Description

Vitamin D comes from two sources: endogenous, which is produced in the skin on exposure to sunlight, and exogenous, which is ingested in foods and supplements. The chemical structures of the types of vitamin D are slightly different, and they are named vitamin D₂ (ergocalciferol, which comes from plants) and vitamin D₃ (cholecalciferol, which comes from animals). The D₂ form is found in fortified foods and in most vitamin preparations and supplements. Vitamin D₃ is the form produced in the body and is also used in some supplements. Vitamin D₂ and D₃are equally effective when they are converted by the liver and the kidney into the active form, 1,25-dihydroxyvitamin D.