Recommended summer sunlight exposure levels can produce sufficient (> or =20 ng ml(-1)) but not the proposed optimal (> or =32 ng ml(-1)) 25(OH)D levels at UK latitudes.
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 (> or =20 ng ml(-1)) and proposed optimal (> or =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 degrees 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.
Rhodes
Lesley E
LE
Photobiology Unit, Dermatological Sciences, School of Translational Medicine, University of Manchester, Manchester Academic Health Science Centre, Salford Royal NHS Foundation Hospital, Manchester, UK. lesley.e.rhodes@manchester.ac.uk
Webb
Ann R
AR
Fraser
Heather I
HI
Kift
Richard
R
Durkin
Marie T
MT
Allan
Donald
D
O'Brien
Sarah J
SJ
Vail
Andy
A
Berry
Jacqueline L
JL
D000328:Adult; D001842:Bone and Bones / Q000378:metabolism; D004307:Dose-Response Relationship, Radiation; D004781:Environmental Exposure; D005260:Female; D017408:Guidelines as Topic; D006801:Humans; D008297:Male; D008875:Middle Aged; D012621:Seasons; D012867:Skin / Q000378:metabolism* / Q000528:radiation effects*; D012878:Skin Neoplasms / Q000517:prevention & control*; D013472:Sunlight; D013997:Time Factors; D014466:Ultraviolet Rays; D006113:United Kingdom; D014807:Vitamin D / Q000096:biosynthesis / Q000097:blood; D044465:White People; D055815:Young Adult
D014807:Vitamin D