> Research summary—not medical advice. This page synthesizes published research on a mechanism-level intervention. It is not a clinical recommendation.
Consult a qualified healthcare provider before making any changes to diet, supplementation, or treatment.
Intervention Summary#
Quercetin is a flavonoid polyphenol with dual anti-inflammatory and metal-chelating properties. Inhibits NF-kB p65 and IL-8 signaling pathways. Chelates transition metals (copper(II) (Cu2+), iron(II) (Fe2+)/iron(III)) to reduce Fenton-mediated oxidative damage.
Gut bacteria metabolize quercetin into bioactive phenolic acids, creating a bidirectional interaction between supplementation and microbiome ecology.
Evidence#
Inflammation: RCTs demonstrate reduced CRP and TNF-alpha with quercetin 500-1000mg/day in metabolic syndrome and inflammatory conditions. Cardiovascular: Reduces blood pressure (meta-analysis: -3.0 mmHg systolic), LDL oxidation, and endothelial dysfunction. Immune function: Reduces upper respiratory infection incidence and severity in athletes under physical stress.
Microbiome interaction: Quercetin glycosides are hydrolyzed by gut bacterial beta-glucosidases; aglycone is further metabolized to 3,4-dihydroxyphenylacetic acid by Eubacterium and Clostridium species.
Mechanism#
NF-kB inhibition: Quercetin blocks IKK-mediated phosphorylation of IkB-alpha, preventing NF-kB p65 nuclear translocation and downstream inflammatory gene expression. Metal chelation: Binds copper(II) (Cu2+) and iron(II) (Fe2+)/iron(III) at the catechol and carbonyl groups, reducing free metal availability for Fenton reactions and pathogen metal acquisition.
Microbiota modulation: Acts as a prebiotic-like substrate for beneficial bacteria; increases Bifidobacterium and Lactobacillus while reducing Enterobacteriaceae in animal models. Mast cell stabilization: Inhibits histamine release from mast cells, relevant to conditions with mast cell activation.
Clinical Context#
Quercetin has poor oral bioavailability (~2%) unless formulated with absorption enhancers (bromelain, vitamin C, phytosomal delivery). Typical dose: 500-1000mg/day in divided doses. The metal-chelating property makes it particularly relevant in conditions where transition metal excess drives pathology.
Safe and well-tolerated; rare reports of headache at high doses.
> Educational content, not medical advice. This page describes mechanisms by which the intervention interacts with the microbiome and metal ecology. It is not a treatment recommendation.
Clinical decisions about any intervention should be made with a qualified healthcare practitioner who knows your individual history.
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