VITAMIN STATUS D AND INTAKE IN CHILDREN WITH JUVENILE IDIOPATHIC ARTHRITIS

Abstract

Recent research has increasingly focused on the role of vitamin D in the pathogenesis of autoimmune and inflammatory diseases. Aim of the study. To assess dietary vitamin D intake and serum 25-hydroxyvitamin D [25(OH)D] levels in children with juvenile idiopathic arthritis (JIA) and to determine the association between vitamin D status and clinical characteristics and disease activity. Materials and methods. A prospective controlled study enrolled children aged 5–17 years. The study group included 57 patients with JIA diagnosed using International League of Associations for Rheumatology (ILAR) criteria. The control group consisted of 67 apparently healthy, age-matched children. Clinical examinations and structured questionnaires were administered to the study cohort to collect demographic data (age, sex, place of residence), lifestyle characteristics, dietary habits, and vitamin D supplement use. In the JIA cohort, additional assessments included disease duration, JIA subtype, disease activity, extra-articular manifestations, immunological markers (ANA, HLA-B27), laboratory parameters, and treatment regimens (methotrexate, glucocorticoids, and biologic therapies). Dietary vitamin D intake was quantified using a questionnaire assessing the frequency and portion sizes of vitamin D-rich foods consumed. These data were utilized to calculate the mean daily vitamin D intake, which was subsequently compared against age-specific recommendations. Serum 25(OH)D concentrations were determined via enzyme-linked immunosorbent assay (ELISA) using Monobind Microwell ELISA kits (USA). Blood samples were collected during the autumn–winter period to minimize the effect of sunlight exposure. Vitamin D status was classified according to current clinical guidelines as follows: deficiency (<20 ng/mL), insufficiency (20–<30 ng/mL), and sufficiency (30–50 ng/mL). Disease activity was assessed using the Juvenile Arthritis Disease Activity Score (JADAS-27). Written informed consent was obtained from the parents or legal guardians of all participants, with the study protocol adhering to the Declaration of Helsinki and receiving approval from the Bioethics Committee of I. Horbachevsky Ternopil National Medical University (Protocol No. 60, September 1, 2020). Statistical analysis was conducted using STATISTICA 10.0 and Microsoft Excel. Normally distributed quantitative variables were presented as mean ± standard deviation (SD), while non-normally distributed data were expressed as median and interquartile range (IQR). Between-group comparisons were performed using the Student t-test, Mann–Whitney U test, one-way analysis of variance (ANOVA), Pearson χ² test, and Fisher–Freeman–Halton exact test. Differences were considered statistically significant at P < 0.05. The study was conducted as part of the project “Characteristics of Vitamin and Mineral Status in Healthy Children and Children with Socially Significant Diseases” (state registration no. 0121U100069; research period: 2021–2022), funded by the Ministry of Health using state budget funds, and the project “Improving Methods for the Diagnosis, Treatment, and Prevention of Socially Significant Diseases in Children” (project no. 0125U000113; research period: 2025–2027). Results. The mean age of the children with JIA was 12.1 ± 3.6 years, with a mean disease duration of 3.7 ± 2.9 years. Oligoarthritis was the most prevalent clinical subtype (47.4%), with active disease observed in 49.1% of patients. Median daily vitamin D intake in children with JIA was 144.6 IU [63.05–227.40], significantly lower than in healthy children (203.56 IU [80.29–389.06]; P = 0.0162). Inadequate dietary vitamin D intake was identified in 96.4% of patients. Serum 25(OH)D levels were assessed in 53 children with JIA and 67 healthy controls. Vitamin D deficiency, insufficiency, and sufficiency were observed in 47.2%, 33.9%, and 18.9% of children with JIA, respectively. Mean serum 25(OH)D concentration in the JIA group was 22.88 ± 9.75 ng/mL and did not differ significantly from that in the control group (20.65 ± 8.07 ng/mL, P = 0.1607). No significant association was observed between vitamin D status and sex, age, disease duration, JIA subtype, ANA positivity, HLA-B27 status, uveitis, disease activity, or treatment regimens (P > 0.05). Although not statistically significant, patients with vitamin D deficiency exhibited a trend toward higher disease activity based on JADAS-27 scores (5.23 ± 5.16 vs. 3.40 ± 3.78 in patients with normal vitamin D status; P = 0.129). Children receiving vitamin D supplementation demonstrated higher serum 25(OH)D concentrations than unsupplemented patients (25.03 ± 7.97 ng/mL vs. 20.50 ± 7.16 ng/mL, P = 0.0415). Conclusions. Children with JIA exhibited a high prevalence of inadequate dietary vitamin D intake and suboptimal serum 25(OH)D status, with deficiency or insufficiency identified in 81.1% of patients. Vitamin D status in children with JIA did not differ significantly from that in healthy controls, likely reflecting the high prevalence of hypovitaminosis D in the general pediatric population alongside more frequent supplementation among patients with JIA. Vitamin D supplementation was associated with higher serum 25(OH)D concentrations. These findings underscore the importance of monitoring vitamin D status and ensuring timely correction of deficiency as an integral component of comprehensive clinical management in children with JIA.