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Vitamin D3 increased and Vitamin D2 decreased the D3 serum levels – RCT Sept 2013

Bioavailability of Vitamin D2 and D3 in Healthy Volunteers, a randomised placebo-controlled trial

The Journal of Clinical Endocrinology & Metabolism September 3, 2013 jc.2012-4287
Ulrike Lehmann 1,
Frank Hirche 1,
Gabriele I. Stangl 1,
Katja Hinz 2,
Sabine Westphal 2 and
Jutta Dierkes 3
1Institute of Agricultural and Nutritional Sciences, Martin-Luther University Halle-Wittenberg;
2Institute of Clinical Chemistry and Biochemistry, Otto-von-Guericke University Magdeburg;
3Department of Clinical Medicine, University of Bergen, Norway

Address all correspondence and requests for reprints to: Jutta Dierkes PhD, Department of Clinical Medicine, Post Box 7804, N-5020 Bergen, Norway, email: jutta.dierkes at med.uib.no, phone: 004755977344, fax 004755975890.

Background: The bioequivalence of the different forms of vitamin D, ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3) has been questioned. Earlier studies have suggested that vitamin D2 is less biologically active than vitamin D3.

Objective and Design: In a parallel study, we tested the effects of supplementation with 50 μ g/day doses of vitamin D2 or D3 or a placebo over a period of 8 weeks on 25(OH)D2, 25(OH)D3, their sum 25(OH)D (primary outcome variables), and parathyroid hormone in healthy volunteers applying a double blind, randomized study design. The study was conducted during winter 2012 in Halle (Saale), at latitude of 51°47N, when UVB irradiation is virtually absent. Blood samples for the determinations of the vitamin D status and PTH were collected at baseline and then after 4 and 8 weeks of supplementation.

Results: In the placebo group (n=19), 25(OH)D3 decreased from 39.4±14.2 to 31.1±12.4 nmol/L after 8 weeks (p < 0.01).
In the vitamin D3 group (n=42), the concentrations of 25(OH)D3 increased from 41.5±22.8 nmol/L at baseline to 88.0±22.1 nmol/L after 8 weeks (p<0.01).
In the group receiving vitamin D2 (n=46), the 25(OH)D2 concentrations increased significantly, while the 25(OH)D3 concentration fell from 36.4±13.3 nmol/L at baseline to 16.6± 6.3nmol/L after 8 weeks (p<0.01).
The total 25(OH)D was not different between the groups at baseline, but differed significantly between the groups after 4 and 8 weeks (p<0.001).

Conclusions: Vitamin D3 increases the total 25(OH)D concentration more than vitamin D2. Vitamin D2 supplementation was associated with a decrease in 25(OH)D3, which can explain the different effect on total 25(OH)D.

Received December 21, 2012.
Accepted August 18, 2013.

Copyright © 2013 by The Endocrine Society

See also VitaminDWiki