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

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Background and aimsVitamin 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. Methods25(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 >75nmol/L, between 50 and 75nmol/L and <50nmol/L were considered as normal, suboptimal and deficient, respectively. ResultsVitamin D levels were rather low but comparable among CD patients and controls (mean 25(OH)D 51.6nmol/L(±26.6) in CD, and 60.8nmol/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. ConclusionsVitamin 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.