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UV production of Vitamin D varies with the individual – 2010

Journal of Investigative Dermatology (2010) 130, 1411–1418; doi:10.1038/jid.2009.417; published online 14 January 2010
Lesley E Rhodes1, Ann R Webb2, Heather I Fraser1, Richard Kift2, Marie T Durkin1, Donald Allan1, Sarah J O'Brien3, Andy Vail4 and Jacqueline L Berry5
1 Photobiology Unit, Dermatological Sciences, School of Translational Medicine, University of Manchester, Manchester Academic Health Science Centre, Salford Royal NHS Foundation Hospital, Manchester, UK
2 School of Earth Atmospheric and Environmental Sciences, University of Manchester, Manchester, UK
3 Occupational and Environmental Health Research Group, School of Translational Medicine, University of Manchester, Manchester, UK
4 Health Methodology Research Group, School of Community Based Medicine, University of Manchester, Manchester, UK
5 Vitamin D Research Laboratory, Endocrine Sciences Research Group, School of Clinical and Laboratory Sciences, University of Manchester, Manchester Academic Health Science Centre, Manchester Royal Infirmary, Manchester, UK
Correspondence: Lesley E. Rhodes, Photobiology Unit, Dermatological Sciences, University of Manchester, Salford Royal NHS Foundation Hospital, Manchester, M6 8HD, UK. E-mail: lesley.e.rhodes at manchester.ac.uk

Recommendations on limitation of summer sunlight exposure to prevent skin cancer may conflict with requirements to protect bone health through adequate vitamin D levels, the principal source being UVB in summer sunlight. We determined whether sufficient (greater than or equal to 20 ng ml−1) and proposed optimal (greater than or equal to 32 ng ml−1) 25(OH)D levels are attained by following UK guidance advising casual short exposures to UVB in summer sunlight, and performed the study under known conditions to enhance the specificity of future recommendations.
During wintertime, when ambient UVB is negligible, 120 white Caucasians, aged 20–60 years, from Greater Manchester, UK (53.5°N) received a simulated summer's sunlight exposures, specifically 1.3 standard erythemal dose, three times weekly for 6 weeks, while wearing T-shirt and shorts.
The baseline winter data predict that 5% (confidence interval (CI): 2.7–8.6) of Greater Manchester white Caucasians have deficient (<5 ng ml−1) 25(OH)D, 62.5% (CI: 55.2–69.4) have insufficient, and only 2.9% (CI: 1.4–5.6) have proposed optimal levels. After the simulated summer exposures, 90 (CI: 84.9–93.7) and 26.2% (CI: 20.1–33.2) reached 20 and 32 ng ml−1 25(OH)D, respectively. Assuming midday UVB levels, sufficient but suboptimal vitamin D status is attained after a summer's short (13 minutes) sunlight exposures to 35% skin surface area; these findings will assist future public health guidance on vitamin D acquisition.

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Need more UV time for 20+ reasons - such as dark skin, obese, senior, more clothes, standing up, etc.
See also VitaminDWiki

35% of whole body?
They used a whole body irradiation cabinet with people clothed with t-shirt and shorts
Wonder if they noticed that a person lying down only has 1/2 of the body exposed to the sun?

Note: you can increase skin exposed to UV by wearing t-shirts and shorts which only reduce the UV by half

Attached files

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4740 Rhodes T4.jpg admin 16 Dec, 2014 60.53 Kb 1090
4738 Rhodes 2010.pdf admin 16 Dec, 2014 369.10 Kb 1200