In addition, mouse models unable to produce the active form of vitamin D, 1,25-dihydroxycholecalciferol [1,25(OH)2D3], or lacking the VDR are more susceptible to DSS-induced colitis and this is associated with intestinal dysbiosis characterized by an increase in species of the Proteobacteria phylum and a decrease in species of the Firmicutes phylum (163, 164). Here, VDR is linked to colitis.