title: Effect of vitamin D supplementation on insulin resistance and glycaemic control in prediabetes: a systematic review and meta-analysis.
abstract: OBJECTIVE
  To evaluate the effect of vitamin D on insulin resistance and glycaemic control in prediabetes.
  
  
  METHODS
  A literature search was conducted of MEDLINE, the Cochrane Library, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Scopus, Web of Science and www.clinicaltrials.gov, together with a historical search through the reference lists of relevant articles until end of June 2014. Studies were included if they were randomized controlled trials of vitamin D or vitamin D analogues in prediabetes and if they reported homeostatic model assessment of insulin resistance or 2-h plasma glucose after oral glucose tolerance test. Treatment effect was estimated according to mean difference in the changes from baseline of homeostatic model assessment of insulin resistance, 2-h oral glucose tolerance test plasma glucose, fasting plasma glucose and HbA1c between vitamin D and control groups. Meta-analysis of eligible studies was performed.
  
  
  RESULTS
  A total of 10 randomized controlled trials were included. Vitamin D did not significantly improve homeostatic model assessment of insulin resistance and 2-h oral glucose tolerance test plasma glucose: the mean differences were -0.06 (95% CI -0.36 to 0.24) and -0.23 mmol/l (95% CI -0.65 to 0.19), respectively. Subgroup analysis suggested that vitamin D improved homeostatic model assessment of insulin resistance in a subgroup with baseline 25-hydroxyvitamin D ≥ 50 nmol/l [mean difference -0.59 (95% CI -1.14 to -0.04); P = 0.03] and improved 2-h oral glucose tolerance test plasma glucose in the subgroup with baseline 25-hydroxyvitamin D < 50 nmol/l [mean difference -0.68 mmol/l (95% CI -1.35 to -0.01); P = 0.05]. Vitamin D significantly reduced fasting plasma glucose and HbA1c levels. The mean differences were -0.10 mmol/l (95% CI -0.18 to -0.03), P = 0.006 and -1 mmol/mol (95% CI -2 to 0), P = 0.008, respectively.
  
  
  CONCLUSIONS
  No beneficial effect of vitamin D in improving insulin resistance was identified.
authors: Department of Pharmacy, Faculty of Pharmacy, Silpakorn University, Nakhon-Pathom, Thailand.
authors: N
authors: N
authors: Poolsup
authors: Department of Pharmacy, Faculty of Pharmacy, Mahidol University, Bangkok, Thailand.
authors: N
authors: N
authors: Suksomboon
authors: Department of Pharmacy, Faculty of Pharmacy, Mahidol University, Bangkok, Thailand.
authors: N
authors: N
authors: Plordplong
mesh_terms: D001786:Blood Glucose / Q000187:drug effects* / Q000378:metabolism; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000150:complications / Q000517:prevention & control; D019587:Dietary Supplements; D006801:Humans; D007333:Insulin Resistance; D044623:Nutrition Therapy; D011236:Prediabetic State / Q000097:blood / Q000178:diet therapy* / Q000378:metabolism*; D014807:Vitamin D / Q000008:administration & dosage*; D014808:Vitamin D Deficiency / Q000097:blood / Q000150:complications / Q000178:diet therapy
chemical_list: D001786:Blood Glucose; D014807:Vitamin D