title: Vitamin D intake and risk of type 1 diabetes: a meta-analysis of observational studies.
abstract: Vitamin D is suggested to have protective effects against type 1 diabetes. However, the results from observational studies have been inconsistent. We aimed to examine their association by conducting a meta-analysis of observational studies. Multiple databases were searched in June 2013 to identify relevant studies including both case-control and cohort studies. Either a fixed- or random-effects model was used to calculate the pooled risk estimate. We identified eight studies (two cohort studies and six case-control studies) on vitamin D intake during early life and three studies (two cohort studies and one case-control study) on maternal vitamin D intake during pregnancy. The pooled odds ratio for type 1 diabetes comparing vitamin D supplementation with non-supplementation during early life was 0.71 (95% confidence interval [CI], 0.51-0.98). Similar results were observed in the case-control subgroup analysis but not in the cohort subgroup analysis. The pooled odds ratio with maternal intake of vitamin D during pregnancy was 0.95 (95% CI, 0.66-1.36). In conclusion, vitamin D intake during early life may be associated with a reduced risk of type 1 diabetes. However, there was not enough evidence for an association between maternal intake of vitamin D and risk of type 1 diabetes in the offspring.
authors.affiliation: Department of Nutrition and Food Hygiene, School of Public Health, Soochow University, 199 Renai Road, Suzhou 215123, China. qinliqiang@suda.edu.cn.
authors.forename: Jia-Yi
authors.initials: JY
authors.lastname: Dong
authors.forename: Wei-Guo
authors.initials: WG
authors.lastname: Zhang
authors.forename: Jiong Jack
authors.initials: JJ
authors.lastname: Chen
authors.forename: Zeng-Li
authors.initials: ZL
authors.lastname: Zhang
authors.forename: Shu-Fen
authors.initials: SF
authors.lastname: Han
authors.forename: Li-Qiang
authors.initials: LQ
authors.lastname: Qin
mesh_terms: D016208:Databases, Factual; D003922:Diabetes Mellitus, Type 1 / Q000517:prevention & control*; D019587:Dietary Supplements; D006801:Humans; D064887:Observational Studies as Topic; D016017:Odds Ratio; D012307:Risk Factors; D014807:Vitamin D / Q000008:administration & dosage* / Q000097:blood; D014815:Vitamins / Q000008:administration & dosage* / Q000097:blood
chemical_list: D014815:Vitamins; D014807:Vitamin D
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