Vitamin D as a predictor of severe course of inflammatory bowel diseases in children

Background. Inflammatory bowel diseases (IBD) develop in childhood more often, last throughout life, and their frequency is rapidly increasing in industrialized countries. Most researchers identify vitamin D (VD) as a key regulator of gastrointestinal homeostasis, an innate immune response and a biomarker for the activity and severity of IBD. The purpose was to determine the frequency of vitamin D deficiency and its relationship with the course of inflammatory bowel diseases in children. Materials and methods. The study included 36 patients: 13 with IBD (main group) and 23 children of the comparison group with irritable bowel syndrome and functional abdominal pain. The average age of children was 13.09 ± 2.28 years, with a median of 14.5 years; 63.6 % were boys. Patients with IBD were evaluated for clinical disease manifestations, disease localization (Paris Classification) and disease activity (PCDAI/PUCAI). Irritable bowel syndrome and functional abdominal pain were diagnosed based on the Rome IV Criteria. Serum 25-hydroxyvitamin D (25(OH)D) was assessed by the electrochemiluminescence method (Elecsys Vitamin D total, Cobas). Results. Severe IBD prevailed among the examined children (61.5  %). There was no significant difference in overall body weight and height between the groups, which may be due to the short duration of IBD. However, children with IBD showed a tendency to lower physical development indicators. Significant differences in hemoglobin, erythrocyte sedimentation rate, C-reactive protein, number of platelets, fecal calprotectin were observed among the studied groups (p < 0.05). The concentration of VD in the blood of the examined children ranged from 39.9 to 10.8 ng/ml, with an average of 21.8 ± 5.8 ng/ml. In 76.9 % of patients with IBD, blood concentration of VD reduced, while only 21.7 % children in the comparison group had its level below the norm. Children with IBD were characterized by significantly lower levels of VD in the blood (average of 16.7 ng/ml). Lower levels of VD were associated with female sex, Chron’s disease (CD) and ulcerative colitis (UC), as well as disease duration of more than 3 years and disease severity. There was an inverse correlation between VD and the degree of IBD activity (CD: r = –0.33; p = 0.01; UC: r = –0.38; p = 0.01) and the severity of the course (CD: r = –0.35; p = 0.01; UC: r = –0.36; p = 0.01), the levels of C-reactive protein (CD: r = –0.39; p = 0.01; UC: r = –0.37; p = 0.01) and fecal calprotectin (CD: r = –0.42; p = 0.01; UC: r = –0.46; p = 0.01). Conclusions. In most children (76.9 %) with inflammatory bowel diseases, the concentration of VD in the blood is significantly lower than in those with functional gastrointestinal disorders. Lower vitamin D levels were associated with female sex, Crohn’s disease, and ulcerative colitis, as well as disease duration of more than 3 years, activity level, and severity, supporting the role of vitamin D as a possible predictor of severity of these diseases in childhood.