Efficacy of a dose range of simulated sunlight exposures in raising vitamin D status in South Asian adults: implications for targeted guidance on sun exposure
Am J Clin Nutr June 2013 vol. 97 no. 6 1210-1216
Mark D Farrar, Ann R Webb, Richard Kift, Marie T Durkin, Donald Allan, Annie Herbert, Jacqueline L Berry, and Lesley E Rhodes
Dermatology Centre, Institute of Inflammation and Repair (MDF, MTD, DA, and LER), and the Institute of Population Health (AH), University of Manchester, Manchester Academic Health Science Centre, Salford Royal National Health Service Foundation Trust, Manchester, United Kingdom; the School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, United Kingdom (ARW and RK); and the Endocrinology and Diabetes Research Group, Institute of Human Development, University of Manchester, Manchester Academic Health Science Centre, Manchester Royal Infirmary, Manchester, United Kingdom (JLB).
Supported by Cancer Research UK (grant C20668/A10007).
Address correspondence to LE Rhodes, Photobiology Unit, Dermatology Centre, University of Manchester, Salford Royal National Health Service Foundation Trust, Manchester M6 8HD, United Kingdom. E-mail: lesley.e.rhodes at manchester.ac.uk.
Background: Vitamin D is essential for bone health, and cutaneous synthesis is an important source. South Asians cannot attain adequate amounts of vitamin D by following general recommendations on summer sunlight exposure at northerly latitudes, and increased exposure may be appropriate for improving their vitamin D status.
Objective: We examined the efficacy of a dose range of simulated summer sunlight exposures in raising vitamin D status in UK adults of South Asian ethnicity.
Design: In a dose-response study, healthy adults of South Asian ethnicity (n = 60; 20–60 y old) received 1 of 6 ultraviolet exposures ranging from 0.65 to 3.9 standard erythema doses (SEDs), which were equivalent to 15–90 min unshaded noontime summer sunlight at 53.5°N (Manchester, United Kingdom), 3 times/wk for 6 wk, while wearing casual clothes that revealed a 35% skin area. Serum 25-hydroxyvitamin D [25(OH)D] was measured weekly, and dietary vitamin D was estimated.
Results: At baseline, all completing participants (n = 51) were vitamin D insufficient [25(OH)D concentrations <20 ng/mL], and a high proportion of participants were deficient [35% of subjects had 25(OH)D concentrations <5 ng/mL], and 90% of subjects had 25(OH)D concentrations <10 ng/mL, which are concentrations at which osteomalacia and rickets occur). The 25(OH)D concentration rose significantly in all dose groups. Postcourse, all participants achieved 25(OH)D concentrations ≥5 ng/mL, whereas only 6 subjects attained 25(OH)D concentrations ≥20 ng/mL. Participants who received exposures ≥1.95 SEDs (equivalent to 45 min unshaded sunlight; n = 33) attained a mean (±SD) 25(OH)D concentration of 15.7 ± 5 ng/mL (mean rise: 8.7 ± 5.7 ng/mL; 95% CI: 6.8, 10.6 ng/mL; P < 0.001), and 94% of subjects achieved concentrations >10 ng/mL.
Conclusions: Targeted guidance on sunlight exposure could usefully enhance vitamin D status to avoid deficiency [25(OH)D concentration >10 ng/mL] in South Asians living at latitudes distant from the equator. This trial was registered at the ISRCTN Register (www.isrctn.org) as 07565297.
Received November 18, 2012. Accepted March 25, 2013.
- 60 subjects with type 5 skin, 35% skin area, 6 weeks
- 6 UV levels
- Probably 10 subjects got 90 minutes of noon sun 3 days a week
- 40% of those did not get to even 20 ng
- 20 ng is great in the UK, since the recommended level is a meager 10 ng
Interesting delay: Published results in June 2013, yet the trial was completed 4 years before
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