Type 1 diabetes risk unaffected by vitamin D levels: Study

Canada: Vitamin D levels are not likely to have large effect on type 1 diabetes risk (T1D), suggests a recent study in the journal PLOS Medicine. However, the researchers added that larger MR studies or RCTs are required to investigate small effects.

"Our findings suggest that vitamin D levels are unlikely to have a large effect on risk of type 1 diabetes," wrote the authors. 

In observational studies, vitamin D deficiency is shown to be associated with T1D but there is a lack of evidence from randomized controlled trials (RCTs). Despoina Manousaki, Research Center of the Sainte-Justine University Hospital, Montreal, Quebec, Canada, and colleagues aimed to test whether genetically decreased vitamin D levels are causally associated with type 1 diabetes using Mendelian randomization (MR).

For the two-sample MR study, the researchers selected as instruments single nucleotide polymorphisms (SNPs) that are strongly associated with 25-hydroxyvitamin D (25OHD) levels in a large vitamin D genome-wide association study (GWAS). It included 443,734 Europeans and obtained their corresponding effect estimates on type 1 diabetes risk from a large meta-analysis of 12 type 1 diabetes GWAS studies (Ntot = 24,063, 9,358 cases, and 15,705 controls).