The role of vitamin D in gastrointestinal inflammation

Abstract

The emerging role of vitamin D as a regulator of both innate and adaptive immune responses has encouraged the investigation of its role in the pathogenesis of a variety of autoimmune conditions including the inflammatory bowel diseases (IBD), Crohn’s disease and ulcerative colitis. Animal models consistently demonstrate that vitamin D significantly impacts on the modulation of astrointestinal inflammation, while epidemiological and observational data show an inverse relationship between vitamin D status and the onset/progression of Crohn’s disease as well as the development of colorectal cancer. As vitamin D supplementation is readily available, at low cost, it is a very attractive potential therapeutic option. The biological plausibility for a role for vitamin D in inflammation modulation, the potential genetic links associated with vitamin D metabolism and the clinical aspects for it in IBD will be discussed.

Keywords::

• immunoregulation
• inflammation
• inflammatory bowel disease
• treatment
• vitamin D

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending or royalties.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Vitamin D deficiency is common in both Crohn’s disease and ulcerative colitis with a prevalence of approximately 30%.

• Epidemiological data show an increased risk of developing inflammatory bowel diseases (IBD) in areas of low UV exposure, several lines of evidence suggest this is due to vitamin D deficiency, but there is emerging evidence that UV radiation may have a role in systemic immunosuppression independent of vitamin D.

• Vitamin D deficiency is associated with more active disease and worse outcomes such as hospitalization and surgery. Preliminary data suggest that vitamin D replacement may lead to better outcomes and maintain remission in Crohn’s disease. Further studies are needed to verify this.

• Vitamin D deficiency is associated with reduced muscle bulk in IBD and may play a role in maintaining balance and falls prevention.

• Multiple lines of evidence link vitamin D with the pathogenesis of IBD. Several genetic loci implicated in the development of IBD, such as nucleotide-binding oligomerization domain-containing protein 2, are dependent on vitamin D for normal expression, particular vitamin D receptor variants may be more frequent in IBD populations and vitamin D-binding properties due to genetic variants in IBD may also be altered. Altered gastrointestinal barrier, innate and adaptive immune function in vitamin D deficiency may contribute to IBD pathogenesis.