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Vitamin D supplementation in early childhood and risk of type 1 diabetes: a systematic review and meta-analysis
  1. C S Zipitis1,
  2. A K Akobeng2
  1. 1
    Department of Paediatrics, Stockport NHS Foundation Trust, Stockport, UK
  2. 2
    Department of Paediatric Gastroenterology, Central Manchester and Manchester Children’s University Hospitals, Booth Hall Children’s Hospital, Manchester, UK
  1. C S Zipitis, Department of Paediatrics, Stockport NHS Foundation Trust, Poplar Grove, Stockport SK2 7JE, UK; czipitis{at}hotmail.com

Abstract

Objectives: To assess whether vitamin D supplementation in infancy reduces the risk of type 1 diabetes in later life.

Methods: This was a systematic review and meta-analysis using Medline, Embase, Cinahl, Cochrane Central Register of Controlled Trials and reference lists of retrieved articles. The main outcome measure was development of type 1 diabetes. Controlled trials and observational studies that had assessed the effect of vitamin D supplementation on risk of developing type 1 diabetes were included in the analysis.

Results: Five observational studies (four case-control studies and one cohort study) met the inclusion criteria; no randomised controlled trials were found. Meta-analysis of data from the case-control studies showed that the risk of type 1 diabetes was significantly reduced in infants who were supplemented with vitamin D compared to those who were not supplemented (pooled odds ratio 0.71, 95% CI 0.60 to 0.84). The result of the cohort study was in agreement with that of the meta-analysis. There was also some evidence of a dose-response effect, with those using higher amounts of vitamin D being at lower risk of developing type 1 diabetes. Finally, there was a suggestion that the timing of supplementation might also be important for the subsequent development of type 1 diabetes.

Conclusion: Vitamin D supplementation in early childhood may offer protection against the development of type 1 diabetes. The evidence for this is based on observational studies. Adequately powered, randomised controlled trials with long periods of follow-up are needed to establish causality and the best formulation, dose, duration and period of supplementation.

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Footnotes

  • Contributors: CSZ (guarantor) and AKA were both responsible for study selection, data extraction, validity assessment, data interpretation and writing the paper.

  • Funding: None.

  • Competing interests: None.

  • Ethics approval: Not required.

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