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The Vitamin D Debate: Translating Controlled Experiments into Reality for Human Sun Exposure Times

Authors

  • Ann R. Webb,

    Corresponding author
    1. School of Earth Atmospheric and Environmental Sciences, University of Manchester, Manchester, UK
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  • Richard Kift,

    1. School of Earth Atmospheric and Environmental Sciences, University of Manchester, Manchester, UK
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  • Jacqueline L. Berry,

    1. Vitamin D Research Laboratory, School of Biomedical Sciences, University of Manchester, Manchester Royal Infirmary, Manchester, UK
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  • Lesley E. Rhodes

    1. Photobiology Unit, Dermatological Sciences, School of Translational Medicine, University of Manchester, Manchester Academic Health Science Centre, Salford Royal NHS Foundation Hospital, Manchester, UK
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Corresponding author email: ann.webb@manchester.ac.uk (Ann R. Webb)

Abstract

Exposure to sunlight, specifically the ultraviolet radiation, has both positive and negative health effects. Maximizing the benefits (vitamin D synthesis) while minimizing the damage is a multifaceted problem in which many of the elements are poorly quantified. Here we show how rigorously conducted large sample size laboratory studies of the effect of ultraviolet radiation dose on vitamin D status can be applied to real-life situations. This was achieved by modeling the radiation incident on different surfaces for different solar locations, and equating with the controlled exposures in the laboratory studies. Results from both model and experimental data show that relatively short exposures of a modest amount of unprotected skin to summer sunlight in northern climes, on a regular basis during lunchtime hours, increases vitamin D to sufficiency status (≥20 ng mL−1) in the white Caucasian population. While both sun exposure conditions and human skin responses are variable in real life, these quantitative findings provide a guide for authorities devising sunlight exposure recommendations.

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