Funding sources This work was supported by grants from the Danish Medical Research Council (271-08-0461), the Danish Medical Association Research Fund, the Danish Dermatological Society, and Bispebjerg Hospital Research Fund.
A small suberythemal ultraviolet B dose every second week is sufficient to maintain summer vitamin D levels: a randomized controlled trial
Version of Record online: 23 JAN 2012
© 2011 The Authors. BJD © 2011 British Association of Dermatologists
British Journal of Dermatology
Volume 166, Issue 2, pages 430–433, February 2012
How to Cite
Bogh, M.K.B., Schmedes, A.V., Philipsen, P.A., Thieden, E. and Wulf, H.C. (2012), A small suberythemal ultraviolet B dose every second week is sufficient to maintain summer vitamin D levels: a randomized controlled trial. British Journal of Dermatology, 166: 430–433. doi: 10.1111/j.1365-2133.2011.10697.x
Conflicts of interest None declared.
- Issue online: 23 JAN 2012
- Version of Record online: 23 JAN 2012
- Accepted manuscript online: 20 OCT 2011 11:10AM EST
- Accepted for publication 14 October 2011
Background It is known that ultraviolet (UV) B radiation increases serum 25-hydroxyvitamin D3 [25(OH)D] level. However, there is uncertainty about the relationship between the maintenance of vitamin D status and UVB.
Objectives To define the frequency of UVB exposure necessary for maintaining summer 25(OH)D levels during the winter.
Methods In total, 60 participants were included from October 2008 to February 2009 (16 weeks) and randomized for UVB exposure of 1 standard erythema dose (SED) to ∼88% body area once a week (n = 15 completed), every second week (n = 14 completed) or every fourth week (n = 12 completed). The controls (n = 14 completed) had no intervention. Vitamin D was measured at baseline, every fourth week before exposure, and 2 days after the last UVB exposure.
Results The 25(OH)D levels (mean) after UVB exposure once a week increased significantly (from 71·9 to 84·5 nmol L−1) (P < 0·0001), whereas UVB exposure every second week maintained 25(OH)D levels (P = 0·16). A significant decrease in mean 25(OH)D levels (from 56·4 to 47·8 nmol L−1) (P < 0·0001) was found after UVB exposure once every fourth week and for the control group (from 64·8 to 40·1 nmol L−1) (P < 0·0001). The development in 25(OH)D levels during the 16-week study period were negatively correlated with baseline 25(OH)D (P < 0·0001). Further, the increase in 25(OH)D after the last UVB exposure was negatively correlated with the 25(OH)D level just before the last UVB exposure (P < 0·0001).
Conclusions Exposure to a UVB dose of 1 SED every second week to ∼88% body area is sufficient for maintaining summer 25(OH)D levels during the winter.