We’re busy reviewing the evidence on quercetin. While we’re working, we share the original summary from our predecessor website, Beyond Conventional Cancer Therapies.

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Quercetin

The flavonoid quercetin is a natural antioxidant that is found in several foods:

  • Apples
  • Black, green and buckwheat tea
  • Onions
  • Red grapes
  • Cherries
  • Raspberries
  • Citrus fruits

Quercetin is also found in some medicinal plants such as ginkgo biloba and St. John’s Wort. It is also available as a supplement.

Treating the Cancer

Working against cancer growth or spread, improving survival, or working with other treatments or therapies to improve their anticancer action

Studies have found both benefits and concerns regarding effects of quercetin on cancer. Concerns are listed in the Cautions section below.

Lab and Animal Evidence

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Managing Side Effects and Promoting Wellness

Clinical Evidence

  • Reduced fatigue and other common side effects of sunitib when isoquercetin was  used with vitamin C and vitamin B3 among people with kidney cancer17

Lab and Animal Evidence

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Reducing Risk

  • Reducing the risk of developing cancer or the risk of recurrence
  • Reduced risk of all cancers combined, breast and ovarian cancers with high dietary intake of quercetin or of flavanols including quercetin19 
  • No reduced risk of ovarian cancer was found at at levels commonly consumed in a typical diet.20
  • Reduced risk of colorectal cancer in epidemiological and case-control studies with increasing intake of quercetin or of flavanols including quercetin21
  • Reduced risk of lung cancer in epidemiological studies22
  • Reduced risk of smoking-related cancers (lung cancer and aerodigestive tract cancer such as oral and esophageal cancers) in smokers, but not nonsmokers23

Optimizing Your Terrain

  • Quercetin either increased or decreased aromatase enzyme activity in adrenocortical carcinoma cells, depending on dose.24
  • uppressed tumor-promoting responses in breast cancer cells.25
  • No impact on markers of inflammation26
  • May have either a protective or damaging effect of reactive oxygen species on DNA, depending dose or on the concentration of chelating metal ions27

Cautions

Quercetin is relatively nontoxic and is considered “possibly safe” orally in doses of 500 mg or less.28 However, quercetin can cause side effects and drug interactions.29

Quercetin may interfere with the actions of some chemotherapy drugs.30 Consult with your pharmacist for interactions and discuss using quercetin with your doctor. See The Definitive Guide to Cancer, 3rd Edition: An Integrative Approach to Prevention, Treatment, and Healing, page 170, for a list of chemotherapy drugs that interact with quercetin and with which quercetin should not be taken.

In lab and animal studies, quercetin has shown worrisome effects, blocking cell death (apoptosis) in one lab study and worsening estrogen-induced breast tumors in one animal study.31

Access

Quercetin is widely available in food sources and in supplements.

Dosing

Integrative Programs, Protocols and Medical Systems

Integrative oncology clinicians such as Keith Block, Dwight McKee and Lise Alschuler incorporate quercetin supplementation into care during active cancer treatment and/or in post-treatment care to prevent recurrence or secondary cancers.

  • Alschuler & Gazella complementary approaches32
    • Colon cancer
    • Melanoma
    • Ovarian cancer
    • Prostate cancer
    • Soft tissue sarcomas
    • Thyroid cancer
  • Bastyr University Integrative Oncology Research Center protocol for stage IV breast cancer33
  • Block program34
    • Anti-inflammatory terrain modification
    • Chemotherapy enhancement
    • Natural molecular target modification
    • Reduction of risk of secondary cancers
  • Lemole, Mehta & McKee protocols35
    • Bladder cancer
    • Breast cancer
    • Colorectal cancer
    • Lung cancer
    • Lymphoma
    • Prostate cancer
  • MacDonald breast cancer program36 advises avoiding quercetin
  • McKinney protocols37
    • Brain/nerve cancer
    • Breast cancer
    • Cervical cancer
    • Colorectal cancer
    • Leukemia
    • Lung cancer
    • Melanoma
    • Ovarian cancer
    • Pancreatic cancer
    • Skin cancer
    • Thyroid cancer
    • Uterine cancer

Commentary

Integrative oncologist and BCCT advisor Dr. Keith Block uses quercetin as a natural molecular target modifier (IGF-I). Targeted therapies home in on particular growth pathways that cancer cells use to proliferate while sparing normal cells.38 Dr. Block also uses quercetin in multiple vitamin combinations, including with vitamin C to tackle inflammation alterations of the terrain of the human body.39 Quercetin may also help manage cancer-related and/or treatment-related symptoms such as diarrhea and depression.40 Please see Dr. Block’s book for details: Life over Cancer: The Block Center Program for Integrative Cancer Treatment.

Note: CancerChoices has not conducted an independent review of research of quercetin. This summary draws primarily from Memorial Sloan Kettering Cancer Center’s About Herbs and other sources as noted.

Resources

References

  1. Haghi A, Azimi H, Rahimi R. A comprehensive review on pharmacotherapeutics of three phytochemicals, curcumin, quercetin, and allicin, in the treatment of gastric cancer. Journal of Gastrointestinal Cancer. 2017 Dec;48(4):314-320.
  2. Block KI. Life Over Cancer. New York: Bantam Dell. 2009. p. 486
  3. Aiyer HS, Warri AM, Woode DR, Hilakivi-Clarke L, Clarke R. Influence of berry polyphenols on receptor signaling and cell-death pathways: implications for breast cancer prevention. Journal of Agricultural and Food Chemistry. 2012 Jun 13;60(23):5693-708.
  4. Hashemzaei M, Delarami Far A et al. Anticancer and apoptosis‑inducing effects of quercetin in vitro and in vivo. Oncology Reports. 2017 Aug;38(2):819-828.
  5. Li S, Zhao Q et al. Quercetin reversed MDR in breast cancer cells through down-regulating P-gp expression and eliminating cancer stem cells mediated by YB-1 nuclear translocation. Phytotherapy Research. 2018 Aug;32(8):1530-1536; Li S, Yuan S et al. Quercetin enhances chemotherapeutic effect of doxorubicin against human breast cancer cells while reducing toxic side effects of it. Biomed Pharmacother. 2018 Apr;100:441-447.
  6. Iriti M, Kubina R et al. Rutin, a quercetin glycoside, restores chemosensitivity in human breast cancer cells. Phytotherapy Research. 2017 Oct;31(10):1529-1538.
  7. Hashemzaei M, Delarami Far A et al. Anticancer and apoptosis‑inducing effects of quercetin in vitro and in vivo. Oncology Reports. 2017 Aug;38(2):819-828.
  8. Scambia G, Ranelletti FO et al. Quercetin potentiates the effect of adriamycin in a multidrug-resistant MCF-7 human breast-cancer cell line: P-glycoprotein as a possible target. Cancer Chemotherapy and Pharmacology. 1994;34(6):459-64; Wang G, Zhang J, Liu L, Sharma S, Dong Q. Quercetin potentiates doxorubicin mediated antitumor effects against liver cancer through p53/Bcl-xl. PLoS One. 2012;7(12):e51764.
  9. Iriti M, Kubina R et al. Rutin, a quercetin glycoside, restores chemosensitivity in human breast cancer cells. Phytotherapy Research. 2017 Oct;31(10):1529-1538.
  10. Malik A, Sultana M, Qazi A, Qazi MH, Parveen G, Waquar S, Ashraf AB, Rasool M. Role of natural radiosensitizers and cancer cell radioresistance: an update. Analytical Cellular Pathology (Amsterdam). 2016;2016:6146595.
  11. Kuppusamy P, Yusoff MM et al. Nutraceuticals as potential therapeutic agents for colon cancer: a review. Acta Pharm Sin B. 2014 Jun;4(3):173-81.
  12. Scambia G, Ranelletti FO et al. Quercetin potentiates the effect of adriamycin in a multidrug-resistant MCF-7 human breast-cancer cell line: P-glycoprotein as a possible target. Cancer Chemotherapy and Pharmacology. 1994;34(6):459-64; Wang G, Zhang J, Liu L, Sharma S, Dong Q. Quercetin potentiates doxorubicin mediated antitumor effects against liver cancer through p53/Bcl-xl. PLoS One. 2012;7(12):e51764.
  13. Chan MM, Fong D, Soprano KJ, Holmes WF, Heverling H. Inhibition of growth and sensitization to cisplatin-mediated killing of ovarian cancer cells by polyphenolic chemopreventive agents. Journal of Cellular Physiology. 2003 Jan;194(1):63-70.
  14. Yang F, Song L et al. Quercetin in prostate cancer: chemotherapeutic and chemopreventive effects, mechanisms and clinical application potential (Review). Oncology Reports. 2015 Jun;33(6):2659-68.
  15. Tummala R, Lou W, Gao AC, Nadiminty N. Quercetin targets hnRNPA1 to overcome enzalutamide resistance in prostate cancer cells. Molecular Cancer Therapeutics. 2017 Dec;16(12):2770-2779.
  16. Haghi A, Azimi H, Rahimi R. A comprehensive review on pharmacotherapeutics of three phytochemicals, curcumin, quercetin, and allicin, in the treatment of gastric cancer. Journal of Gastrointestinal Cancer. 2017 Dec;48(4):314-320.
  17. Buonerba C, De Placido P et al. Isoquercetin as an adjunct therapy in patients with kidney cancer receiving first-line sunitinib (QUASAR): results of a phase I trial. Frontiers in Pharmacology. 2018 Mar 16;9:189. 
  18. Fischer N, Seo EJ, Efferth T. Prevention from radiation damage by natural products. Phytomedicine. 2018 Aug 1;47:192-200.
  19. Mokbel K, Mokbel K. Chemoprevention of breast cancer with vitamins and micronutrients: a concise review. In Vivo. 2019 Jul-Aug;33(4):983-997.
  20. Parvaresh A, Razavi R et al. Quercetin and ovarian cancer: an evaluation based on a systematic review. Journal of Research in Medical Sciences. 2016 May 9;21:34.
  21. Chang H, Lei L et al. Dietary flavonoids and the risk of colorectal cancer: an updated meta-analysis of epidemiological studies. Nutrients. 2018 Jul;10(7):950; Kocic B, Kitic D, Brankovic S. Dietary flavonoid intake and colorectal cancer risk: evidence from human population studies. Journal of B.U.ON.: Official Journal of the Balkan Union of Oncology. Jan-Mar 2013;18(1):34-43.
  22. Murakami A, Ashida H, Terao J. Multitargeted cancer prevention by quercetin. Cancer Letters. 2008 Oct 8;269(2):315-25.
  23. Woo HD, Kim J. Dietary flavonoid intake and smoking-related cancer risk: a meta-analysis. PLoS One. 2013 Sep 19;8(9):e75604.
  24. Khan SI, Zhao J, Khan IA, Walker LA, Dasmahapatra AK. Potential utility of natural products as regulators of breast cancer-associated aromatase promoters. Reproductive Biology and Endocrinology. 2011 Jun 21;9:91.
  25. Yasuda MT, Sakakibara H, Shimoi K. Estrogen- and stress-induced DNA damage in breast cancer and chemoprevention with dietary flavonoid. Genes and Environment. 2017 Feb 1;39:10.
  26. Peluso I, Raguzzini A, Serafini M. Effect of flavonoids on circulating levels of TNF-α and IL-6 in humans: a systematic review and meta-analysis. Molecular Nutrition & Food Research. 2013 May;57(5):784-801.
  27. Yasuda MT, Sakakibara H, Shimoi K. Estrogen- and stress-induced DNA damage in breast cancer and chemoprevention with dietary flavonoid. Genes and Environment. 2017 Feb 1;39:10; Griffiths K, Aggarwal BB et al. Food antioxidants and their anti-inflammatory properties: a potential role in cardiovascular diseases and cancer prevention. Diseases. 2016 Aug 1;4(3). pii: E28.
  28. TRC Natural Medicines Database. Quercetin: Monograph. Viewed December 28, 2017.
  29. Andres S, Pevny S et al. Safety aspects of the use of quercetin as a dietary supplement. Molecular Nutrition & Food Research. 2017 Nov 11.
  30. Alschuler LN, Gazella KA. The Definitive Guide to Cancer, 3rd Edition: An Integrative Approach to Prevention, Treatment, and Healing. Berkeley, California: Celestial Arts. 2010. p. 170.
  31. Alschuler LN, Gazella KA. The Definitive Guide to Cancer, 3rd Edition: An Integrative Approach to Prevention, Treatment, and Healing. Berkeley, California: Celestial Arts. 2010. p. 170.
  32. Alschuler LN, Gazella KA. The Definitive Guide to Cancer, 3rd Edition: An Integrative Approach to Prevention, Treatment, and Healing. Berkeley, California: Celestial Arts. 2010; Alschuler LN, Gazella KA. The Definitive Guide to Thriving after Cancer: A Five-Step Integrative Plan to Reduce the Risk of Recurrence and Build Lifelong Health. Berkeley, California: Ten Speed Press. 2013.
  33. McKinney N. Naturopathic Oncology, Fourth Edition. Victoria, BC, Canada: Liaison Press. 2020.
  34. Block KI. Life over Cancer: The Block Center Program for Integrative Cancer Treatment. New York: Bantam Dell. 2009.
  35. Lemole G, Mehta P, McKee D. After Cancer Care: The Definitive Self-Care Guide to Getting and Staying Well for Patients with Cancer. New York, New York: Rodale, Inc. 2015.
  36. MacDonald B. The Breast Cancer Companion: A Complementary Care Manual: Third Edition. (self-published, Amazon, 2016).
  37. McKinney N. Naturopathic Oncology, Fourth Edition. Victoria, BC, Canada: Liaison Press. 2020.
  38. Block KI. Life over Cancer: The Block Center Program for Integrative Cancer Treatment. New York: Bantam Dell. 2009. p. 525.
  39. Block KI. Life Over Cancer. New York: Bantam Dell. 2009. pp. 337 and 341.
  40. Block KI. Life over Cancer: The Block Center Program for Integrative Cancer Treatment. New York: Bantam Dell. 2009. p. 143; Memorial Sloan Kettering. About Herbs: Quercetin. December 6, 2016. viewed December 28, 2017.
  41. Anand David AV, Arulmoli R, Parasuraman S. Overviews of biological importance of quercetin: a bioactive flavonoid. Pharmacognosy Reviews. 2016 Jul-Dec;10(20):84-89.