Previously published solar exposure guidelines for optimal vitamin D synthesis based on a study of skin samples may need to be revised, according to new research published today (September 27, 2021) in PNAS.
A study by researchers from King’s College London, with support from the NIHR Guy’s and St Thomas’ Biomedical Research Centre, has tested the optimum ultraviolet radiation (UVR) wavelengths for human skin production of vitamin D in sunlight.
UVR from sunlight can cause sunburn and skin cancer, however, it is the most important source of vitamin D that is essential for healthy bone development and maintenance.
Public health advice on sunlight exposure takes both risk and benefits into account. Calculating the potential risks and benefits from sunlight exposure is not simple because the health outcomes from UVR exposure vary considerably with wavelength within the sun’s UVR spectrum. For example, the sun’s UVR contains less than 5% short wavelength UVB radiation but this is responsible for over 80% of the sunburn response. Each health outcome from solar exposure has its own unique wavelength dependency.
The association between specific UVB wavelengths and vitamin D production was determined more than thirty years ago in skin samples (ex vivo). However, the finding is less well established and there have been doubts about its accuracy . These doubts compromise risk/benefit calculations for optimal solar exposure.