Low Vitamin D and C Levels are Associated with Increased Disease Activity in Jordanian RA and SLE Patients: A Case-Control Study

Introduction: Rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) are chronic autoimmune diseases characterized by inflammation and tissue damage. Emerging evidence suggests vitamins D, C, and K may influence disease activity. The aim of this study is to assess serum vitamin levels in Jordanian RA and SLE patients and their association with disease activity. Methods: This case-control study included 156 participants recruited at the University of Jordan Hospital (January-September 2023): 99 patients with RA, 11 patients with SLE, and 46 healthy controls. Serum vitamin levels were measured by ELISA; inflammatory markers were extracted from medical records. Statistical analysis was performed using SPSS with significance set at P<0.05. Results and Discussion: RA and SLE patients showed significantly lower vitamin D (RA: 17.5 ±16.4 ng/ml, adjusted p=0.003; SLE: 13.7 ±8.3 ng/ml, adjusted p=0.044) and vitamin C (RA: 14.7 ± 5.3 mg/ml, adjusted p=0.003; SLE: 13.5 ± 3.5 ng/ml, adjusted p=0.003) levels versus controls (D: 33.3 ±20.9 ng/ml; C: 38.8 ±33.4 ng/ml). Vitamin K levels were reduced but remained within the reference range (RA: 2.2±1.1 ng/ml, adjusted p=0.003; SLE: 2.9±1.0 ng/ml, adjusted p=0.003). Deficiencies in vitamins D and C were found to be positively associated with elevated inflammatory markers, particularly ESR. No significant associations were found between vitamin levels and anti-CCP, ANA, joint involvement, or skin rash in RA and SLE patients; however, vitamin C levels were significantly associated with anti-CCP antibody expression in RA patients. Conclusion: In Jordanian RA and SLE patients, lower serum levels of vitamin D and C are associated with increased inflammation, underscoring the need for further research to explore the therapeutic potential of supplementation.