Sunlight exposure guidelines may need to be revised

Date:
September 27, 2021
Source:
King's College London
Summary:
Previously published solar exposure guidelines for optimal vitamin
D synthesis based on a study of skin samples may need to be revised.



FULL STORY ========================================================================== 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 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.

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

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

The authors recommend a simple systematic correction of the ex vivo
wavelength dependency for vitamin D. The new study means that many risk
benefit calculations for solar UVR exposure must be reviewed with a
revised version of the wavelength dependency for vitamin D.

Professor Antony Young said: "Our study shows that risk versus benefit calculations from solar exposure may need to be re-evaluated. The
results from the study are timely because the global technical
committee, Commission internationale de l'e'clairage, that sets
UVR standards will be able to discuss the findings of this paper
to re-evaluate the wavelength dependency of vitamin D. Further
research from our group will determine the risk/benefit calculations." ========================================================================== Story Source: Materials provided by King's_College_London. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Antony R. Young, Kylie A. Morgan, Graham I. Harrison, Karl
P. Lawrence,
Bibi Petersen, Hans Christian Wulf, Peter A. Philipsen. A revised
action spectrum for vitamin D synthesis by suberythemal UV radiation
exposure in humans in vivo. Proceedings of the National Academy of
Sciences, 2021; 118 (40): e2015867118 DOI: 10.1073/pnas.2015867118 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210927150523.htm

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