Quercetin is a flavonol, which is a class of flavonoids [1]. It is a nonessential nutrient.

Foods High in Quercetin

Quercetin naturally occurs in onions, red wine, Ginkgo biloba, green tea, buckwheat tea.

Quercetin Supplements

Quercetin supplements without prescription (over-the-counter) are available.

Quercetin Health Benefits

Quercetin supplements are POSSIBLY EFFECTIVE in reducing pain in prostate inflammation (chronic prostatitis) [2,3] and in lowering triglyceride levels [8].

There is INSUFFICIENT EVIDENCE [2] about the effectiveness of quercetin supplements in the prevention or treatment of asthma, atherosclerosis (artery hardening), cancer (lung, ovarian, pancreatic), cataracts, chronic fatigue syndrome, diabetes mellitus type 2, gastric or duodenal ulcers, gout, hay fever, heart disease, high cholesterol [8], high blood pressure, inflammation [5], pain and swelling, schizophrenia and viral infections, or in improving exercise performance [4,6] or in kidney transplantation.

Quercetin Safety: Toxicity, Side Effects

Quercetin supplements are POSSIBLY SAFE for most people when taken in appropriate amounts by mouth or as intravenous injections short-term (up to 12 weeks) [2].

Side effects may include nausea, headache and tingling [2]. Very high doses may cause kidney damage [2].

Not enough is known about the safety of quercetin supplements during pregnancy and breastfeeding, so women in these periods should avoid them [2].

Quercetin-Drug Interactions

Quercetin supplements may increase the effect of amiodarone, amitriptyline, clarithromycin, codeine, cyclosporin, diclofenac, fentanyl, glipizide, haloperidol, ibuprofen, imipramine, losartan, lovastatin, metoprolol, omeprazole, ondansetron, paclitaxel, paroxetine, phenytoin, piroxicam, propranolol, risperidone, rosiglitazone, sertraline, tamoxifen, tolbutamide, torsemide, tramadol, venlafaxine, verapamil, warfarin and others [2].

  1. Flavonoids  Linus Pauling Institute
  2. Quercetin uses, side effects  WebMD
  3. Shoskes DA et al, 1999, Quercetin in men with category III chronic prostatitis: a preliminary prospective, double-blind, placebo-controlled trial  PubMed
  4. Scholten SD et al, 2013, Long-term quercetin supplementation reduces lipid peroxidation but does not improve performance in endurance runners  PubMed Central
  5. Askari G et al, 2012, The effect of quercetin supplementation on selected markers of inflammation and oxidative stress  PubMed Central
  6. Doneshvar P et al, 2013, Effect of Eight Weeks of Quercetin Supplementation on Exercise Performance, Muscle Damage and Body Muscle in Male Badminton Players  PubMed Central
  7. Kressler J et al, 2011, Quercetin and endurance exercise capacity: a systematic review and meta-analysis  PubMed
  8. Sahebkar A, 2015, Effects of Quercetin Supplementation on Lipid Profile: A Systematic Review and Meta-Analysis of Randomized Controlled Trials  PubMed

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