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Physical Determinants of Vitamin D Photosynthesis: A Review

Research output: Contribution to journalArticlepeer-review

Jonathan J. Neville, Tommaso Palmieri, Antony R. Young

Original languageEnglish
Article numbere10460
JournalJBMR Plus
Volume5
Issue number1
DOIs
Accepted/In press2021
PublishedJan 2021

Bibliographical note

Funding Information: We thank Drs Arjan van Dijk, Germar Bernhard, and Richard McKenzie for their valuable comments during the preparation of this review. We also thank Dr Andrew Noymer for allowing us to use Fig. 4, Dr Peter Philipsen for generating the data for Fig. 3, and Dr Karl Lawrence for preparing the figures. Authors' Roles: ARY conceived the idea for the paper and oversaw its writing and revision. JJN sourced the literature and wrote the first draft. TP assisted with the editing and specifically researched the literature on the effects of UVR dose and body surface area on vitamin D responses. Publisher Copyright: © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research. Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

King's Authors

Abstract

Vitamin D synthesis by exposure of skin to solar ultraviolet radiation (UVR) provides the majority of this hormone that is essential for bone development and maintenance but may be important for many other health outcomes. This process, which is the only well-established benefit of solar UVR exposure, depends on many factors including genetics, age, health, and behavior. However, the most important factor is the quantity and quality of UVR reaching the skin. Vitamin D synthesis specifically requires ultraviolet B (UVB) radiation that is the minority component (<5%) of solar UVR. This waveband is also the most important for the adverse effects of solar exposure. The most obvious of which is sunburn (erythema), but UVB is also the main cause of DNA damage to the skin that is a prerequisite for most skin cancers. UVB at the Earth's surface depends on many physical and temporal factors such as latitude, altitude, season, and weather. Personal, cultural, and behavioral factors are also important. These include skin melanin, clothing, body surface area exposed, holiday habits, and sunscreen use. There is considerable disagreement in the literature about the role of some of these factors, possibly because some studies have been done by researchers with little understanding of photobiology. It can be argued that vitamin D supplementation obviates the need for solar exposure, but many studies have shown little benefit from this approach for a wide range of health outcomes. There is also increasing evidence that such exposure offers health benefits independently of vitamin D: the most important of which is blood-pressure reduction. In any case, public health advice must optimize risk versus benefit for solar exposure. It is fortunate that the individual UVB doses necessary for maintaining optimal vitamin D status are lower than those for sunburn, irrespective of skin melanin.

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