Objectives:
Magnesium is essential in numerous physiological processes, including the inflammatory response. However, its role in the pathogenesis and progression of juvenile idiopathic arthritis (JIA) remains underexplored. This study aimed to assess dietary magnesium intake and serum magnesium levels in children with JIA and to evaluate their potential impact on the clinical course of the disease.

Material and methods:
This case-control study included 42 children with JIA and 67 healthy controls aged 2 to 18 years. Juvenile idiopathic arthritis was diagnosed according to International League of Associations for Rheumatology criteria. Dietary magnesium intake was assessed in 26 JIA patients using a food frequency questionnaire, which collected information on the weekly consumption of foods rich in magnesium. The average weekly and daily magnesium intake was calculated and compared with national and international dietary recommendations. Serum magnesium levels were measured using the colorimetric method.

Results:
Children with JIA had significantly lower dietary magnesium intake (median: 227.71 mg/day vs. 261.18 mg/day, p = 0.040) and serum magnesium concentrations (mean: 0.79 mmol/l vs. 0.94 mmol/l, p = 0.009) than healthy controls. Insufficient dietary intake was more prevalent in the JIA group (50.0%) compared to controls (26.9%) (p < 0.034). Juvenile idiopathic arthritis patients with insufficient dietary magnesium intake were more likely to be male (p = 0.006), older than 12 years (p = 0.049), and residing in urban areas (p = 0.002). Hypomagnesemia was more common in boys (p = 0.030). However, neither low magnesium intake nor hypomagnesemia significantly influenced JIA disease activity.

Conclusions:
Children with JIA demonstrate significantly lower dietary and serum magnesium levels than their healthy peers. Larger pediatric studies are needed to clarify the potential contribution of magnesium to the development and clinical course of JIA.