Vitamin D supplementation in early childhood and risk of type 1 diabetes: a systematic review and meta-analysis
- 1Department of Paediatrics, Stockport NHS Foundation Trust, Stockport, UK
- 2Department of Paediatric Gastroenterology, Central Manchester and Manchester Children’s University Hospitals, Booth Hall Children’s Hospital, Manchester, UK
- C S Zipitis, Department of Paediatrics, Stockport NHS Foundation Trust, Poplar Grove, Stockport SK2 7JE, UK;
- Accepted 17 January 2008
- Published Online First 13 March 2008
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.
Contributors: CSZ (guarantor) and AKA were both responsible for study selection, data extraction, validity assessment, data interpretation and writing the paper.
Competing interests: None.
Ethics approval: Not required.