Dietary zinc intake, serum zinc concentrations, and disease activity in children with juvenile idiopathic arthritis: a case-control study.

INTRODUCTION: Zinc is an essential trace element involved in immune regulation and inflammatory responses. Children with juvenile idiopathic arthritis (JIA) may be at increased risk of nutritional deficiencies due to chronic inflammation, altered dietary intake, and long-term treatment. However, evidence regarding dietary zinc intake and serum zinc status in JIA remains inconsistent. This study aimed to evaluate dietary zinc intake and serum zinc concentrations in children with JIA and healthy controls and to explore their potential relationship with disease activity. METHODS: This unmatched case-control study included children with JIA and healthy controls aged 6-18 years. Dietary zinc intake was assessed using a semi-quantitative food frequency questionnaire. Serum zinc concentrations were measured using a colorimetric assay. Demographic, clinical, laboratory, dietary, and treatment characteristics were analyzed according to serum zinc status within the JIA cohort. RESULTS: Children with JIA had significantly lower dietary zinc intake than healthy controls (median 5.85 vs. 7.59 mg/day, p = 0.0019). Dietary intake was below the age- and sex-specific recommended level in 96.4% of children with JIA compared with 62.1% of controls (p < 0.0001). Mean serum zinc concentrations did not differ significantly between groups (p = 0.8872). Low serum zinc concentration (<11 μmol/L) was more frequent in children with JIA than controls (29.8% vs. 14.5%), although the difference was not statistically significant (OR 2.50, 95% CI 0.97-6.42; p = 0.0572). Within the JIA cohort, low serum zinc concentration was associated with higher erythrocyte sedimentation rate, patient and physician global assessment scores, and higher clinical JADAS-27 scores. However, overall JADAS-27 did not differ significantly between groups, and serum zinc concentration was not significantly correlated with JADAS-27 or clinical JADAS-27 when analyzed as a continuous variable. CONCLUSIONS: Children with JIA had substantially lower dietary zinc intake than healthy controls, whereas mean serum zinc concentrations did not differ significantly between the groups. Low serum zinc concentration was associated with selected measures of disease activity but did not show an independent or causal relationship with systemic inflammation. Prospective studies are needed to clarify the temporal relationships between dietary zinc intake, serum zinc status, inflammation, and disease activity and to determine whether nutritional interventions have clinically relevant effects.