Changes in serum 25-hydroxyvitamin D and cholecalciferol after one whole-body exposure in a commercial tanning bed: a ra
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ORIGINAL ARTICLE
Changes in serum 25-hydroxyvitamin D and cholecalciferol after one whole-body exposure in a commercial tanning bed: a randomized study Jacob H. Langdahl • Louise Lind Schierbeck • Ulrich Christian Bang • Jens-Erik Beck Jensen
Received: 30 January 2012 / Accepted: 21 February 2012 / Published online: 6 March 2012 Ó Springer Science+Business Media, LLC 2012
Abstract We wanted to evaluate the cutaneous synthesis of 25OHD and cholecalciferol after one whole-body exposure to ultraviolet radiation type B (UVB) in a randomized setup. Healthy volunteers were randomized to one whole-body exposure in a commercial tanning bed with UVB emission (UVB/UVA ratio 1.8–2.0%) or an identical placebo tanning bed without UVB. The output in the 280–320 nm range was 450 lW/cm2. Blood samples were analyzed for 25OHD and cholecalciferol at baseline and during 7 days after treatment. We included 20 volunteers, 11 to UVB and 9 to placebo treatment. During the first 6 h, no significant differences in 25OHD between the groups were found. At the end of the study, we found a mean increase of 25OHD in the UVB group of 4.5 nmol/l (SD 7 nmol/l) compared to a decline of -1.2 nmol/l (SD 7 nmol/l) in the placebo group (p = 0.1). A linear mixed model yielded an increase of 25OHD in the UVB group of 1.0 nmol/l per 24 h (p \ 0.01). For cholecalciferol, we found a near significant increase of 1 pmol/l per hour in the UVB group compared to the placebo group during the first 6 h (p = 0.052). One tanning bed session had significant,
Electronic supplementary material The online version of this article (doi:10.1007/s12020-012-9641-z) contains supplementary material, which is available to authorized users. J. H. Langdahl J.-E. B. Jensen Faculty of Health Science, University of Copenhagen, Copenhagen, Denmark L. L. Schierbeck U. C. Bang (&) J.-E. B. Jensen Department of Endocrinology, Hvidovre Hospital, 541 Kettega˚rd Alle´ 30, 2650 Hvidovre, Denmark e-mail: [email protected]
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but modest impact on the level of 25OHD during 7 days after exposure to UVB. Keywords Ultraviolet rays 25-Hydroxyvitamin D Cholecalciferol Randomized controlled trial Ionized calcium Parathyroid hormone
Introduction Vitamin D plays an important role in the maintenance of the bone metabolism [1, 2]. However, in the recent 25 years, it has become clear that a variety of conditions may be related to hypovitaminosis D, including impaired glucose tolerance [3], cancer diseases [4], and schizophrenic disorders [5]. Vitamin D exists in various forms but only 25-hydroxyvitamin D (25OHD) and 1,25-dihydroxyvitamin D have known physiological properties. These metabolites are synthesized from cholecalciferol in the liver and kidney, and the main sources of cholecalciferol are food and cutaneous synthesis. In the skin, 7-dehydrocholesterol metabolizes to pre-vitamin D and then to cholecalciferol when exposed to ultraviolet radiation type B (UVB). From the subcutaneous tissue, it enters the bloodstream and is transported to the liver for further metabolism
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