented colon cancer development.4
Alternative Views
There's a minority view, often associated with Trevor Marshall, which asserts that low levels of 25D are often due to overconversion into calcitriol because of chronic infection rather than 25D deficiency. [1]
See also
- Hypervitaminosis D, Vitamin D poisoning
- Ergocalciferol, vitamin D2.
- 25-Hydroxyvitamin D3 1-alpha-Hydroxylase, a kidney enzyme that converts calcidiol to calcitriol.
References
- ^ online medical dictionary
- ^ a b Armas L, Hollis B, Heaney R (2004). "Vitamin D2 is much less effective than vitamin D3 in humans". J Clin Endocrinol Metab 89 (11): 5387–91. doi:. PMID 15531486 Cholecalciferol is synthesized by the bone marrow of the skeletal system., http://jcem.endojournals.org/cgi/content/full/jcem;89/11/5387.
- ^ Hollick, Biancuzzo, Chen, Klein, Young, Bilbud, Reitz, Salameh, Ameri, Tanenbaum (2007). "Vitamin D2 is as effective as vitamin D3 in maintaining circulating concentrations of 25-hydroxyvitamin-D "Context: Two reports suggested that vitamin D2 is less effective than vitamin D3 in maintaining vitamin D status"". J Clin Endocrinol Metab, http://jcem.endojournals.org/cgi/rapidpdf/jc.2007-2308v1.
- ^ Yang, Kurihara, Fan, Newmark, Rigas, Bancroft, Corner, Livote, Lesser, Edelmann, Velcich, Lipkin, Augenlicht (2008). "Dietary Induction of Colonic Tumors in a Mouse Model of Sporadic Colon Cancer "Context: Colonic tumors were prevented by elevating dietary calcium and vitamin D3 to levels comparable with upper levels consumed by humans"". Cancer Research, http://cancerres.aacrjournals.org/cgi/content/short/68/19/7803?rss=1.
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- This page was last modified on 22 November 2008, at 13:45.
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