Quercetin Phytosome as a Dietary Supplement
Quercetin phytosome is not routinely recommended as a dietary supplement for general health purposes, as major clinical guidelines consistently state there is no clear evidence that dietary supplementation with herbs or vitamins improves outcomes in people without underlying deficiencies. 1
Guideline-Based Position on Supplementation
The American Diabetes Association explicitly states that routine supplementation with herbal or nonherbal products (including vitamins, minerals, and botanicals like quercetin) is not recommended for people without underlying deficiency, as there is no benefit demonstrated. 1
The NCCN cancer survivorship guidelines (2025) recommend obtaining nutrients from food sources rather than relying on dietary supplements, stating that routine use of dietary supplements is not recommended for cancer control purposes. 1
The American Heart Association dietary guidelines emphasize that vitamin and mineral supplements are not a substitute for a balanced and nutritious diet, and healthy individuals should obtain adequate nutrient intake from foods. 1
Specific Perioperative Considerations
If you are taking quercetin phytosome and have upcoming surgery, the Society for Perioperative Assessment and Quality Improvement (SPAQI) recommends holding quercetin for 2 weeks before elective procedures. 1
This recommendation is based on quercetin's multiple potential effects and drug interactions, though the specific mechanisms are not fully elucidated in perioperative contexts. 1
The 2-week discontinuation period allows for adequate clearance and minimizes potential interference with anesthetic drugs or perioperative medications. 1
Safety Profile and Potential Risks
While quercetin phytosome demonstrates improved bioavailability compared to standard quercetin (up to 20-fold increase in absorption), long-term safety data for high-dose supplementation (≥1000 mg daily for >12 weeks) remains insufficient. 2, 3
Identified Safety Concerns:
Animal studies suggest quercetin may enhance nephrotoxic effects in predamaged kidneys and potentially promote tumor development in estrogen-dependent cancers. 3
Drug interactions are documented, with quercetin altering bioavailability of certain medications through effects on drug metabolism. 3
Quercetin has antiplatelet effects and should be avoided in patients with thrombocytopenia or bleeding disorders, as it can prolong activated partial thromboplastin time and inhibit platelet aggregation. 4
Potential Risk Groups to Avoid Quercetin:
- Patients with pre-existing kidney disease 3
- Patients with estrogen-dependent cancers (breast, ovarian, endometrial) 3
- Patients on anticoagulants or with bleeding disorders 4
- Patients taking medications metabolized by CYP3A4 or CYP2D6 5
Clinical Context Where Evidence Exists
The research evidence for quercetin phytosome is limited to specific investigational contexts and does not support routine supplementation:
COVID-19 prevention and treatment studies showed potential benefit, but these were small pilot studies requiring confirmation in larger, double-blind, placebo-controlled trials. 6, 7
Improved bioavailability has been demonstrated (plasma levels up to 20 times higher than unformulated quercetin), but this does not translate to established clinical benefit for any specific condition. 2
Mild gastrointestinal side effects (nausea, vomiting, diarrhea) are the most commonly reported adverse effects, though generally well-tolerated in short-term studies. 1
Practical Clinical Approach
Before considering quercetin phytosome supplementation, patients should:
Consult with their healthcare provider, particularly if they have kidney disease, hormone-sensitive cancers, bleeding disorders, or take medications with narrow therapeutic windows. 1, 3
Recognize that a diet rich in fruits, vegetables, and whole grains naturally provides quercetin and other flavonoids without the risks associated with high-dose isolated supplementation. 1
Understand that quality control issues with herbal preparations lack standardization, making interactions and effects unpredictable. 5
If supplementation is pursued despite lack of guideline support, avoid doses exceeding 1000 mg daily and limit duration to less than 12 weeks until long-term safety data becomes available. 3