C16
Can adequate vitamin D levels be achieved in the UK by following national recommendations on summer sunlight exposure?
Lesley Rhodes, Ann Webb, Heather Fraser, Richard Kift, Marie Durkin, Donald Allan, Sarah O'Brien, Andrew Vail, Jacqueline Berry
University of Manchester, UK
Background
Vitamin D is essential for bone health and there is accumulating evidence of its chemopreventive properties. A potential health conflict arises since the major source of vitamin D is cutaneous synthesis following exposure to ultraviolet radiation (UVR) in sunlight, while UVR is also the principal cause of most skin cancers. Our objectives were to examine if adequate vitamin D status is attained by following national recommendations (Health Protection Agency; Cancer Research UK SunSmart campaign) on summer sunlight exposure i.e. casual short sub-erythemal exposures, and to provide data to inform more specific guidance by performing the study under controlled UV dose and skin surface area conditions.
Method
120 white Caucasians aged 20-60y were given a course of UV treatments to mimic a summer seasons exposures achieved through following national guidance. The source was a whole body irradiation cabinet fitted with a combination of Arimed B (Cosmedico, Germany) and Cleo Natural (Philips, The Netherlands) fluorescent tubes (95% UVA: 320-400 nm, 5% UVB: 290-320 nm). The pre-vitamin D irradiance of the lamps, i.e. the biologically relevant quantity, is very similar to, and approximately twice, that of a clear June day in Manchester (latitude 53) at noon. The study was performed in January/February to avoid confounding by ambient UVR, and the sample size was selected for prediction of outcomes for a wider white Caucasian population. Primary outcome measure was % population reaching circulating 25(OH)D3 levels designated sufficient for bone health (≥20 ng/ml), and a further outcome measure was % population reaching levels proposed as optimal for health (≥32 ng/ml), after the simulated summer exposures.
Results
Our data predict that only 262% (95% CI 201 to 332) of the Greater Manchester white Caucasian population reach optimal 25(OH)D3 levels, while 90% (95% CI 84.9 to 93.7) achieve levels for sufficiency immediately following a summer season of short sunlight exposures, specifically 13 minutes midday exposure, 3 times weekly for 6 weeks, while wearing casual clothing to reveal 33% skin surface area.
Conclusion
These findings will assist future recommendations on summer sunlight exposure.
Acknowledgements
This project was funded by Cancer Research UK
