Vitamin D deficiency in adult patients with ulcerative colitis: Prevalence and relationship with disease severity, extent, and duration.

Background: Vitamin D plays a key role in gut immunity and maintenance of the mucosal barrier. Vitamin D deficiency (VDD) worsens ulcerative colitis (UC) and its supplementation ameliorates the disease in mouse models. The prevalence and predictors of VDD in UC are not known.
Methods: Consecutive patients with UC (n = 80) underwent clinical, endoscopic, and histological evaluation to assess the extent, severity using UC disease activity index (UCDAI) score, and duration of illness. An equal number of age and gender-matched healthy adults without any features of inflammatory bowel disease (IBD) living in the same latitude were identified as controls. The serum 25-hydroxy vitamin D ₃ level was estimated. The subjects were classified as deficient (< 20 ng/mL), insufficient (20-32 ng/mL), sufficient (32-80 ng/mL), and optimal (> 80 ng/mL) based on vitamin D levels. Chi-square test and Mann-Whitney U test were done to identify factors associated with vitamin D deficiency.
Results: The patients and controls were similar in age and gender (40 ± 11.4 years, 51% male vs. 40 ± 12 years, 51% male; p = 1.000). Median vitamin D levels among patients were lower than the controls (18.1 ng/mL [IQR 14] vs. 32.5 ng/mL [IQR 36]; p < 0.001). Patients were more often VDD (56% vs. 40%) or insufficient (34% vs. 9%) and less often sufficient (9% vs. 40%) or optimal (1% vs. 11%), in contrast to controls (p < 0.001). Median vitamin D levels were lower in those with UCDAI > 6 (15 vs. 21 ng/mL; p = 0.01), having pancolitis (13 vs. 21 ng/mL, p = 0.01), and longer duration of illness > 2 years (13.8 vs. 20.8; p = 0.025). Vitamin D levels showed a negative correlation with frequency of stools (rho = - 0.244, p = 0.05), disease duration (rho = - 0.244, p = 0.007) and UCDAI score (r = - 0.348, p = 0.002).
Conclusion: VDD is highly prevalent among patients with UC. Patients with longer disease duration, more severe symptoms, and pancolitis are likely to have lower vitamin D levels.