Disease Localization and Bowel Resections as Predictors of Vitamin B12 and Vitamin D Status in Patients with Inflammatory Bowel Disease

Background: Terminal ileum inflammation and surgical resections impair absorption of vitamin B12 and D in patients with Crohn’s disease (CD) and Ulcerative Colitis (UC). We assessed differences in subclinical deficiencies of vitamin B12 (<350 pg/mL) or D (<50 nmol/L), by lesion localization (namely non-ileal CD, ileal CD, and UC) and surgical resection status (namely no resection, non-ileal small bowel resections, ileocecal resections, and colonic resections) in CD and UC patients. Methods: We analyzed data from 571 patients (17–93 years), with UC (51%) and CD (49%, including 47 non-ileal (8%), 244 ileal-CD (46%)) managed at the University of Missouri Health Care System (Jan 2017–April 2022). Results: Prevalence of vitamin B12 and vitamin D deficiencies was 19% and 83%, respectively. Prevalence of resection was 26%, including 5% with non-ileal small bowel resections, 11% with ileocecal resections, and 10% with colonic resections. CD with ileal involvement was associated with a 3-fold elevated risk of B12 deficiency (p = 0.004), but not vitamin D. Ileocecal resections were associated with a >3-fold increase in both B12 deficiency (OR = 3.53, p = 0.001) and D deficiency (OR = 3.35, p = 0.044). Conclusions: CD patients with ileal involvement and ileocecal resections have an elevated risk of vitamin B12 and D deficiency, and may benefit from adjunctive supplementation.