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

• Published in: The American journal of clinical nutrition Vol. 97; no. 6; pp. 1210 - 1216
• Main Authors: Farrar, Mark D, Webb, Ann R, Kift, Richard, Durkin, Marie T, Allan, Donald, Herbert, Annie, Berry, Jacqueline L, Rhodes, Lesley E
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Clinical Nutrition 01.06.2013; American Society for Nutrition; American Society for Clinical Nutrition, Inc
• Subjects: Adult; Adults; Asian people; Asian People - ethnology; Asians; Biological and medical sciences; blood serum; clinical nutrition; Diet; dose response; Dose-Response Relationship, Radiation; erythema; Erythema - physiopathology; Ethnicity; Feeding. Feeding behavior; Female; Fundamental and applied biological sciences. Psychology; Guidelines as Topic; Humans; latitude; Male; Middle Aged; Nutritional Status; osteomalacia; Parathyroid Hormone - blood; rickets; Rickets - blood; Rickets - etiology; Seasons; Simulation; Skin - metabolism; Skin - radiation effects; solar radiation; summer; Sunlight; Treatment Outcome; Ultraviolet radiation; Ultraviolet Rays; United Kingdom; United Kingdom - epidemiology; Vertebrates: anatomy and physiology, studies on body, several organs or systems; Vitamin D; Vitamin D - administration & dosage; Vitamin D - blood; Vitamin D Deficiency - blood; Vitamin D Deficiency - complications; Vitamin D Deficiency - ethnology; vitamin status; Young Adult; United Kingdom; United Kingdom > UK; Micronutrient; South; Vitamin D; Sun
• ISSN: 0002-9165; 1938-3207; 1938-3207
• DOI: 10.3945/ajcn.112.052639

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.