The Effect of Quercetin on Inflammatory Factors and Clinical Symptoms in Women with Rheumatoid Arthritis: A Double-Blind, Randomized Controlled Trial

Objective: Previous studies have shown that the bioflavonoid quercetin has anti-inflammatory and anti-nociceptive effects. We investigated the effect of quercetin supplementation on inflammation, disease severity, and clinical symptoms in women with rheumatoid arthritis (RA). Methods: The present study was a randomized, double-blind, placebo-controlled clinical trial in which 50 women with RA were allocated into a quercetin (500 mg/day) or placebo group for 8 weeks. Plasma levels of high-sensitivity tumor necrosis factor-alpha (hs-TNF alpha), erythrocyte sedimentation rate (ESR), clinical symptoms including early morning stiffness (EMS), morning and after-activity pain, and tender (TSC) and swollen joint counts (SJC) were determined. Disease activity and functional disability were assessed by Disease Activity Score 28 (DAS-28), physician global assessment (PGA), and a health assessment questionnaire (HAQ) at the beginning and end of the study. Results: Quercetin supplementation for 8 weeks significantly reduced EMS, morning pain, and after-activity pain (p < 0.05). DAS-28 and HAQ scores decreased in the quercetin group compared to placebo and the number of patients with active disease significantly decreased in the quercetin group. Plasma hs-TNF alpha level was significantly reduced in the quercetin group compared to placebo (p < 0.05). There were no significant differences in TJC and SJC between groups but TJC significantly decreased in the quercetin group after the intervention. Supplementation had an effect on ESR but it was not significant (p > 0.05). Conclusions: Five hundred milligrams per day quercetin supplementation for 8 weeks resulted in significant improvements in clinical symptoms, disease activity, hs-TNF alpha, and HAQ in women with RA.