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Updated: May 28, 2026
Minimal Erythema Dose (MED) Testing
Published on: May 28, 2013
A small suberythemal ultraviolet B dose every second week is sufficient to maintain summer vitamin D levels: a
M K B Bogh1, A V Schmedes, P A Philipsen
1Department of Dermatology, Copenhagen University Hospital, Bispebjerg, Bispebjerg Bakke 23, 2400 Copenhagen NV, Denmark. bogh@dadlnet.dk
Background:
It is known that ultraviolet (UV) B radiation increases serum 25-hydroxyvitamin D(3) [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 (16weeks) 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 2days after the last UVB exposure.
Results:
The 25(OH)D levels (mean) after UVB exposure once a week increased significantly (from 71·9 to 84·5nmolL(-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 47·8nmolL(-1) ) (P<0·0001) was found after UVB exposure once every fourth week and for the control group (from 64·8 to 40·1nmolL(-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.
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