Ulcerative colitis and Crohn's disease are two major forms of the inflammatory bowel diseases (IBDs). Vitamin A (VA) and vitamin D (VD) may be associated with reduction in inflammation in these disorders. The aim of this review was to show the current evidence that may associate VA and VD with IBDs. Data linking VA, VD, and IBDs were studied. Both VA and VD may be related to the immune system in different manners. The active form of VA, retinoic acid, may be related to the growth factor-β and release of interleukin-10 (IL-10), thus involved with the resolution of the inflammation. Its deficiency is associated with the increase of disease activity. The active form of VD is 1,25(OH)2D3 that produces biological effects via the nuclear hormone receptor named VD receptor (VDR), which may interfere with the immune cells and macrophages leading to the suppression of the inflammatory process by decreasing the release of TNF-α, IL-1, IL-6, and IL-8, IL-12, and IL-23. VDR may also activate nucleotide-binding oligomerization domain 2 expression and stimulate the production of the defensin and cathelicidin that are important to the homeostasis of the mucosal immune barrier. The use of VA and VD could be helpful in the treatment and prevention of IBDs but more studies are necessary to establish the precise role of these compounds in the prevention or remission of these inflammatory processes.
Keywords: Crohn's disease; inflammatory bowel disease; ulcerative colitis; vitamin A; vitamin D.