title: Vitamin D-binding protein, vitamin D status and serum bioavailable 25(OH)D of young Asian Indian males working in outdoor and indoor environments.
abstract: Urban Asian Indians generally have low serum 25(OH)D. Information on serum bioavailable 25(OH)D and the effect of prolonged sun-exposure in them is not known. We assessed serum 25(OH)D and bioavailable 25(OH)D in males with varying durations of sun-exposure in Delhi during August-September. Serum 25(OH)D, vitamin D-binding protein (DBP), bioavailable 25(OH)D, free 25(OH)D index, iPTH, ionized calcium and sun-index were assessed in outdoor, mixed outdoor-indoor and indoor workers (n = 88, 32 and 74, respectively). The mean sun-index (12.0 ± 6.25, 4.3 ± 2.20 and 0.7 ± 0.62, respectively; P < 0.001) was highest outdoors and lowest indoors. Serum 25(OH)D (29.0 ± 8.61, 19.1 ± 5.73 and 10.9 ± 4.19 ng/ml, respectively; P < 0.001), bioavailable 25(OH)D and free 25(OH)D index were maximum in outdoor workers followed by mixed-exposure and indoor workers. Their mean serum DBP levels (241.2 ± 88.77, 239.3 ± 83.40 and 216.6 ± 63.93 µg/ml, respectively; P = 0.12) were comparable. Mean serum iPTH was significantly lower in outdoor than indoor workers and showed inverse correlations with serum 25(OH)D, bioavailable 25(OH)D and free 25(OH)D index (r = -0.401, -0.269 and -0.236, respectively; P < 0.001 in all). Daily dietary-calorie intake was higher and calcium lower in outdoor than indoor workers. On regression analysis, sun-exposure was the only significant variable, increasing serum 25(OH)D by 2.03 ng/ml per hour of sun-exposure (95 % confidence interval 1.77-2.28; P < 0.001). Outdoor workers with prolonged sun-exposure were vitamin D-sufficient, with higher serum bioavailable 25(OH)D than the indoor workers during summer. Use of serum DBP levels did not affect the interpretation of their vitamin D status.
authors.affiliation: Department of Endocrinology and Metabolism, All India Institute of Medical Sciences, New Delhi, 110029, India. gosravinder@hotmail.com.
authors.forename: Ravinder
authors.initials: R
authors.lastname: Goswami
authors.affiliation: Department of Endocrinology and Metabolism, All India Institute of Medical Sciences, New Delhi, 110029, India.
authors.forename: Soma
authors.initials: S
authors.lastname: Saha
authors.affiliation: Department of Biostatistics, All India Institute of Medical Sciences, New Delhi, 110029, India.
authors.forename: Vishnubhatla
authors.initials: V
authors.lastname: Sreenivas
authors.affiliation: Department of Gastroenterology and Human Nutrition, All India Institute of Medical Sciences, New Delhi, 110029, India.
authors.forename: Namrata
authors.initials: N
authors.lastname: Singh
authors.affiliation: Department of Cardiac Biochemistry, All India Institute of Medical Sciences, New Delhi, 110029, India.
authors.forename: Ramakrishnan
authors.initials: R
authors.lastname: Lakshmy
mesh_terms: D000328:Adult; D002136:Calcium, Dietary / Q000008:administration & dosage; D006801:Humans; D007194:India; D008297:Male; D010281:Parathyroid Hormone / Q000097:blood; D012621:Seasons; D013472:Sunlight; D014807:Vitamin D / Q000097:blood*; D014809:Vitamin D-Binding Protein / Q000097:blood*; D044465:White People; D017132:Workplace; D055815:Young Adult
chemical_list: D002136:Calcium, Dietary; D010281:Parathyroid Hormone; D014809:Vitamin D-Binding Protein; D014807:Vitamin D
keywords: Asian Indians; Bioavailable 25(OH)D; Serum 25(OH)D; Sun-exposure; Vitamin D-binding protein
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