vitamin D supplements after gastric bypass

Question
I am an RD with a weight loss surgery program.  Most of my research on vitamin D indicates that D3 is the best supplement to use with vitamin D deficiency, however, the ASMBS recommends D2 to resolve cases of severe deficiency (<30ng/ml).  I cannot figure out why this is the case?  Is it simply that D2 is the prescription form for high doses.  Will D3 work as well or not as well?  Thank you.

Answer
Hi Jennifer,

This is a great question - I am surprised that more people don't ask it.  There are some rather old guidelines used in some discrete corners of nutrition manufacture in the US.  Though it is not written as law anywhere, traditionally, there have been some levels and forms of nutrients that are only Rx and some that are only dietary supplements.  For example, many vitamin manufacturers believe that they can only make potassium in 99mg increments - but this is really just tradition and not a regulation.  With Vitamin D you have several issues that sort of go as follows:

1) The only form of vitamin D approved as a drug by the FDA is D2 - no one with a D3 product has ever gone through the drug approval process.  So as far as Rx is concerned in the US, that's what you get.  In the rest of the world, you can get Rx D3.

2) Vitamin manufacturers believe that they can't manufacture very-high potency vitamin D3 products.  So usually, you see vitamin products cap out at 5000 IU.  In fact, we actually had to negotiate heavily with our manufacturing facility a few years back to get this made.  Now several companies are doing it.  But most won't go above the UL set by the IOM which is 2000 IU.  

3) The law is not clear.  I think it would be legal for a vitamin manufacturer to market a 50,000 IU product, but I don't know if anyone will risk it because the law is just not perfectly clear.  Even if it's not explicitly written, someone could argue that a "vitamin" at this level is really a drug.  They might be right.  

As far a human physiology goes, vitamin D3 is definitely better.  While we don't yet have activity equivalents as we do with folate of vitamin A, we will - most studies looking at this show that D3 has 2-3 times the activity of D2 with lower potential for toxicity.  

I hope this is helpful!

In Health,

Dr. Jacques

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