title: MANAGEMENT OF ENDOCRINE DISEASE: The effect of vitamin D supplementation on glycaemic control in patients with type 2 diabetes mellitus: a systematic review and meta-analysis.
abstract: OBJECTIVE
  Epidemiologic studies suggest that vitamin D status plays a role in glycaemic control in patients with type 2 diabetes. However, intervention studies yielded inconsistent results. The aim of this study is to systematically review the effect of vitamin D supplementation on glycaemic control in patients with type 2 diabetes.
  
  
  METHODS
  Systematic review and meta-analysis. We searched Medline, Embase and the Cochrane Library for RCTs examining the effect of vitamin D supplementation on glycaemic control in patients with type 2 diabetes. A random-effects model meta-analysis was performed to obtain a summarized outcome of vitamin D supplementation on HbA1c, fasting glucose and homeostasis model assessment - insulin resistance (HOMA-IR).
  
  
  RESULTS
  Twenty-three RCTs were included in this systematic review representing a total of 1797 patients with type 2 diabetes. Mean (± s.d.) change in serum 25-hydroxyvitamin D varied from 1.8 ± 10.2 nmol/L to 80.1 ± 54.0 nmol/L. Nineteen studies included HbA1cas outcome variable. Combining these studies no significant effect in change of HbA1cwas seen after vitamin D intervention compared with placebo. A significant effect of vitamin D supplementation was seen on fasting glucose in a subgroup of studies (n = 4) with a mean baseline HbA1c≥ 8% (64 mmol/mol) (standardized difference in means: 0.36; 95% CI: 0.12-0.61, P = 0.003).
  
  
  CONCLUSIONS
  Current evidence of RCTs does not support short-term vitamin D supplementation in a heterogeneous population with type 2 diabetes. However, in patients with poorly controlled diabetes, a favourable effect of vitamin D is seen on fasting glucose.
authors.affiliation: Department of Internal MedicineMedical Centre Alkmaar, Alkmaar, The Netherlands.
authors.forename: Yvonne H M
authors.initials: YH
authors.lastname: Krul-Poel
authors.affiliation: Department of Epidemiology and BiostatisticsVU University Medical Centre, Amsterdam, The Netherlands.
authors.forename: Marieke M
authors.initials: MM
authors.lastname: Ter Wee
authors.affiliation: Department of Epidemiology and BiostatisticsVU University Medical Centre, Amsterdam, The Netherlands.
authors.forename: Paul
authors.initials: P
authors.lastname: Lips
authors.affiliation: Department of Internal MedicineMedical Centre Alkmaar, Alkmaar, The Netherlands s.simsek@nwz.nl.
authors.forename: Suat
authors.initials: S
authors.lastname: Simsek
mesh_terms: D000818:Animals; D001786:Blood Glucose / Q000187:drug effects; D003924:Diabetes Mellitus, Type 2 / Q000097:blood* / Q000188:drug therapy*; D004700:Endocrine System Diseases / Q000097:blood* / Q000188:drug therapy*; D006801:Humans; D014807:Vitamin D / Q000494:pharmacology / Q000627:therapeutic use*
chemical_list: D001786:Blood Glucose; D014807:Vitamin D