In contrast to observational findings, no clear association has been reported between genetically predicted coffee consumption and type 2 diabetes in mendelian randomisation analyses.3 32 33 A one sample mendelian randomisation analysis based on the Copenhagen General Population Study showed no association of a allele score for coffee intake, consisting of SNPs near CYP1A2 and AHR genes, with risk of type 2 diabetes.32 The gene discussed is AHR; the disease is type 2 diabetes mellitus.