Sun exposure guidelines may need to be revised, researchers warn

According to a new study published today in PNAS.

A study conducted by researchers at King’s College London, with support from NIHR Guy’s and St Thomas’ Biomedical Research Center, tested the optimal wavelengths of ultraviolet (UV) radiation for vitamin D production by human skin under the sun.

UV rays from the sun can cause sunburn and skin cancer. However, it is the most important source of vitamin D, which is essential for the development and maintenance of healthy bones.

Public health advice on sun exposure takes into account both the risks and the benefits. Calculating the potential risks and benefits of sun exposure is not straightforward because the health effects of UV exposure vary greatly with wavelength in the sun’s UV spectrum. For example, the sun’s UV rays contain less than 5% short-wavelength UVB radiation, but they are responsible for over 80% of the response to sunburn. Each health result from sun exposure has its own wavelength dependence.

The association between specific UVB wavelengths and vitamin D production was determined over thirty years ago in skin samples (ex vivo). However, the conclusion is less well established and there have been doubts as to its accuracy. These doubts compromise the risk / benefit calculations for optimal solar exposure.

Researchers led by Professor Antony Young of King’s College London measured blood levels of vitamin D in 75 healthy young volunteers before, during and after partial or full body exposure to five different artificial UVR sources with varying amounts of UVB radiation, to weigh the trade-off between the benefits of sun exposure, including the synthesis of vitamin D, and the risks of sunburn and skin cancer.

They then compared their results with those that would be predicted from the old ex vivo study on vitamin D and found that the previous study is not an accurate predictor of the benefits of UV exposure.

The authors recommend a simple systematic correction of the ex vivo wavelength dependence for vitamin D. New study means many risk-benefit calculations for solar UV exposure need to be revised with a revised version of wavelength dependence for vitamin D.

Professor Antony Young said: “Our study shows that the calculations of the risks versus the benefits of sun exposure may need to be re-evaluated. The results of the study are timely as the global technical committee, the International Commission on Illumination, which defines UVR standards, will be able to discuss the results of this article to reassess wavelength dependence. vitamin D. Further research from our group will determine the risk / benefit calculations.