Background Low levels of vitamin D have been widely reported in IBD with evidence suggesting a role in disease severity and treatment.

Aim Ireland has high rates of vitamin D deficiency both in IBD and general populations. Studies investigating correlation of vitamin D deficiency and disease parameters have been mixed.

Method We conducted a single centre retrospective study in our hospital from Jan 2015- June 2016. The aim was to assess the prevalence of vitamin D deficiency in IBD and non-IBD cohorts and to assess the impact of vitamin D deficiency on disease activity in IBD. Patients were separated into 4 groups: Crohns Disease (CD), Ulcerative Colitis (UC), general gastroenterology (GI) and general medical (non-GI). Basic demographic data disease specific information was recorded. Vitamin D deficiency was defined as <30 nmol/L.

Results 395 patients were studied: 157 CD, 70 UC, 75 GI and 93 non-GI. IBD patients were found to have high rates of Vitamin D deficiency (33% levels<30 nmol/L). Serum Vitamin D did not differ significantly between groups with mean values of 44.9 nmol/L (CD), 50.7 nmol/L(UC), 45.4 nmol/L(GI) and 45.6 nmol/L(non-GI). Symptommatic IBD patients had significantly higher mean CRP levels (8.6 mg/L) versus those who were asymptomatic (3.5 mg/L), (p<0.001). 35% of IBD patients who were symptomatic had vitamin D deficiency compared with 27% of those who were asymptomatic.

Conclusions We found very high rates of vitamin D deficiency in both IBD and non-IBD patients. Absolute levels did not differ significantly between groups. This may be accounted for by high overall prevalence of Vitamin D deficiency in this population or by confounders in the control population.