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

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 visits, and hospitalizations in patients with IBD.

We conducted a retrospective cohort study of patients with IBD seen in the national Veterans Health Administration system from 2000 to 2023. All patients who had a vitamin D laboratory assay without a vitamin D prescription in the preceding 3 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 and inverse probability weighting regression to confirm results from the primary analysis.

Among 5021 patients with IBD (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 emergency department visits by 2.17% (34.4% relative risk reduction; P = .007), hospitalizations by 2.64% (53.18% relative risk reduction; P = .003), and corticosteroid prescriptions by 1.29% (25.13% relative risk reduction; P = .066). Similar results were seen in the inverse probability weighted regression and regression discontinuity design analyses.

Vitamin D supplementation was associated with reduced IBD-related emergency department 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.