Vitamin D deficiency in Crohn's disease and healthy controls: A prospective case-control study in the Netherlands

Background and aims: Vitamin D deficiency has been observed in a wide range of medical conditions including Crohn's disease (CD). We aimed to assess whether CD patients have lower vitamin D levels than healthy controls, and to determine risk factors for vitamin D deficiency. Methods: 25(OH)D was measured by chemiluminescent immunoassay in serum obtained from 101 CD patients and 41 controls. Demographics, sunlight exposure, dietary vitamin D intake, comorbidities and medication were recorded using validated questionnaires. In CD patients the Harvey-Bradshaw index, Montreal classification and surgical resections were also evaluated. 25(OH)D levels of >75 nmol/L, between 50 and 75 nmol/L and <50 nmol/L were considered as normal, suboptimal and deficient, respectively. Results: Vitamin D levels were rather low but comparable among CD patients and controls (mean 25(OH)D 51.6 nmol/L(+/-26.6) in CD, and 60.8 nmol/L(+/-27.6) in controls. Multivariate regression analysis revealed BMI, sun protection behaviour, non-Caucasian ethnicity, no use of tanning beds, and no holidays in the last year as significantly associated with serum 25(OH)D levels in CD patients (R = 0.62). In the control group no statistically significant factors were identified that had an impact on 25(OH)D serum levels. Conclusions: Vitamin D deficiency is common in CD patients, but also in healthy controls. Appropriate vitamin D screening should be advised in patients with CD. Moreover, the positive effect of sunlight on the vitamin D status should be discussed with CD patients, but this should be balanced against the potential risk of developing melanomas, especially in patients using thiopurines. (C) 2014 European Crohn's and Colitis Organisation. Published by Elsevier B.V. All rights reserved.