title: Lower serum 25 (OH) D concentrations in type 1 diabetes: A meta-analysis.
abstract: OBJECTIVE
  Vitamin D may have protective effects against type 1 diabetes (T1D). However, the results of current cross-sectional studies have been inconsistent. We aimed to examine the association of serum vitamin D and T1D by conducting a meta-analysis.
  
  
  METHODS
  Multiple databases were searched until April 2014 to identify relevant studies. The search term was "serum vitamin D" and "type 1 diabetes". Random effects model was used to calculate the pooled risk estimate. The data were accessed by software Review manager 5.2.
  
  
  RESULTS
  We included a total of 23 studies (11 studies with 1900 participants of children or adolescents and 13 studies with 3494 participants of adults) in our meta-analysis. In children or adolescents, serum 25(OH) D in T1D was 5.69 ng/ml [95% confidence interval (CI) (2.82-8.55, P<0.0001) lower than in healthy controls. In adults, serum 25(OH) D in T1D was 2.61 ng/ml [95% confidence interval (CI) (1.13-4.09, P=0.0005) lower than in healthy controls. We did not find evidence of publication bias.
  
  
  CONCLUSIONS
  Serum 25OHD is significantly lower in patients with T1D than in healthy controls.
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Harbin Medical University, Harbin, China; National Key Discipline, Harbin Medical University, Harbin, China.
authors.forename: Rennan
authors.initials: R
authors.lastname: Feng
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Harbin Medical University, Harbin, China; National Key Discipline, Harbin Medical University, Harbin, China.
authors.forename: Yanchuan
authors.initials: Y
authors.lastname: Li
authors.affiliation: Dean Office, Harbin Medical University, Harbin, China.
authors.forename: Guoqiang
authors.initials: G
authors.lastname: Li
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Harbin Medical University, Harbin, China; National Key Discipline, Harbin Medical University, Harbin, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Li
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Harbin Medical University, Harbin, China; National Key Discipline, Harbin Medical University, Harbin, China.
authors.forename: Yingfeng
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Endocrinology, Second Affiliated Hospital of Harbin Medical University, Harbin, China. Electronic address: liqiang_hmu@126.com.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Li
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Harbin Medical University, Harbin, China; National Key Discipline, Harbin Medical University, Harbin, China. Electronic address: changhao2002sun@gmail.com.
authors.forename: Changhao
authors.initials: C
authors.lastname: Sun
mesh_terms: D003922:Diabetes Mellitus, Type 1 / Q000097:blood* / Q000150:complications; D006801:Humans; D014807:Vitamin D / Q000097:blood*; D014808:Vitamin D Deficiency / Q000097:blood / Q000209:etiology*
chemical_list: D014807:Vitamin D
keywords: Meta-analysis; Serum vitamin D; Type 1 diabetes