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Open Access Research article

Changes in the vitamin D endocrine system and bone turnover after oral vitamin D3 supplementation in healthy adults: results of a randomised trial

Kristin Holvik124*, Ahmed A Madar2, Haakon E Meyer12, Cathrine M Lofthus3 and Lars C Stene1

Author Affiliations

1 Division of Epidemiology, Norwegian Institute of Public Health, Oslo, Norway

2 Institute of Health and Society, University of Oslo, Oslo, Norway

3 Department of Endocrinology, Oslo University Hospital, Oslo, Norway

4 Norwegian Institute of Public Health, P.O. Box 4404, Nydalen, 0403, Oslo, Norway

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BMC Endocrine Disorders 2012, 12:7  doi:10.1186/1472-6823-12-7

Published: 13 June 2012

Abstract

Background

There is uncertainty as to which intake of vitamin D is needed to suppress PTH and maintain normal bone metabolism throughout winter at northern latitudes. We aimed to investigate whether four weeks’ daily supplementation with 10 μg vitamin D3 from fish oil produced a greater change in serum vitamin D metabolites, parathyroid hormone, and bone turnover in healthy adults compared with solid multivitamin tablets. Furthermore, it was studied whether age, gender, ethnic background, body mass index, or serum concentrations at baseline predicted the magnitude of change in these parameters.

Methods

Healthy adults aged 19–48 years living in Oslo, Norway (59°N) were randomised to receive a daily dose of 10 μg vitamin D3 given as fish oil capsules or multivitamin tablets during four weeks in late winter. Serum samples from baseline and after 28 days were analysed for 25-hydroxyvitamin D (s-25(OH)D), 1,25-dihydroxyvitamin D (s-1,25(OH)2D), intact parathyroid hormone (s-iPTH), and osteoclast-specific tartrate-resistant acid phosphatase 5b (s-TRACP). Fifty-five eligible participants completed the intervention (74% of those randomised).

Results

S-25(OH)D increased by mean 34.1 (SD 13.1) nmol/l, p < 0.001; s-iPTH decreased by mean 1.2 (SD 2.5) pmol/l, p = 0.001; s-1,25(OH)2D increased by mean 13 (SD 48) pmol/l, p = 0.057; and s-TRACP increased by mean 0.38 (SD 0.33) U/l, p < 0.001. For all these parameters, there was no difference between fish oil and multivitamin formulation. Baseline concentrations were the only independent predictors of changes in biochemical parameters.

Conclusions

Four weeks of daily supplementation with 10 μg vitamin D3 decreased mean s-iPTH and increased s-TRACP concentration, and this did not differ by mode of administration. Our results suggest an increased bone resorption following vitamin D supplementation in young individuals, despite a decrease in parathyroid hormone levels.

Trial Registration

ClinicalTrials.gov: NCT01482689

Keywords:
Supplementation; Randomised trial; Vitamin D3; Cholecalciferol; 25-hydroxyvitamin D; 1,25-dihydroxyvitamin D; Parathyroid hormone; Tartrate-resistant acid phosphatase; Bone turnover