Quercetin 500mg Restores Chronic Gastritis Mucosa by 44% — 12-Week RCT, Antioxidant + NF-κB Multi-Target

A 12-week RCT in 142 chronic gastritis patients taking 500mg of quercetin, the flavonoid abundant in onions, apples, and green tea, showed endoscopic mucosal recovery of +44% and gastric tissue inflammatory cytokines decreasing 34~38%. Published in the October 2025 issue of World Journal of Gastroenterology, the joint trial by Italy’s Milan Medical College and Korea’s Seoul National University Medical College demonstrated quercetin as a multi-target molecule for chronic gastritis for the first time.

Researchers randomized 142 patients (mean 51, H. pylori-positive 58%) with endoscopic moderate to severe chronic gastritis (Sydney classification) to quercetin 500mg (95% standardized extract) or placebo. Primary endpoint was 12-week endoscopic mucosal recovery (Sydney score normalization). Secondary endpoints included gastric tissue cytokines (IL-6, TNF-α, NF-κB), GSRS symptoms, H. pylori conversion, and oxidative stress markers.

At 12 weeks, endoscopic mucosal recovery was 44% in quercetin versus 12% in placebo. The proportion improving by ≥1 Sydney class (severe→moderate, moderate→mild) was 3.7-fold higher in quercetin than placebo. Gastric tissue biopsy showed IL-6 -38%, TNF-α -34%, NF-κB p65 -29%, COX-2 -32% — consistent across PCR and immunohistochemistry methods.

GSRS symptoms fell -42% in quercetin (epigastric pain, dyspepsia, belching, acid reflux all improved evenly), -10% placebo. Among 82 H. pylori-positive patients, conversion was 32% in quercetin versus 14% in placebo (+18 percentage points). Quercetin alone does not match antibiotic eradication efficacy but doubles placebo conversion. It suggests value as an antibiotic adjunct.

Biochemically, gastric tissue oxidative MDA -36%, GSH +32%, SOD +28%, catalase +24% — broad antioxidant system recovery. Quercetin directly neutralizes free radicals while activating the Nrf2 (NF-E2-related factor 2) pathway to upregulate endogenous antioxidant enzyme expression. This dual action distinguishes quercetin from single-target antioxidants.

Quercetin is abundant in onions (especially red and yellow), apple skins, green tea, kale, and berries. Average dietary intake is 15~25mg/day, but the trial’s clinical effect emerged at 500mg. Diet alone cannot reach therapeutic concentration, requiring concentrated extract. The 95% standardized extract (QU995) is the matrix standard.

The mechanism spans five axes. First, direct free radical neutralization. Second, Nrf2 pathway activation increasing GSH, SOD, and catalase. Third, NF-κB direct inhibition reducing IL-6, TNF-α, COX-2. Fourth, mucosal adhesion protein expression for gastric protection. Fifth, partial H. pylori urease inhibition + mucosal adhesion blockade. The pharmacology directly addresses gastritis core pathology (chronic inflammation + oxidative stress + mucosal injury).

Effects reached significance at week 8 and peaked at week 12. In 24-week follow-up, sustained effects produced four-fold lower PPI initiation rate than placebo. Quercetin reduces PPI dependence.

Adverse events were 6.4% in quercetin (mild headache, GI discomfort, week 1 only), 5.6% placebo. However, patients on anticoagulants (warfarin), cyclosporine, or with kidney disease (high-dose nephrotoxicity reports) should consult a clinician. Safety is undetermined in pregnancy and lactation.

Korean chronic gastritis prevalence is 30~40% per 2026 Korean Society of Gastroenterology estimates (35%+ in 40s, 45%+ in 50s) — extremely high. This connects directly to 50~55% H. pylori positivity. Spring 2026 clinical practice positions quercetin 500mg over 12 weeks as a first-line option for patients with chronic gastritis + H. pylori-positive + antibiotic side effects, or those discontinuing PPI. Active bleeding, large ulcer, or gastric cancer family history warrant gastroenterology consultation first.