Mendelian randomization refers to a type of epidemiological study that incorporates genetic information. About a year ago I wrote a about how they work using as an example of a study on obesity and vitamin D that Dr. Cannell had previously reported on.
In that study, the researchers looked at simple mutations, called single nucleotide polymorphisms (SNPs). SNPs related to higher BMI were also related to lower vitamin D status, but SNPS related to overall vitamin D status were not related to overall BMI. This suggests that obesity causes low vitamin D rather than low vitamin D causing obesity.
Today we’ll look at a new Mendelian randomization study from The Lancet that looked at the relationship between vitamin D SNPs and type 2 diabetes: