agate
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 Posted: Fri Sep 06, 2013 6:20 pm Post subject: Vitamin D3 may beat D2 as supplement |
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For years I've been hearing that if you're taking a vitamin D supplement, you should make sure you're getting D3 and not D2. This article indicates that there is evidence for this advice.
From MedPage Today, September 5, 2013:
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Vitamin D3 May Beat D2 as Supplement
By Kristina Fiore, Staff Writer, MedPage Today
Reviewed by F. Perry Wilson, MD, MSCE; Instructor of Medicine, Perelman School of Medicine at the University of Pennsylvania and Dorothy Caputo, MA, BSN, RN, Nurse Planner
In a randomized controlled trial, increases in serum 25(OH)D over 8 weeks were significantly greater among patients on vitamin D3 than those taking D2 or placebo (89.2 nmol/L versus 67.8 nmol/L and 32.1 nmol/L, P<0.01), Jutta Dierkes, PhD, of the University of Bergen in Norway, and colleagues reported online in the Journal of Clinical Endocrinology and Metabolism.
And giving vitamin D2 appeared to diminish vitamin D3 levels, they found.
"Our major finding is that vitamin D3 increased 25(OH)D more effectively than vitamin D2," they wrote. "By measuring the specific hydroxylated forms, we have been able to show that the underlying reason for this difference is a substantial decrease in 25(OH)D3 in subjects receiving vitamin D2."
It has long been debated whether the two supplement forms of vitamin D are bioequivalent. Some studies have suggested that vitamin D2 -- ergocalciferol, the type commonly found in plants, mainly mushrooms -- is less biologically active than vitamin D3, or cholecalciferol, which is found in animals and produced in human skin.
Dierkes and colleagues argued that it's important to know which form is more effective, given the widespread problem of vitamin D deficiency. So they conducted a parallel-group, randomized controlled trial that tested the efficacy of supplementation with 50 mcg (2,000 IU) per day of one form or the other of the vitamin, or placebo, over 8 weeks.
They conducted the study during the winter at a high latitude, when UVB radiation is virtually absent, they noted.
At baseline, the average total 25(OH)D concentration was 40.2 nmol/L, "indicating a high degree of suboptimal vitamin D status in these healthy, young volunteers, with no significant differences between groups."
Over the 8 weeks of the study, total levels of 25(OH)D rose significantly for those in both of the supplementation groups, but fell among those on placebo -- but levels differed significantly between all three groups, with greater increases for those taking vitamin D3 supplements (P<0.01).
Vitamin D2 levels were below the limit of quantification in almost all patients at baseline, and only rose to detectable levels for those supplemented with D2.
For those taking D3 supplements, 25(OH)D3 levels rose significantly over the study (41.5 nmol/L to 88 nmol/L over 8 weeks, P<0.01) -- but 25(OH)D3 levels fell off significantly among those taking vitamin D2 (from 36.4 nmol/L to 16.6 nmol/L, P<0.01) or placebo (39.4 nmol/L to 31.1 nmol/L, P<0.01).
The more pronounced decrease in vitamin D3 in the vitamin D2 group was "the most interesting result of our study," the researchers wrote. Other studies have shown similar results but have not discussed these findings in depth, so the biological mechanism "remains to be elucidated," they said.
The study was limited because it did not measure the active forms of vitamin D, including 1,25(OH)2D2 and 1,25(OH)2D3.
Still, they concluded that the findings "question the usefulness of vitamin D2 supplements," and suggested that instead, vitamin D3 "should be used for supplementation and fortification purposes."
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The study was supported by the German Ministry of Education and Research.
The researchers reported no conflicts of interest.
Primary source: Journal of Clinical Endocrinology & Metabolism
Source reference: Lehmann U, et al "Bioavailability of vitamin D2 and D3 in healthy volunteers, a randomized placebo-controlled trial" J Clinical Endocrinol Metab 2013; DOI: 10.1210/jc.2012-4287. |
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