Laura Pole, RN, MSN, OCNS, BCCT Senior Researcher
Nancy Hepp, MS, BCCT Project Manager
Last updated February 16, 2021.
Also known by these names
The flavonoid quercetin is a natural antioxidant that is found in several foods:
- Black, green and buckwheat tea
- Red grapes
- 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
Managing Side Effects and Promoting Wellness
- 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
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
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.
Quercetin is widely available in food sources and in supplements.
BCCT does not recommend therapies or doses, but only provides information for patients and providers to consider as part of a complete treatment plan. Patients should discuss therapies with their physicians, as contraindications, interactions and side effects must be evaluated. Levels of active ingredients of natural products can vary widely between and even within products. See Quality and Sources of Herbs, Supplements and Other Natural Products.
Clinical trials have not established optimal quercetin dose during or after cancer treatment. Dosage recommendations are available from these sources:
- Solutions 4 Health:
- Bladder Cancer Wellness Plan
- Breast Cancer Wellness Plan
- Colorectal Cancer Wellness Plan
- Lung Cancer Wellness Plan
- Lymphoma Wellness Plan
- Prostate Cancer Wellness Plan
- Natural Medicines Database (requires purchase)
- Also see the protocols below.
Integrative Programs, Protocols and Medical Systems
|For more information about programs and protocols, see our Integrative Programs and Protocols page.|
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.
- Programs and protocols
- Alschuler & Gazella complementary approaches32
- 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
- MacDonald breast cancer program36 advises avoiding quercetin
- McKinney protocols37
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.
Non-cancer Uses of Quercetin
A 2017 review listed these effects and uses of quercetin:41
BCCT has not reviewed the effectiveness of this therapy for non-cancer uses.
Note: BCCT 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.
- Memorial Sloan Kettering Cancer Center’s About Herbs: Quercetin
- TRC Natural Medicines website (subscription is required): in-depth information, ratings of effectiveness and safety and evaluation of specific quercetin products
- Consumer Labs: (subscription required): Quercetin
- Moss Reports (purchase required): Select from the list of cancers down the left side of the page for a report describing uses of conventional, complementary, alternative and integrative therapies related to that cancer. Ralph Moss is among the most knowledgeable and balanced researchers of integrative cancer therapies. The cost of his Moss Reports is not negligible, but many patients find them of considerable value. Moss is also available for consultations.
- Gurdev Parmar and Tina Kaczor: Textbook of Naturopathic Oncology
- Dwight McKee, MD, editor: Clinical Pearls
- Donald I. Abrams, MD, and Andrew T. Weil, MD: Integrative Oncology, 2nd Edition
- Neil McKinney, BSc, ND: Naturopathic Oncology, 3rd Edition
- Lise Alschuler, ND, FABNO, and Karolyn Gazella: The Definitive Guide to Cancer, 3rd Edition
- Keith I. Block, MD: Life over Cancer: The Block Center Program for Integrative Cancer Treatment
- Lone Star Medical Group: Natural Alternative Treatments
- Michael Lerner: Choices In Healing: Integrating the Best of Conventional and Complementary Approaches to Cancer