How does the quality of vitamin D2 compare with D3?

by Thomas
( Maine)

There has been a great deal of controversy regarding the quality of D2 compared with D3. Doctor Michael Holick, Professor of Medicine, Physiology and Biophysics at the BU Medical Center and author of The Vitamin D Solution: A 3-Step Strategy to Cure Our Most Common Health Problem has been referred to by Dr. Mark Hyman as the world's leading authority on Vitamin D. Dr. Holick has recently researched this question of the quality of D2 and concluded on page 41 "I demonstrated that D2 is just as effective as D3 and put to rest this long standing myth" ( i.e.that D2 is less effective than D3).

He lists the Vitamin D content of various food and I noticed that the highest concentration of vitamin D -by far- is sun dried Shitake mushrooms with 1600 IU's in just 3.5 ounces.This is much higher, ounce for ounce, than even cod liver oil or wild salmon. Of course the best source of Vitamin D is from the sun- under the right conditions, which he outlines in his book.

So the question is: Do you know of any recent research findings which would contradict Holick's conclusions. Thanks so much for your thoughts!

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Not Contradict, but...
by: Kerri Knox, RN- The Immune Queen!

Hi Thomas,

I believe that Dr. Holick's study that you are referring to actually only tested the rise in Vitamin D blood levels in comparison to D2 and D3 (but please send me the study if that is incorrect).

So, Dr. Holick found in his study that the two raise blood levels equally- but that does not mean that they are equal. Other studies, not more recent but no less valid, have shown that Vitamin D2 doesn't activate genes as well as D3 and that the half life of D2 is less and that it is more toxic.

Dr. Reinholdt Vieth, while maybe not the world's premier Vitamin D researcher, certainly has done some impressive research on vitamin d and has outlined his reasoning for choosing D3 over D2 in the metanalysis The Case Against Ergocalciferol.

Another telling thing for me is that almost no humans get Vitamin D2 in any form on a natural basis. While SUN-DRIED shitake mushrooms (not 'just' shitake mushrooms) have the highest amount of Vitamin d (in the form of D2), almost no native cultures in the world eat vitamin d2 rich sun-dried shitake mushrooms as a staple food. This in comparison to cultures who have eaten copious amounts of Vitamin D3 rich fish, butter, eggs and lard on a regular basis to get their Vitamin D (in the form of Vitamin D3)- and of course the all pervasive sun gets us vitamin d3 and not D2.

So, the analogy that I use when people claim that Dr. Holick's work on raising blood levels ends the discussion about D2 vs D3, I ask them what car they drive....

ANY car will get you from point A to point B, but most people drive a car for more than simply getting from Point A to Point B, right?? So, personally I want my vitamin d to have a longer half life, be less toxic and get me the disease prevention that is so promising in all of the research on this nutrient.

Will Vitamin D2 do that as effectively as D3?? Preliminary research that has been done on D3's activation of the VDR suggests that they are NOT the same and that D2 and D3 may NOT have the same disease fighting potential. Can I be sure of that? Nope. But I can be sure that my ancestors got almost no D2 and got copious amounts of D3 from the sun and from the few Vitamin D containing foods that are out there.

So, personally, I'm going to continue taking D3 since that is the form that is 'bioidentical' with human physiology. If I were a plant, I would want D2 since that is what is bioidentical for plants...

Kerri Knox RN Immune Health Queen

Kerri Knox, RN- The Immune System Queen
Functional Medicine Practitioner
Immune System

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