Vitamin D3 Performs Slightly Better Than D2 in Clinical Trial

I have updated the article, Calcium and Vitamin D, with a synopsis of the following clinical trial:

“A 2013 study from Germany found that with supplementing daily for 8 weeks at about 2,000 IU, D3 was more effective at raising vitamin D levels (1). The average 25(OH)D levels increased 46 nmol/l in the D3 group (for an average of 89 nmol/l) but only 30 nmol/l in the D2 group (for an average of 68 nmol/l). Vitamin D2 supplementation appeared to decrease the amount of circulating vitamin D3. PTH levels were not different between groups. Because D2 raised levels into the recommended range (50 – 125 nmol/l), it seems preliminary to assume that D3 is more healthy based on these results, though evidence is mounting that D3, even at smaller doses, can raise vitamin D levels higher or more quickly than D2.”

I don’t think this has any health implications for most vegans. If you have experienced a stubborn vitamin D deficiency, it adds some credence to the idea that you should try vitamin D3. Vegan vitamin D3 is available.


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1. Lehmann U, Hirche F, Stangl GI, Hinz K, Westphal S, Dierkes J. Bioavailability of vitamin D(2) and D(3) in healthy volunteers, a randomized placebo-controlled trial. J Clin Endocrinol Metab. 2013 Nov;98(11):4339-45. doi: 10.1210/jc.2012-4287. Epub 2013 Sep 3. | link

3 Responses to “Vitamin D3 Performs Slightly Better Than D2 in Clinical Trial”

  1. Gary Safron Says:

    i used to have low vit D2 levels when I got tested at my doctors office.
    Then I went to Quest Diagnostics and had the LC/MS/MS test (the most accurate for vit. D2)and their was about a 40% increase in my vitamin D2 levels and above normal 1 month later. I personally think vit D2 is just as good as D3 it’s just getting the right test.

  2. theveganscientist Says:

    The D2 vs D3 debate has been going on for some time now. I read a review circa 2010 that summarized the findings to date. The highlights were:

    1) The efficacy ratio of D2:D3 varies between 1:1 and 1:10 with 1:4 being the average of the studies done at time of publication (this recent study shows a 1:1.5 efficacy ratio)

    2). At very low circulating levels of 25(OH)D (<10ng/mL, 25mmol/L) D2 is equally effective in raising 25(OH)D, but at higher basal levels the efficacy ratio drops.

    3). The basal level, the dosage, duration of study, and route of administration seem to affect the outcome (the later might be due to the dosage in Bolus injections is usually higher in the studies).

    Some papers note 25(OH)D2 has a shorter elimination 1/2 life (50,000IU bolus injection) which the authors suggest might be the reason for the reduced efficacy, but this paper indicates another mechism: the reduction of endogenous 25(OH)D3 production from D2 administration.

    It may be that ergocalciferol might "hyperactivate" the feedback system that shuts down Endogenous D3 production when a person sits out in the sun producing enough 25(OH)D3.

    Another interesting thing that falls out of these studies is that people who have low 25(OH)D (<10ng/mL) It takes about 5000IU of Vit D2/day to get their levels up to ~40-50ng/mL. Extrapolating the dosage in this study is also consistent with this number.

    I'm not convinced D2 is inferior overall since Calcitriol is the active hormone and calcitriol made from D3 is a different molecule (slightly) than calcitriol from D2. I've not seen the potency of calcitriol vitamers quantitated. If D2-Calcitriol is 1.5x the potency of D3-calcitriol, then Vit D2 is equivalent is Vit D3 if the D2-calcidiol is 1.5x lower in the blood. We just measure Calcidiol because it's easier than measuring Calcitriol.

    In the winter months, I take 5000IU, Vegan D3 3x/week. In the summer, I take 2000IU D2 3x/week.

    My levels have been between 40-50ng/mL for 6 years now. Before supplementation, my test result was 8ng/mL (brown skin, February in Chicago). 2000IU/day of D2 back then got my 25(OH)D to 29ng/mL in 6 weeks

  3. theveganscientist Says:

    Btw Gary, the study cited above measured the 25(OH)D vitamers with LC-MS-MS.

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