Abstract and Introduction
Background Vitamin D is traditionally associated with bone metabolism. The immunological effects of vitamin D have increasingly come into focus.
Aim To review the evidence supporting a role of vitamin D in inflammatory bowel diseases.
Methods A comprehensive search was performed on PubMed using the terms 'crohn's disease' 'ulcerative colitis' and 'vitamin D'.
Results Vitamin D deficiency is common in patients with inflammatory bowel diseases (IBD) (16–95%) including those with recently diagnosed disease. Evidence supports immunological role of vitamin D in IBD. In animal models, deficiency of vitamin D increases susceptibility to dextran sodium sulphate colitis, while 1,25(OH)2D3 ameliorates such colitis. One prospective cohort study found low predicted vitamin D levels to be associated with an increased risk of Crohn's disease (CD). Limited data also suggest an association between low vitamin D levels and increased disease activity, particularly in CD. In a large cohort, vitamin D deficiency (<20 ng/mL) was associated with increased risk of surgery (OR 1.8, 95% CI 1.2–2.5) in CD and hospitalisations in both CD (OR 2.1, 95% CI 1.6–2.7) and UC (OR 2.3, 95% CI 1.7–3.1). A single randomised controlled trial demonstrated that vitamin D supplementation may be associated with reduced frequency of relapses in patients with CD compared with placebo (13% vs. 29%, P = 0.06).
Conclusions There is growing epidemiological evidence to suggest a role for vitamin D deficiency in the development of IBD and also its influence on disease severity. The possible therapeutic role of vitamin D in patients with IBD merits continued investigation.
Ulcerative colitis (UC) and Crohn's disease (CD) constitute chronic idiopathic inflammatory bowel diseases (IBD). The key underlying pathogenic mechanisms for both diseases is a dysregulated host immune response to commensal intestinal flora in genetically susceptible individuals.[1,2] Known genetic variants incompletely explain the variance in disease incidence, suggesting a strong role for environmental factors, supported by epidemiological evidence.[3,4]
Vitamin D has long been recognised as a major regulator of calcium and phosphorus metabolism and key in maintaining bone health.[5–7] However, several recent studies have yielded new insights into the role of vitamin D in various other physiological processes. In particular, vitamin D appears to play important roles in immune regulation, particularly involving the innate immune system, cardiovascular and renal physiology, and development of cancer. Importantly, an increasing body of literature supports an important role of vitamin D in the pathogenesis as well as potential therapy of IBD.[8–13] The current review examines the evidence linking vitamin D to IBD, both through its effect on bone health and association with pathogenesis and natural history of these diseases.
Aliment Pharmacol Ther. 2014;39(2):125-136. © 2014 Blackwell Publishing