Serum vitamin D levels are lower in Australian children and adolescents with type 1 diabetes than in children without diabetes

Authors

  • Ristan M Greer,

    Corresponding author
    • Queensland Children's Medical Research Institute, Royal Children's Hospital, The University of Queensland, Herston, Queensland, Australia
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  • Sharon L Portelli,

    1. Discipline of Paediatrics and Child Health, Royal Children's Hospital, University of Queensland, Herston, Queensland, Australia
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  • Betsy Shin-Min Hung,

    1. Discipline of Paediatrics and Child Health, Royal Children's Hospital, University of Queensland, Herston, Queensland, Australia
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  • Geoffrey J Cleghorn,

    1. School of Medicine, University of Queensland, Herston, Queensland, Australia
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  • Sarah K McMahon,

    1. Department of Endocrinology and Diabetes, Royal Children's Hospital, Herston, Queensland, Australia
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  • Jennifer A Batch,

    1. Department of Endocrinology and Diabetes, Royal Children's Hospital, Herston, Queensland, Australia
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  • Louise S Conwell

    1. Queensland Children's Medical Research Institute, Royal Children's Hospital, The University of Queensland, Herston, Queensland, Australia
    2. Discipline of Paediatrics and Child Health, Royal Children's Hospital, University of Queensland, Herston, Queensland, Australia
    3. Department of Endocrinology and Diabetes, Royal Children's Hospital, Herston, Queensland, Australia
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Corresponding author: Ristan M Greer, PhD MVSc BA MACVSc

Queensland Children's Medical Research Institute, Royal Children's Hospital, The University of Queensland

Herston, Queensland 4029, Australia.

Tel: 61 7 3636 1294

fax: 61 7 3862 9792

e-mail: r.greer@uq.edu.au

Abstract

Vitamin D is synthesised in the skin through the action of UVB radiation (sunlight), and 25-hydroxy vitamin D (25OHD) measured in serum as a marker of vitamin D status. Several studies, mostly conducted in high latitudes, have shown an association between type 1 diabetes mellitus (T1DM) and low serum 25OHD. We conducted a case–control study to determine whether, in a sub-tropical environment with abundant sunlight (latitude 27.5°S), children with T1DM have lower serum vitamin D than children without diabetes. Fifty-six children with T1DM (14 newly diagnosed) and 46 unrelated control children participated in the study. Serum 25OHD, 1,25-dihydroxy vitamin D (1,25(OH)2D) and selected biochemical indices were measured. Vitamin D receptor (VDR) polymorphisms Taq1, Fok1, and Apa1 were genotyped. Fitzpatrick skin classification, self-reported daily hours of outdoor exposure, and mean UV index over the 35 d prior to blood collection were recorded. Serum 25OHD was lower in children with T1DM (n = 56) than in controls (n = 46) [mean (95%CI) = 78.7 (71.8–85.6) nmol/L vs. 91.4 (83.5–98.7) nmol/L, p = 0.02]. T1DM children had lower self-reported outdoor exposure and mean UV exposure, but no significant difference in distribution of VDR polymorphisms. 25OHD remained lower in children with T1DM after covariate adjustment. Children newly diagnosed with T1DM had lower 1,25(OH)2D [median (IQR) = 89 (68–122) pmol/L] than controls [121 (108–159) pmol/L, p = 0.03], or children with established diabetes [137 (113–153) pmol/L, p = 0.01]. Children with T1DM have lower 25OHD than controls, even in an environment of abundant sunlight. Whether low vitamin D is a risk factor or consequence of T1DM is unknown.

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