Vitamin D supplement in early childhood and risk for Type I (insulin-dependent) diabetes mellitus

The initiation of the immunopathogenetic process that can lead to Type I (i nsulin-dependent) diabetes mellitus in childhood probably occurs early in l ife. Studies in vitro have shown that vitamin D3 is immunosuppressive or im munomodulating and studies in experimental models of autoimmunity, includin g one for autoimmune diabetes, have shown vitamin D to be protective. Seven centres in Europe with access to population-based and validated case regis ters of insulin-dependent diabetes patients participated in a case-control study focusing on early exposures and risk of Type I diabetes. Altogether d ata from 820 patients and 2335 control subjects corresponding to 85% of eli gible patients and 76% of eligible control subjects were analysed. Question s focused on perinatal events and early eating habits including vitamin D s upplementation. The frequency of vitamin D supplementation in different cou ntries varied from 47 to 97% among control subjects. Vitamin D supplementat ion was associated with a decreased risk of Type I diabetes without indicat ion of heterogeneity. The Mantel-Haenszel combined odds ratio was 0.67 (95% confidence limits: 0.53, 0.86). Adjustment for the possible confounders: a low birth weight, a short duration of breast feeding, old maternal age and study centre in logistic regression analysis did not affect the significan t protective effect of vitamin D. In conclusion, this large multicentre tri al covering many different European settings consistently showed a protecti ve effect of vitamin D supplementation in infancy. The findings indicate th at activated vitamin D might contribute to immune modulation and thereby pr otect or arrest an ongoing immune process initiated in susceptible people b y early environmental exposures.