Vitamin D metabolism

Vitamin D is synthesized via a series of orchestrated steps. First, ultraviolet light converts 7-dehydrocholesterol to previtamin D3, which is then converted to vitamin D3 .

Relatively minimal sun exposure is needed to synthesize cholecalciferol in the skin; 10-15 minutes of exposure provides more vitamin D3 than any known dietary source.
However, sedentary indoor lifestyles and concerns regarding skin cancer have led to a dramatic increase in vitamin D deficiency, even in warmer climates.



In the absence of sun exposure, cholecalciferol can also be obtained naturally from the diet , from foods that are fortified with vitamin D, or from vitamin D supplements.
Vitamin D2 is an alternative vitamin D supplement derived from plants that is less biologically potent than vitamin D3.

Vitamin D binding protein carries vitamin D2 and D3 to the liver, which converts them to 25-hydroxy vitamin D , the major circulating form of vitamin D that is measured by routine laboratory testing.

External links:

Medicalnewstoday:Vitamin D metabolism
Sciencedaily:Vitamin D metabolism