AIM: To investigate the effect of vitamin D(VD) concentrations and VD supplementation on health related quality of life in inflammatory bowel disease(IBD) patients. METHODS: A cohort of 220 IBD patients including 141 Crohn’s disease(CD) and 79 ulcerative colitis(UC) patients was followed-up at a tertiary IBD center. A subgroup of the cohort(n = 26) took VD supplements for > 3 mo. Health related quality of life was assessed using the short IBD questionnaire(s IBDQ). VD serum concentration and s IBDQ score were assessed between August and October 2012(summer/autumn period) and between February and April 2013(winter/spring period). The mean VD serum concentration and its correlation with disease activity of CD were determined for each season separately. In a subgroup of patients, the effects of VD supplementation on winter VD serum concentration, change in VD serum concentration from summer to winter, and winter s IBDQ score were analyzed.RESULTS: During the summer/autumn and the winter/spring period, 28% and 42% of IBD patients were VD-deficient(< 20 ng/m L), respectively. In the winter/spring period, there was a significant correlation between s IBDQ score and VD serum concentration in UC patients(r = 0.35, P = 0.02), with a trend towards significance in CD patients(r = 0.17, P = 0.06). In the winter/spring period, VD-insufficient patients(< 30 ng/m L) had a significantly lower mean s IBDQ score than VD-sufficient patients; this was true of both UC(48.3 ± 2.3 vs 56.7 ± 3.4, P = 0.04) and CD(55.7 ± 1.25 vs 60.8 ± 2.14, P = 0.04) patients. In all analyzed scenarios(UC/CD, the summer/autumn period and the winter/spring period), health related quality of life was the highest in patients with VD serum concentrations of 50-59 ng/m L. Supplementation with a median of 800 IU/d VD day did not influence VD serum concentration or the s IBDQ score.CONCLUSION: VD serum concentration correlated with health related quality of life in UC and CD patients during the winter/spring period. AIM: To investigate the effect of vitamin D (VD) concentrations and VD supplementation on health related qualities of life in inflammatory bowel disease (IBD) patients. METHODS: A cohort of 220 IBD patients including 141 Crohn’s disease (CD) and 79 ulcerative colitis A subgroup of the cohort (n = 26) took VD supplements for> 3 mo. Health related quality of life was assessed using the short IBD questionnaire (s IBDQ). VD serum mean and s IBDQ score were assessed between August and October 2012 (summer / autumn period) and between February and April 2013 (winter / spring period). The mean VD serum concentration and its correlation with disease activity of CD were determined for each season In a subgroup of patients, the effects of VD supplementation on winter VD serum concentration, change in VD serum concentration from summer to winter, and winter s IBDQ score were measured .RESULTS: During the summer / autumn and the winter / s In the winter / spring period, there was a significant correlation between s IBDQ score and VD serum concentration in UC patients (<20 ng / m L) with a trend towards significance in CD patients (r = 0.17, P = 0.06). In the winter / spring period, VD-limited patients (<30 ng / m L) had a significantly lower mean s IBDQ score than VD-sufficient patients; this was true of both UC (48.3 ± 2.3 vs 56.7 ± 3.4, P = 0.04) and CD (55.7 ± 1.25 vs 60.8 ± 2.14, P = 0.04) (UC / CD, the summer / autumn period and the winter / spring period), health related quality of life was the highest in patients with VD serum concentrations of 50-59 ng / m L. Supplementation with a median of 800 IU / d VD day did not affect VD serum concentration or the s IBDQ score. CONCLUSION: VD serum concentration correlated with health related quality of life in UC and CD patients during the winter / spring period.