Quercetin

Also known as: quercetin dihydrate, quercetin phytosome, Quercefit, EMIQ

Grade B — Moderate Evidenceflavonoidlongevityimmune

Recommended Dosage

500–1000 mg

With fatty meal. Morning. Synergistic with vitamin C and zinc.

Versatile flavonoid with senolytic, immune, and anti-inflammatory properties. Zinc ionophore. Phytosome form critical for absorption.

🧬Longevity🛡️Immunity
Last reviewed: 2026-03-09

Evidence Rating: Grade B — Moderate Evidence

Some RCTs with positive results, or strong observational evidence. More research may refine our understanding.

Interaction Warnings

CyclosporineHigh Risk

Inhibits P-glycoprotein; potential toxicity increase

WarfarinModerate

CYP2C9 inhibitor; may increase warfarin levels — monitor INR

Antibiotics (fluoroquinolones)Moderate

May reduce antibiotic absorption — separate by 2+ hours

⚠️ Important Notes

  • Phytosome form has 20x better bioavailability
  • High doses (>3g/day): possible kidney damage
  • Also a zinc ionophore — enhances zinc cellular uptake

Clinical Evidence (3 studies)

Quercetin reduced URTI in athletes

Somerville VS et al. (2016) — Nutrients

Meta-analysis of 5 RCTs: modest but significant URTI prevention

View on PubMed

Quercetin phytosome reduced SARS-CoV-2 infection

Di Pierro F et al. (2021) — Int J Gen Med

Significantly reduced infection rates; RCT

View on PubMed

Quercetin reduced cold/flu symptoms in stressed adults

Heinz SA et al. (2010) — Eur J Nutr

1,000mg/day for 12 weeks reduced URTI sick days

View on PubMed

Related Supplements

Vitamin D3

Grade A — Strong Evidence

Essential hormone precursor. Most people in northern latitudes are deficient. Strong evidence for immunity, bone health, and mood.

NAC (N-Acetyl Cysteine)

Grade B — Moderate Evidence

Precursor to glutathione (master antioxidant). Strong evidence for respiratory health, liver support, and psychiatric conditions.

Vitamin C

Grade A — Strong Evidence

Essential antioxidant vitamin. Supports immune function, collagen synthesis, and antioxidant defense. 50% infection reduction in athletes.

Selenium

Grade B — Moderate Evidence

Essential trace mineral for thyroid function (T4→T3 conversion) and antioxidant defense. Reduces Hashimoto's antibodies.

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⚕️ Important Disclaimer

This information is for educational purposes only. It is not medical advice. Always consult a healthcare provider before starting any supplement regimen, especially if you take medications or have health conditions.

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