Effects of quercetin on oxidative and inflammatory markers and disease activity of rheumatoid arthritis patients

INTRODUCTION: Quercetin is a flavonoid which has showed anti-oxidative, anti-inflammatory and anti-hypertensive properties in many studies. OBJECTIVES: The aim was to determine the effects of quercetin on plasma total antioxidant capacity (TAC), lipid-peroxidation, blood pressure, inflammatory factors, disease activity and clinical outcomes in patients with Rheumatoid Arthritis. METHOD / DESIGN: The present study was a randomized, placebo-control and double-blind clinical trial, in which 51 patients with RA, aged 19-70 years, were recruited. Patients were randomly assigned to two groups and received either quercetin (500 mg/d) or placebo capsules for 8 weeks. Fasting blood samples were taken at the baseline and the end of the study. TAC , MDA, ox-LDL, hs-CRP, hs-TNFα , ESR and RF were measured. Blood pressure, morning stiffness and pain, night pain, after activity pain , swelling joint count (SJC), tender joint count (TJC), disease activity score (DAS-28) and PGA were assessed at baseline and after intervention. RESULTS: Quercetin had no significant effect on TAC, MDA, ox-LDL, hs-CRP, hs-TNFα, ESR, RF and blood pressure. Morning stiffness was significantly less in the quercetin group compared to placebo (P=0.03). Morning and night pain was significantly less in quercetin group compared to placebo (P=0.005 and P=0.01, respectively). Pain after physical activity and morning pain significantly decreased in quercetin group after intervention (P=0.001 and P=0.004, respectively). In quercetin group mean daily intake of NSAIDs and acetaminophen were less than placebo group (P=0.01). Quercetin decreased significantly TJC and DAS-28 (P=0.04 and P=0.001, respectively). CONCLUSIONS: Although quercetin supplementation for 8 weeks had no effect on blood pressure, oxidative and inflammatory biomarkers, but it could improve or alleviate clinical outcomes such as pain, morning stiffness and disease activity score in patients with RA.