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Latest Edit: Iva Lloyd, ND 2016-11-11 (EDT)

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Quercetin is a flavanol belonging to 1 of the 5 subgroups of bioflavanoid compounds. Bioflavonoids belong to a subgroup of the polyphenolic subgroup of the phenolic organic compounds found in plants.[1] Quercetin has significant anti-inflammatory effects. It inhibits the synthesis and release of histamine and other inflammatory mediators. It also acts as a powerful antioxidant. It appears that quercetin is the most effective bioflavonoid in terms of its antiviral and anticancer actions.

Food Sources

The following foods contain quercetin:[2], [1]

  • Fruits such as apples, elderberries and the skin of grapes
  • Vegetables such as red onions, hot peppers, kale, and capers
  • Black tea
  • other plant foods


Article The Influence of Quercetin on Exercise Performance and Muscle Mitochondria, 2010 May Natural Medicine [1]

The following are the primary uses for quercetin:[2], [3]

  • Asthma[4], [5], [6]
  • Type II Diabetes: Quercetin has been used for the treatment of a variety of diabetic complications such as diabetic cataracts, peripheral neuropathy, and retinopathy. In the case of cataracts, quercetin acts by inhibiting the enzyme aldose reductase which is responsible for converting extra glucose in the body into sorbitol. Sorbitol accumulates in the lens of the eye, drawing with it water, in order to maintain an osmotic balance. The cells then release important molecules such as amino acids, inositol, glutathione, niacin, vitamin C, magnesium, and potassium. The loss of these compounds make the lens more susceptible to damage and thus lead to cataract formation. Quercetin can act to decrease the amount of sorbitol in the lens. Furthermore, quercetin enhances the secretion of insulin, protects pancreatic beta-cells, and inhibits platelet aggregation.
  • Cancer: Quercetin exhibits anticancer effects against a variety of cancers including squamous cell carcinoma, leukemia, and cancers of the breast, ovaries, pelvic cancers such as colon and rectum, and brain. Human studies are needed to confirm these findings from in vitro studies.
  • It may also be effective in inhibiting tumor formation, such as inhibiting enzymes that stimulate malignant thyroid cells.

As well as upper respiratory tract infections.[1]

Prescribing Considerations

The recommended dosages have not yet been established. To determine what your specific requirements are talk to your naturopathic doctor or other trained medical professional.

Article Enhancing Bioavailability of Quercetin, NDNR; 2013 April
  • Adults: The general dosing is 200-400mg 20 minutes before meals, three times a day.


The specific safety considerations for quercetin include:

  • Drug interactions:
  • Cyclosporin: Co-administration with quercetin increases the bioavailability of orally administered cyclosporin.
  • Nutritient Interactions:


  1. 1.0 1.1 1.2 Schor J (2010)The influence of quercetin on exercise performance and muscle mitochondria Natural Medicine Journal. Retrieved March 31, 2012, from http://www.naturalmedicinejournal.com/article_content.asp?edition=1&section=2&article=95.
  2. 2.0 2.1 2.2 Gaby AR (2011) Nutritional Medicine, Fritz Perlberg Publishing.
  3. Murray, MT (1996) Encyclopedia of Nutritional Supplements: The Essential Guide for Improving Your Health Naturally, Prima Publishing.
  4. Rogerio AP, Kanashiro A, Fontanari C, da Silva EV, Lucisano-Valim YM, Soares EG, Faccioli LH (Oct 2007) Anti-inflammatory activity of quercetin and isoquercitrin in experimental murine allergic asthma. Inflamm Res;56(10):402-8. PMID: 18026696,
  5. Moon H, Choi HH, Lee JY, Moon HJ, Sim SS, Kim CJ (Jun 2008) Quercetin inhalation inhibits the asthmatic responses by exposure toaerosolized-ovalbumin in conscious guinea-pigs. Arch Pharm Res;31(6):771-8. PMID: 18563360.
  6. Shaik YB, Castellani ML, Perrella A, et al. (Jul-Dec 2006) Role of quercetin (a natural herbal compound) in allergy and inflammation. J Biol Regul Homeost Agents;20(3-4):47-52. PMID: 18187018/