Quercetin supplement: what the research supports and how to choose
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- Quercetin 500 mg capsules. Best for: Adults who want quercetin without added ingredients. See options on Amazon
- Quercetin with bromelain. Best for: Buyers who prefer the common bromelain combination. See options on Amazon
- Quercetin 1,000 mg capsules. Best for: Adults whose doctor suggested a higher single-capsule amount. See options on Amazon
What quercetin is
Quercetin belongs to a family of plant compounds called bioflavonoids, which give many plants their bright colors. MSK says it is the most common bioflavonoid people eat and acts as an antioxidant. Food sources include onions, apples, black, green and buckwheat tea, red grapes, cherries, raspberries and citrus fruits. It is also found in ginkgo and St. John's wort.
Supplements provide quercetin in capsules, often paired with bromelain, an enzyme from pineapple.
What the research shows
| Use | What the evidence says |
|---|---|
| Seasonal allergies | Lab studies only; no clinical trials (MSK) |
| Blood pressure | Small drops in a 2016 meta-analysis of 7 trials |
| Exercise recovery | Less muscle weakness and damage in some studies |
| Cancer | Not shown to treat or prevent cancer in people |
Allergies. Lab studies show quercetin can block the release of histamine, a key allergy chemical. MSK says clinical trials for allergies have not been conducted, so allergy claims on labels are not backed by human evidence.
Blood pressure. A 2016 meta-analysis in the Journal of the American Heart Association pooled 7 randomized trials with 587 people. Quercetin lowered systolic pressure by about 3 mmHg and diastolic by about 2.6 mmHg, with the effect possibly limited to, or greater at, doses above 500 mg a day. The authors called for more research on clinical relevance.
Exercise. A 2023 meta-analysis in Biology of Sport pooled 13 studies with 249 people, nearly all using 1,000 mg a day. Quercetin sped recovery of muscle function and reduced soreness, a muscle damage marker (creatine kinase) and oxidative stress after intense exercise, though every study had some risk of bias. The authors judged 1,000 mg a day for more than 7 days and up to 12 weeks safe and effective for this use.
Other findings. MSK notes one study found improved symptoms in women with rheumatoid arthritis, while quercetin did not improve heart-related markers or depression after heart attack.
Drug interactions
NOW Foods warns that quercetin may interact with a variety of medications. MSK lists:
- Warfarin. A 79-year-old man on stable warfarin had a high INR (a blood clotting test) after starting quercetin; it returned to normal after he stopped.
- Drugs processed by CYP3A4 or CYP2C19. Quercetin blocked these liver enzymes in lab studies, which could raise levels of many drugs.
- Losartan and tamoxifen. Quercetin raised levels of these drugs in animal or preclinical studies.
- Chemotherapy. Because of its antioxidant effects, quercetin may interfere with some chemotherapy drugs.
If you take any prescription drug, talk with your doctor or pharmacist before using quercetin.
Other safety points
- Kidney problems. NOW Foods advises consulting a physician if you have a medical condition, especially kidney dysfunction.
- Pregnancy and nursing. Consult a physician first.
- Pineapple allergy. Quercetin with bromelain products should be avoided if you are allergic to pineapple.
- Breast cancer. MSK notes quercetin worsened estrogen-induced breast tumors in a mouse study. Ask your oncologist first.
Reading a quercetin label
- Quercetin alone. NOW Foods' Quercetin gives 1,000 mg per 2 capsules, taken daily with a meal.
- Quercetin with bromelain. NOW Foods' version gives 800 mg quercetin and 165 mg bromelain per 2 capsules, taken 20 minutes before meals twice daily, or with food for sensitive stomachs.
- Amount per day. The blood pressure analysis suggested effects mainly above 500 mg a day.
- Immune blends. Many products add zinc, vitamin C, elderberry and other herbs. Each adds amounts and cautions to check.
Food first
Onions, apples, tea, red grapes, cherries, raspberries and citrus all provide quercetin as part of a normal diet. If allergies are your goal, talk with your doctor about treatments with proven benefit and use supplements only as an extra.
What to look for when you buy
Quercetin 500 mg capsules
Best for: Adults who want quercetin without added ingredients
NOW Foods lists 1,000 mg of quercetin per 2 capsules, taken daily with a meal, above the 500 mg level linked to blood pressure effects.
Watch out: Many drug interactions, including warfarin. Ask first if you have kidney problems.
See options on AmazonQuercetin with bromelain
Best for: Buyers who prefer the common bromelain combination
NOW Foods lists 800 mg quercetin and 165 mg bromelain per 2 capsules, taken before meals or with food.
Watch out: Avoid with pineapple allergy. Same drug interaction cautions.
See options on AmazonQuercetin 1,000 mg capsules
Best for: Adults whose doctor suggested a higher single-capsule amount
Higher-strength capsules reduce the number of pills.
Watch out: Follow the label and your doctor's advice. Do not stack with immune blends that also contain quercetin.
See options on AmazonQuestions people ask
- Does quercetin help allergies?
- Lab studies show it blocks histamine release, but MSK says clinical trials for allergies have not been done.
- What is quercetin good for?
- Human studies suggest small blood pressure drops above 500 mg a day and better recovery after hard exercise.
- Why is quercetin paired with bromelain?
- Many products combine them. Bromelain is an enzyme from pineapple, so avoid it if you are allergic to pineapple.
- Can I take quercetin with blood thinners?
- Ask your doctor first. A man on warfarin had a high INR after starting quercetin.
- What foods have quercetin?
- Onions, apples, tea, red grapes, cherries, raspberries and citrus fruits.
Sources
- Quercetin: About Herbs (mskcc.org), Memorial Sloan Kettering Cancer Center
- Effects of Quercetin on Blood Pressure: A Systematic Review and Meta-Analysis of Randomized Controlled Trials (pmc.ncbi.nlm.nih.gov), Journal of the American Heart Association (PMC5015358)
- Quercetin supplementation promotes recovery after exercise-induced muscle damage: a systematic review and meta-analysis of randomized controlled trials (pmc.ncbi.nlm.nih.gov), Biology of Sport (PMC10286622)
- Quercetin 500 mg Veg Capsules (www.nowfoods.com/products/supplements/quercetin-500-mg-veg-capsules), NOW Foods
- Quercetin with Bromelain Veg Capsules (www.nowfoods.com/products/supplements/quercetin-bromelain-veg-capsules), NOW Foods