Step I Vitamin D2 vs D3

[swtiepie711]

On p144 of the Biochemistry Kaplan notes, it was said that milk contains Vitamin D2 derived from irradiated plant ergocalciferol.

However, in First Aid and on most of the websites I can find, it says that milk has Vitamin D3 in it, not D2.

On one hand, I think "who cares?" - on the other hand, it means bypassing a step (i.e. Vitamin D3 must be converted to 23-hydroxycholecalciferol in the liver) - so does anyone know where I can find out which is for sure or if this even matters? TIA.

 

[facetguy]

Milk can contain either D2 or D3. Both need to be hydroxylated in the liver.

Here's a paper on D2 vs. D3: http://www.ajcn.org/cgi/content/full/84/4/694

Regarding effectiveness in raising blood 25-OH-D levels, D3 is almost always considered the more effective form, although a recent paper did dispute this:
http://www.ncbi.nlm.nih.gov/pubmed/...nkpos=3&log$=relatedarticles&logdbfrom=pubmed

Good luck.