Vitamin D3

http://www.ajcn.org/cgi/content/full/84/4/694

Vitamin D₂, if given in high enough doses, prevents infantile rickets and is capable of healing adult osteomalacia. However, the inefficiency of vitamin D₂ compared with vitamin D₃, on a per mole basis, at increasing 25(OH)D is now well documented, and no successful clinical trials to date have shown that vitamin D₂ prevents fractures (19-21, 47). Given the assumption that the intake of any nutrient will deliver defined effects [ie, supplementation with vitamin D will lead to an increase in 25(OH)D or fracture prevention], it is clear that vitamin D₂ does not fit this current nutritional notion. This is not to suggest that vitamin D₂ is not efficacious, but, because the units of the 2 forms is clearly not equivalent, likely due to its distinct metabolic features and diminished binding of vitamin D₂ metabolites to DBP in plasma, continual application of vitamin D₂ in clinical use, including in research trials, only serves to confound our understanding of optimal vitamin D dosing recommendations. Furthermore, the public expects to derive the equivalent effect per unit dose of vitamin D, whether it is vitamin D₂ or vitamin D₃. The scientific community is aware that these molecules are not equivalent. Therefore, vitamin D₂ should no longer be regarded as a nutrient appropriate for supplementation or fortification of foods.