Vitamin D update – 3 is better than 2

model of biologically active vitamin D3

Ever look at the ingredients list for your supplement or fortified food?  You likely see a bewildering list of chemical names for vitamins and minerals, including a listing for one of the two forms of vitamin D: ergocalciferol (vitamin D2) or cholecalciferol (vitamin D3).  Both can be metabolized in the body to the biologically active forms, but vitamin D experts have suspected that D3 is more potent and useful than D2.  D3 is the form made by human skin cells, when the right rays of sunlight shine on skin that’s not covered with sunscreen.  D2 is not made by humans.  It’s produced by plants and fungi in response to UV light.  For example, mushrooms are known to make D2 when exposed to sunlight.

New research by noted vitamin D expert Dr. Robert Heaney MD compared the absorption of these two forms.  Subjects were given large doses – 50,000 i.u. per week for 12 weeks.  Vitamin D3 was 56-87% more effective at raising blood levels and storage levels in fat cells.  He notes that unfortunately, most of the prescription vitamin D is the D2 form.  Meaning prescription doses might not be so well absorbed.  More than 4 years ago, a review of vitamin D in the American Journal of Clinical Nutrition concluded that vitamin D2 should not be used in prescriptions:

Vitamin D2, or ergocalciferol, should not be regarded as a nutrient suitable for supplementation or fortification.

But it is still used, and you can find plenty of food products fortified with D2 on grocery store shelves.  Look for “ergocalciferol” on the ingredients list.  For example, the Almond Breeze “milk” alternative I discussed yesterday is fortified with vitamin D2.  By contrast, lately many supplement companies are putting big “with D3” labels on their packaging, capitalizing on the trend in vitamin D thinking.  If you take vitamin D, be sure your supplement is made with D3, and check food product packages for the type of vitamin D used in fortification.  No sense buying a fortified product if the form of vitamin in question is less potent.

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