Ergocalciferol/ja: Difference between revisions

'''Ergocalciferol''', also known as '''vitamin D₂''' and nonspecifically '''calciferol''', is a type of [[vitamin D]] found in food and used as a [[dietary supplement]]. As a supplement it is used to prevent and treat [[vitamin D deficiency]]. This includes vitamin D deficiency due to [[malabsorption|poor absorption by the intestines]] or [[liver disease]]. It may also be used for [[hypocalcemia|low blood calcium]] due to [[hypoparathyroidism]]. It is used by mouth or [[intramuscular|injection into a muscle]].

Excessive doses can result in increased urine production, [[high blood pressure]], [[kidney stones]], [[kidney failure]], weakness, and constipation. If high doses are taken for a long period of time, [[tissue calcification]] may occur. Normal doses are safe in [[pregnancy]]. It works by increasing the amount of [[calcium]] absorbed by the intestines and kidneys. Food in which it is found include some [[mushrooms]].

Ergocalciferol was first described in 1936. Ergocalciferol is available as a [[generic medication]] and [[over the counter]]. Certain foods such as [[breakfast cereal]] and [[margarine]] have ergocalciferol added to them in some countries.

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==Use==

[[File:Vitamin D pills.jpg|thumb|Vitamin D₂ supplements]]

Ergocalciferol may be used as a vitamin D [[dietary supplement|supplement]], whereas [[cholecalciferol]] (vitamin D₃) is produced naturally by the skin when exposed to ultraviolet light. Ergocalciferol (D₂) and cholecalciferol (D₃) are considered to be equivalent for vitamin D production, as both forms appear to have similar efficacy in ameliorating [[rickets]]  Conflicting reports exist, however, concerning the relative effectiveness, with some studies suggesting that ergocalciferol has less efficacy based on limitations in absorption, binding, and inactivation. A [[meta-analysis]] concluded that evidence usually favors cholecalciferol in raising vitamin D levels in blood, although it stated more research is needed.

==Mechanism==

Ergocalciferol is a [[secosteroid]] formed by a [[photochemistry|photochemical]] bond breaking of a [[steroid]], specifically, by the action of [[ultraviolet light]] (UV-B or UV-C) on [[ergosterol]], a form of provitamin D₂.

Like [[cholecalciferol]], ergocalciferol is inactive by itself. It requires two [[hydroxylation]]s to become active: the first in the liver by [[CYP2R1]] to form 25-hydroxyergocalciferol (ercalcidiol or 25-OH D₂), and the second in the kidney by [[CYP27B1]], to form the active 1,25-dihydroxyergocalciferol (ercalcitriol or 1,25-(OH)₂D₂), which activates the [[vitamin D receptor]]. Unlike [[cholecalciferol]], 25-hydroxylation is not performed by [[CYP27A1]] for ergocalciferol.

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Ergocalciferol and metabolites have lower affinity to the [[vitamin D-binding protein]] compared to the D₃ counterparts. The binding affinity of ercalcitriol to the vitamin D receptor is similar to that of [[calcitriol]]. Ergocalciferol itself and metabolites can be deactivated by 24-hydroxylation.

==Sources==

'''Fungus''', from USDA nutrient database (per 100g), D₂ + D₃:

* [[Agaricus bisporus|Mushrooms, ''Agaricus bisporus'']]:

** raw portobello: 0.3&nbsp;μg (10 IU); exposed to ultraviolet light: 11.2&nbsp;µg (446 IU)

** raw crimini: 0.1&nbsp;μg (3 IU); exposed to ultraviolet light: 31.9&nbsp;µg (1276 IU)

* [[Shiitake|Mushrooms, shiitake]]:

** raw: Vitamin D (D₂ + D₃): 0.4 μg (18 IU)

** dried: Vitamin D (D₂ + D₃): 3.9&nbsp;μg (154 IU)

'''Lichen'''

* ''[[Cladina]] arbuscula'' specimens grown under different natural conditions contain provitamin D₂ and vitamin D₂, ranges 89-146 and 0.22-0.55&nbsp;μg/g dry matter respectively. They also contain vitamin D₃ (range 0.67 to 2.04&nbsp;μg/g) although provitamin D₃ could not be detected. Vitamin D levels correlate positively with UV irradiation.

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'''Plantae'''

* [[Alfalfa]] (''Medicago sativa'' subsp. sativa), shoot: 4.8&nbsp;μg (192 IU) vitamin D₂, 0.1&nbsp;μg (4 IU) vitamin D₃

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=== Biosynthesis ===

The vitamin D₂ content in mushrooms and ''C. arbuscula'' increase with exposure to ultraviolet light. [[Ergosterol]] (provitamin D₂) found in these fungi is converted to previtamin D₂ on UV exposure, which then turns into vitamin D₂. As cultured mushrooms are generally grown in darkness, less vitamin D₂ is found compared to those grown in the wild or dried in the sun.

When fresh mushrooms or dried powders are purposely exposed to ultraviolet light, vitamin D₂ levels can be concentrated to much higher levels. The irradiation procedure does not cause significant discoloration, or whitening, of mushrooms. Claims have been made that a normal serving (approx. 2 oz or 60 grams) of fresh mushrooms treated with ultraviolet light have increased vitamin D content to levels up to 80 micrograms or 3200 IU if exposed to just five minutes of UV light after being harvested.

Button mushrooms with enhanced vitamin D₂ content produced this way functions similarly to a vitamin D₂ supplement; both effectively improves vitamin D status. Vitamin D₂ from UV-irradiated yeast baked into bread or mushrooms is bioavailable and increases blood levels of 25(OH)D.

==Names==

Viosterol, the name given to early preparations of irradiated ergosterol, is essentially synonymous with ergocalciferol. However, currently, Viosterol is also the brand name for [[cholecalciferol]] (vitamin D₃) in some countries.

Ergocalciferol is manufactured and marketed under various names, including Deltalin ([[Eli Lilly and Company]]), Drisdol (Sanofi-Synthelabo), and Calcidol (Patrin Pharma).

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== External links ==

{{Vitamins}}

{{Sterols}}

{{Vitamin D receptor modulators}}

{{Cholesterol metabolism intermediates}}