Association between inflammatory bowel disease and Vitamin D deficiency: A systematic review and meta-analysis

Background: Vitamin D plays a role in several immune-mediated diseases, but its association with inflammatory bowel disease (IBD) is unclear. We conducted a systematic review and meta-analysis to assess the association between IBD and Vitamin D deficiency. Methods: We searched electronic databases from inception to December 2014 for observational studies reporting the presence of Vitamin D deficiency (defined as serum 25-hydroxycholecalciferol [25(OH)D] level of ≤20 ng/mL) in IBD patients and having a control group without IBD. Odds ratios (ORs) were combined using a random-effects model. Meta-regression was performed using latitude as a moderator. Study quality was assessed using the Newcastle-Ottawa scale. Results: Out of 816 citations, 14 eligible studies were identified, comprising 1891 participants (938 IBD cases and 953 controls). Meta-analysis showed that patients with IBD had 64% higher odds of Vitamin D deficiency when compared with controls (OR 1.64; 95% confidence interval, 1.30-2.08; I 2 7%; P < 0.0001). Patients with ulcerative colitis had more than double the odds of Vitamin D deficiency when compared with normal controls (OR 2.28; 95% confidence interval, 1.18-4.41; I 2 41%; P 0.01). Latitude did not influence the association between IBD and Vitamin D deficiency (P 0.34). Generalizability of our results might be limited as we summarized unadjusted ORs, because of nonavailability of adjusted ORs in individual studies. Conclusions: IBD is significantly associated with having higher odds of Vitamin D deficiency. Well-designed randomized controlled trials and longitudinal studies are needed to further explain the role of Vitamin D in IBD pathogenesis and its therapy.