Quercetin Daily Dose: Recommendations & Effects

What Is Quercetin?

Quercetin is a naturally occurring plant pigment belonging to the flavonoid group, found in many fruits and vegetables. It is a potent antioxidant with well-documented anti-inflammatory, antiviral, and immune-modulating properties. As a dietary supplement, quercetin is widely used to support immune function, relieve allergy symptoms, and promote cardiovascular health.

Natural Sources of Quercetin

Quercetin is found in a wide variety of plant-based foods. The richest dietary sources include:

• Onions (especially red onions)
• Capers (the highest known concentration)
• Apples (with skin)
• Broccoli
• Berries (e.g., blueberries, cranberries)
• Green and black tea
• Red wine

Through a balanced diet, an average adult consumes approximately 10 to 100 mg of quercetin per day.

Recommended Quercetin Daily Dose

There is currently no officially established daily intake value for quercetin from regulatory bodies such as the WHO or EFSA (European Food Safety Authority). Dosages used in clinical studies and expert recommendations vary depending on the intended purpose:

• General antioxidant support: 250–500 mg per day
• Anti-inflammatory and immune support: 500–1000 mg per day
• Allergy relief: 200–400 mg, two to three times daily
• Cardiovascular health: 150–500 mg per day

Most clinical trials report that daily doses between 500 mg and 1000 mg are effective and well tolerated. Higher doses of up to 3000 mg per day have been investigated in some studies but should only be taken under medical supervision.

Bioavailability and Intake Recommendations

In its pure form, quercetin has relatively low bioavailability, meaning the body can only absorb a limited amount. Several strategies are used to improve absorption:

• Quercetin phytosome: Quercetin bound to phosphatidylcholine, which significantly enhances absorption.
• Combination with bromelain or vitamin C: These combinations are common in supplements and may enhance the overall effect.
• Taking with a fatty meal: Dietary fat supports the absorption of the fat-soluble components of quercetin.

It is generally recommended to take quercetin supplements with meals to improve tolerability and optimize absorption.

Side Effects and Safety

Quercetin is considered safe and well tolerated at standard doses of up to approximately 1000 mg per day. At higher doses, the following side effects have occasionally been reported:

• Headaches
• Tingling sensations in the extremities
• Stomach irritation or nausea
• At very high doses: potential stress on the kidneys

People with kidney disease, pregnant women, and breastfeeding mothers should only take quercetin supplements after consulting a healthcare professional.

Interactions with Medications

Quercetin may interact with certain medications. Known interactions include:

• Antibiotics: Quercetin may interfere with the activity of certain antibiotics, particularly quinolones.
• Blood thinners (e.g., warfarin): Quercetin may potentially enhance the effect of anticoagulants.
• Cyclosporine and other immunosuppressants: Quercetin may affect the metabolism of these drugs.
• CYP3A4 enzyme substrates: Quercetin inhibits this liver enzyme, potentially slowing the breakdown of various medications.

Anyone taking prescription medications is strongly advised to consult a doctor before starting quercetin supplementation.

References

1. Mlcek J. et al. - Quercetin and Its Anti-Allergic Immune Response. Molecules, 2016. Available at: https://pubmed.ncbi.nlm.nih.gov/27187333/
2. Anand David AV et al. - Overviews of Biological Importance of Quercetin: A Bioactive Flavonoid. Pharmacognosy Reviews, 2016. Available at: https://pubmed.ncbi.nlm.nih.gov/27041870/
3. European Food Safety Authority (EFSA) - Scientific Opinion on the safety of quercetin as a food supplement. EFSA Journal, 2011. Available at: https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2011.2279