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Endocrine Care: N. Binkley, R. Novotny, D. Krueger, T. Kawahara, Y. G. Daida, G. Lensmeyer, B. W. Hollis, and M. K. Drezner Low Vitamin D Status despite Abundant Sun Exposure J Clin Endocrinol Metab 2007; 92: 2130-2135 [Abstract] [Full text] [PDF]

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Low vitamin D status despite abundant sun exposure.

Laura A. G. Armas, Marium Ilahi M.D., Robert P. Heaney M.D.   (3 August 2007)

Low vitamin D status despite abundant sun exposure. 3 August 2007
Laura A. G. Armas, Assistant Professor, Endocrinology & Metabolism Creighton University, Marium Ilahi M.D., Robert P. Heaney M.D. Send letter to journal: Re: Low vitamin D status despite abundant sun exposure. larmas{at}creighton.edu Laura A. G. Armas, et al.	Binkley et al. (1) show that even among highly sun exposed young people, there are individuals with low (<30 ng/mL) 25-hydroxyvitamin D (25(OH)D) levels as well as wide variability in 25(OH)D levels from 10 to 62 ng/mL. In their discussion, they offer some possible explanations for cutaneous differences in production, destruction or transport. We proposed that there could also be other differences in vitamin D and 25(OH)D metabolism influencing 25(OH)D status. In a recent investigation of the serum 25(OH)D response to a single, oral dose of 100,000 IU of cholecalciferol in 30 healthy adults, we noted a similar 6-fold range in response. Since the oral route bypassed any variable cutaneous production, we conclude than that differences in metabolism are responsible for most of the variability Binkley et al. (1) observed. We found a significant inverse correlation of Cmax and BMI (Spearman’s R, 2-tailed significance P < 0.01, with R2 = 0.466), but no correlation with baseline value (effectively eliminating regression to the mean as an important source of the observed variation). In our study about half of the variablity in response observed in our study was attributable to body size. Variation in the paper by Binkley et al. (1) may well have had a similar basis. Further studies need to be done to elucidate other causes (e.g., alleles of the D-binding proteins and 25-hydroxylase variations) of this large inter-individual variation in vitamin D metabolism. Reference 1.Binkley N, Novotny R, Krueger D, Kawahara T, Daida YG, Lensmeyer G, Hollis BW, Drezner MK. 2007. Low vitamin D status despite abundant sun exposure. J Clin Endocrinol Metab 92:2130-2135.