The authors state that they have no conflicts of interest.
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Research-Article
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Wintertime Vitamin D Supplementation Inhibits Seasonal Variation of Calcitropic Hormones and Maintains Bone Turnover in Healthy Men†
Article first published online: 13 OCT 2008
DOI: 10.1359/jbmr.081009
Copyright © 2009 ASBMR
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How to Cite
Viljakainen, H. T., Väisänen, M., Kemi, V., Rikkonen, T., Kröger, H., Laitinen, E. K. A., Rita, H. and Lamberg-Allardt, C. (2009), Wintertime Vitamin D Supplementation Inhibits Seasonal Variation of Calcitropic Hormones and Maintains Bone Turnover in Healthy Men. J Bone Miner Res, 24: 346–352. doi: 10.1359/jbmr.081009
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Publication History
- Issue published online: 4 DEC 2009
- Article first published online: 13 OCT 2008
- Manuscript Accepted: 7 OCT 2008
- Manuscript Revised: 3 SEP 2008
- Manuscript Received: 11 JAN 2008
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Keywords:
- vitamin D;
- PTH;
- ratio of TRACP to bone-specific alkaline phosphatase;
- pQCT;
- seasonal variation
Abstract
Vitamin D is suggested to have a role in the coupling of bone resorption and formation. Compared with women, men are believed to have more stable bone remodeling, and thus, are considered less susceptible to the seasonal variation of calcitropic hormones. We examined whether seasonal variation exists in calcitropic hormones, bone remodeling markers, and BMD in healthy men. Furthermore, we determined which vitamin D intake is required to prevent this variation. Subjects (N = 48) were healthy white men 21–49 yr of age from the Helsinki area with a mean habitual dietary intake of vitamin D of 6.6 ± 5.1 (SD) μg/d. This was a 6-mo double-blinded vitamin D intervention study, in which subjects were allocated to three groups of 20 μg (800 IU), 10 μg (400 IU), or placebo. Fasting blood samplings were collected six times for analyses of serum (S-)25(OH)D, iPTH, bone-specific alkaline phosphatase (BALP), and TRACP. Radial volumetric BMD (vBMD) was measured at the beginning and end of the study with pQCT. Wintertime variation was noted in S-25(OH)D, S-PTH, and S-TRACP (p < 0.001, p = 0.012, and p < 0.05, respectively) but not in S-BALP or vBMD in the placebo group. Supplementation inhibited the winter elevation of PTH (p = 0.035), decreased the S-BALP concentration (p < 0.05), but benefited cortical BMD (p = 0.09) only slightly. Healthy men are exposed to wintertime decrease in vitamin D status that impacts PTH concentration. Vitamin D supplementation improved vitamin D status and inhibited the winter elevation of PTH and also decreased BALP concentration. The ratio of TRACP to BALP shows the coupling of bone remodeling in a robust way. A stable ratio was observed among those retaining a stable PTH throughout the study. A daily intake of vitamin D in the range of 17.5–20 μg (700–800 IU) seems to be required to prevent winter seasonal increases in PTH and maintain stable bone turnover in young, healthy white men.