The Real-World Impact of Vitamin D Supplementation on Inflammatory Bowel Disease Clinical Outcomes.

Background and aims: Vitamin D deficiency is common in inflammatory bowel disease (IBD) and linked to adverse outcomes, yet the therapeutic role of vitamin D supplementation remains uncertain. We evaluated the real-world impact of vitamin D supplementation on corticosteroid use, emergency department (ED) visits, and hospitalizations in patients with IBD.

Methods: We conducted a retrospective cohort study of patients with IBD patients seen in the national Veterans Health Administration system from 2000 to 2023. All patients who had a vitamin D lab assay without a vitamin D prescription in the preceding three months were included. We used the quasi-experimental design with difference-in-differences analysis to compare vitamin D-treated and untreated groups before and after the 25-hydroxyvitamin D assay. Sensitivity analyses used regression discontinuity design (RDD) and inverse probability weighting (IPW) regression to confirm results from the primary analysis.

Results: Among 5,021 IBD patients (median age 63; 89% male; 58% ulcerative colitis, 39% Crohn's disease, 3% indeterminate colitis), the median 25-hydroxyvitamin D level was 23 ng/mL, and 41% received vitamin D supplementation. Vitamin D supplementation was associated with reduction in IBD-related ED visits by 2.17% (34.4% RRR, p=0.007), hospitalizations by 2.64% (53.18% relative risk reduction (RRR), p=0.003), and corticosteroid prescriptions by 1.29% (25.13% RRR, p=0.066). Similar results were seen in the inverse probability weighted regression and RDD analyses.

Conclusion: Vitamin D supplementation was associated with reduced IBD-related ED visits, hospitalizations, and corticosteroid use, supporting its potential as a low-cost adjunct in IBD management. Prospective studies are needed to optimize dosing strategies and define target serum levels for improved long-term outcomes.