A revised action spectrum for vitamin D synthesis by suberythemal UV radiation exposure in humans in vivo
Antony R. Young, K Morgan, Graham I. Harrison, Karl Lawrence, B. Petersen, Hans Christian Wulf, Peter A. Philipsen
Abstract
Significance Solar UV radiation (UVR) causes sunburn but initiates the first step of vitamin D synthesis, which is the formation of previtamin D 3 (pre-D 3 ) in skin. The gold standard for assessing vitamin D is serum 25-hydroxyvitamin D 3 [25(OH)D 3 ]. Public health advice for optimal solar exposure requires UVR wavelength-dependence (action spectrum) data on risks and benefits. An action spectrum for pre-D 3 in human ex vivo skin was established over 30 y ago, but its validity has been questioned. We tested this action spectrum in healthy volunteers using serum 25(OH)D 3 as the endpoint. Our analysis shows that the pre-D 3 action spectrum can be improved with a systematic correction. This will result in better risk–benefit calculations for public health advice on solar exposure.