Quercetin

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

Grade B — Moderate Evidenceflavonoidlongevityimmune
500–1000 mgWith 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: 2026-03-11

Evidence

Grade B

Studies

3

Interactions

3

Forms

1

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

Alternatives to Consider

These supplements target similar goals and may be worth considering alongside or instead of Quercetin.

Taurine

Grade B

Conditionally essential amino acid. Landmark 2023 Science paper showed it extends healthy lifespan in multiple species.

🧬 Longevity

NMN (Nicotinamide Mononucleotide)

Grade B

NAD+ precursor with multiple human RCTs showing elevated blood NAD+ and improved physical performance. Exciting longevity candidate.

🧬 Longevity

NR (Nicotinamide Riboside)

Grade B

NAD+ precursor with strong human RCT evidence for NAD+ elevation. Unique cardiovascular benefits: reduced arterial stiffness and blood pressure.

🧬 Longevity

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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