Quercetin

Quercetin in COVID-19 Treatment (Early-Stage Patients)

Study: A single-center, open-label, randomized controlled clinical trial conducted at King Edward University, Lahore, Pakistan, evaluated quercetin (500 mg Quercetin Phytosome®) as an add-on to standard care in 100 outpatients with mild to moderate COVID-19. Patients received 500 mg thrice daily for the first week, then twice daily for the second week. The study assessed virus clearance, symptom resolution, and inflammatory biomarkers.

Findings: Quercetin supplementation significantly reduced the time to SARS-CoV-2 clearance (via RT-PCR), led to earlier resolution of acute symptoms, and improved serum inflammatory biomarker levels (e.g., LDH, ferritin) compared to standard care alone. It also reduced hospitalization rates, need for non-invasive oxygen therapy, ICU admission, and mortality.

Link: https://www.frontiersin.org/articles/10.3389/fphar.2022.898205/full

Quercetin in COVID-19 (Second Pilot Study)

Study: A 2-week, open-label, randomized controlled trial enrolled 42 outpatients with mild COVID-19, comparing standard care (SC) to SC plus Quercetin Phytosome® (1500 mg/day for week 1, 1000 mg/day for week 2). The study aimed to assess virus clearance and symptom improvement.

Findings: After one week, 16 patients in the quercetin group tested negative for SARS-CoV-2, and 12 had diminished symptoms, compared to only 2 testing negative and 4 with partial symptom improvement in the SC group. Quercetin improved virus clearance, symptom frequency, and biomarkers (LDH, ferritin).

Link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8226892/

Quercetin for Chronic Fatigue Symptoms

Study: A randomized, double-blind, placebo-controlled trial evaluated 500 mg Quercetin Phytosome™ daily for 2 months in 78 subjects (42 female, 36 male, mean age 56) with chronic fatigue symptoms. The primary endpoint was the Fatigue Impact Scale (FIS-40).

Findings: Quercetin supplementation significantly reduced fatigue (FIS-40 mean difference: -10.583 points, p<0.001), improved sleep quality (Pittsburgh Sleep Quality Index: -2.040 points, p<0.01), increased step count (1443.152 steps, p<0.001), and improved physical performance (SPPB score: 0.248, p<0.001) compared to placebo.

Link: https://www.sciencedirect.com/science/article/pii/S1756464624001983

Quercetin in Rheumatoid Arthritis

Study: A double-blind, randomized controlled trial investigated 500 mg/day quercetin supplementation for 8 weeks in women with rheumatoid arthritis. The study measured inflammatory factors and clinical symptoms.

Findings: Quercetin significantly reduced inflammatory markers (e.g., IL-6, CRP) and improved clinical symptoms compared to placebo, suggesting anti-inflammatory benefits.

Link: https://pubmed.ncbi.nlm.nih.gov/27710596/

Quercetin for Metabolic Syndrome Components

Study: A systematic review and meta-analysis of 20 randomized controlled trials (RCTs) with 1,164 participants examined quercetin’s effects on metabolic syndrome components (e.g., fasting blood glucose, blood pressure, lipids). Doses varied, and studies spanned up to December 2023.

Findings: Quercetin significantly reduced fasting blood glucose (-1.03 mg/dL, 95% CI: -1.87 to -0.19) and systolic blood pressure (-1.96 mmHg, 95% CI: -3.11 to -0.81). No significant effects were observed on triglycerides, HDL cholesterol, diastolic blood pressure, or waist circumference.

Link: https://www.sciencedirect.com/science/article/pii/S2666149724000135

Quercetin in Type 2 Diabetes

Study: A double-blind, randomized controlled trial assessed quercetin (500 mg/day) in women with type 2 diabetes, focusing on cardiovascular risk factors and inflammatory biomarkers.

Findings: Quercetin reduced systolic blood pressure and improved inflammatory biomarkers but had no significant effect on fasting serum cholesterol levels or other lipid profiles.

Link: Not directly linked in provided sources, but referenced in (Zahedi et al., 2013).

Quercetin and Dasatinib in Diabetic Kidney Disease

Study: A Phase 1/2 clinical trial tested dasatinib plus quercetin (1000 mg/day) in individuals with diabetic kidney disease to assess senolytic effects (reducing senescent cells). The regimen involved 3 days of treatment with adipose tissue biopsies taken 11 days later.

Findings: The combination reduced senescent cell numbers and inflammation in adipose tissue, suggesting potential benefits for age-related diseases. No significant changes in biomarkers or cognition were noted in a related Alzheimer’s trial.

Link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6733044/

Quercetin in Upper Respiratory Tract Infections (URTI)

Study: A randomized, double-blind, placebo-controlled trial evaluated quercetin (500 or 1000 mg/day) versus placebo in 1002 patients for 12 weeks to assess URTI rates.

Findings: Quercetin showed no significant effect on URTI rates compared to placebo, despite being safe up to 2000 mg/day as assessed by blood profile and lung function.

Link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10609911/

Quercetin with Vitamin C in Athletes

Study: A randomized, double-blind, placebo-controlled trial in 60 male physical education students examined 500 mg quercetin + 250 mg vitamin C, quercetin alone, vitamin C alone, or placebo for 8 weeks. Outcomes included oxidative stress (F2-isoprostane) and inflammatory biomarkers (IL-6, CRP, E-selectin).

Findings: Significant reductions in IL-6, CRP, and F2-isoprostane were observed only in the quercetin + vitamin C group, suggesting synergistic effects with vitamin C for anti-inflammatory and antioxidant activity in athletes.

Link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3429288/