Vitamin D2
Also Known As: Vitamin D2, Ergocalciferol, Drisdol, Calcidol
Ergocalciferol is a provitamin form of vitamin D, also called vitamin D2. In isolated manufactured formats, it is marketed under various names including Deltalin (Eli Lilly and Company), Drisdol (Sanofi-Synthelabo), and Calcidol (Patrin Pharma). Ergocalciferol is created when ultraviolet light activates ergosterol.[citation needed]
Conflicting evidence exists for how similarly D2 and D3 behave in the body and whether they are equally active or efficient in production of 25-hydroxyvitamin D (25(OH)D), the active hormone. Some preliminary studies indicate D3 is more potent,[10][11] while others report equal efficacy.[1][12][13] Both forms appear to have similar efficacy in ameliorating rickets[14] and reducing the incidence of falls in elderly patients.[15]
The metabolism of each appears to be different, with the vitamin D binding protein possibly having greater affinity for 25(OH)D3 than for 25(OH)D2, as shown in one study.[10] Cholecalciferol (vitamin D3) is sensitive to UV radiation and rapidly, but reversibly, forms other sterols which can further irreversibly convert to ergosterol.
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