期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2021
卷号：118
期号：40
DOI：10.1073/pnas.2015867118
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：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.
Action spectra are important biological weighting functions for risk/benefit analyses of ultraviolet (UV) radiation (UVR) exposure. One important human benefit of exposure to terrestrial solar UVB radiation (∼295 to 315 nm) is the cutaneous synthesis of vitamin D
3 that is initiated by the photoconversion of 7-dehydrocholesterol to previtamin D
3. An action spectrum for this process that is followed by other nonphotochemical steps to achieve biologically active vitamin D
3 has been established from ex vivo data and is widely used, although its validity has been questioned. We tested this action spectrum in vivo by full- or partial-body suberythemal irradiation of 75 healthy young volunteers with five different polychromatic UVR spectra on five serial occasions. Serum 25-hydroxyvitamin D
3 [25(OH)D
3] levels, as the most accurate measure of vitamin D
3 status, were assessed before, during, and after the exposures. These were then used to generate linear dose–response curves that were different for each UVR spectrum. It was established that the previtamin D
3 action spectrum was not valid when related to the serum 25(OH)D
3 levels, as weighting the UVR doses with this action spectrum did not result in a common regression line unless it was adjusted by a blue shift, with 5 nm giving the best fit. Such a blue shift is in accord with the published in vitro action spectra for vitamin D
3 synthesis. Thus, calculations regarding the risk (typically erythema) versus the benefit of exposure to solar UVR based on the ex vivo previtamin D
3 action spectrum require revision.
