Quercetin

• Weak evidenceone or more case studies, supported by animal evidence OR small treatment effects of limited clinical significance OR studies with no controls OR weak trends of effects (this is the CancerChoices definition; other researchers and studies may define this differently) of stabilized lymphocyte counts among people with chronic lymphocytic leukemia or small lymphocytic lymphoma treated with quercetin

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What is your body terrain? ›

• Good evidencesignificant effects in one large or several mid-sized and well-designed clinical studies (randomized controlled trials (RCTs) with an appropriate placebo or other strong comparison control or observational studies that control for confounds) (this is the CancerChoices definition; other researchers and studies may define this differently) of some lower markers of inflammation among people with various noncancer health conditions treated with quercetin
• Modest evidencesignificant effects in at least three small but well-designed randomized controlled trials (RCTs), or one or more well-designed, mid-sized clinical studies of reasonably good quality (RCTs or observational studies), or several small studies aggregated into a meta-analysis (this is the CancerChoices definition; other researchers and studies may define this differently) of lower fasting plasma glucose, although no evidence of an effectoverall, one or more studies did not demonstrate that a treatment or intervention led to an expected outcome; this does not always mean that there is no effect in clinical practice, but that the studies may have been underpowered (too few participants) or poorly designed. Larger, well-designed studies provide more confidence in making assessments. on HbA1c levels or a marker of insulin resistancea condition in which cells in your muscles, fat, and liver don’t respond well to insulin and can’t efficiently take up glucose from your blood for energy, among people with metabolic syndrome and related disorders treated with quercetin
• Preliminary evidencesignificant effects in small or poorly designed clinical studies OR conflicting results in adequate studies but a preponderance of evidence of an effect (this is the CancerChoices definition; other researchers and studies may define this differently) of lower markers of oxidative stressan imbalance between free radicals and antioxidants in your body in which antioxidant levels are lower than normal; this imbalance can cause harmful oxidation reactions in your body chemistry among people treated with quercetin (not specific to cancer)
• No evidence of an effect on measures of body weight among overweight or obese people treated with quercetin in a combined analysis of studies
• Insufficient evidencepreclinical evidence only OR clinical studies with such poor or unclear methodology that no conclusion can be drawn OR conflicting findings across clinical studies with no preponderance of evidence in one direction; conflicting evidence occurs when studies find conflicting effects (positive effect vs no effect or negative effect) with the same treatment and the same general study population (same cancer type, for example) (this is the CancerChoices definition; other researchers and studies may define this differently) of a lower marker of insulin resistance and no evidence of an effect on fasting blood glucose or insulin among women with polycystic ovary syndrome treated with quercetin

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• No evidence of an effectoverall, one or more studies did not demonstrate that a treatment or intervention led to an expected outcome; this does not always mean that there is no effect in clinical practice, but that the studies may have been underpowered (too few participants) or poorly designed. Larger, well-designed studies provide more confidence in making assessments. on incidence of oral mucositisinflammation and ulceration of the mucous membranes lining the digestive tract, usually as an adverse effect of chemotherapy and radiotherapy treatment for cancer among people with blood malignancies treated with quercetin
• Modest evidencesignificant effects in at least three small but well-designed randomized controlled trials (RCTs), or one or more well-designed, mid-sized clinical studies of reasonably good quality (RCTs or observational studies), or several small studies aggregated into a meta-analysis (this is the CancerChoices definition; other researchers and studies may define this differently) of lower blood pressure among people treated with quercetin (not specific to cancer)
• Preliminary evidencesignificant effects in small or poorly designed clinical studies OR conflicting results in adequate studies but a preponderance of evidence of an effect (this is the CancerChoices definition; other researchers and studies may define this differently) of less pain and joint stiffness among women with rheumatoid arthritis (not specific to cancer) treated with quercetin

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• Modest evidencesignificant effects in at least three small but well-designed randomized controlled trials (RCTs), or one or more well-designed, mid-sized clinical studies of reasonably good quality (RCTs or observational studies), or several small studies aggregated into a meta-analysis (this is the CancerChoices definition; other researchers and studies may define this differently) of lower risk of proximal colon cancer, but only among people with high fruit intake or Healthy Eating Index scores, among people eating the highest levels of foods with quercetin, including tea
• Preliminary evidencesignificant effects in small or poorly designed clinical studies OR conflicting results in adequate studies but a preponderance of evidence of an effect (this is the CancerChoices definition; other researchers and studies may define this differently) of lower incidence of recurrence among people with breast cancer, especially obese people, eating higher levels of foods containing quercetin
• Preliminary evidence of lower risk of stomach cancer (gastric adenocarcinoma) among people eating foods with the highest levels of quercetin, with stronger effects for female smokers
• No evidence of an effectoverall, one or more studies did not demonstrate that a treatment or intervention led to an expected outcome; this does not always mean that there is no effect in clinical practice, but that the studies may have been underpowered (too few participants) or poorly designed. Larger, well-designed studies provide more confidence in making assessments. on risk of ovarian cancer among women eating foods with higher levels of quercetin in 2 very large studies
• Preliminary evidence of lower risk of prostate cancer among men with the highest intake of quercetin in foods
• No evidence of an effect on prostate specific antigen (PSA) or PSA doubling time among men with elevated PSA levels treated with quercetin in a small study

See How can quercetin help you? What the research says ›

• Not mentioned in integrative cancer clinical practice guidelines
• Used in several of our program sources
• Used in traditional Chinese medicine treatments

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• Quercetin showed few and generally mild side effects in clinical trials.
• Quercetin may interact with some prescription drugs; moderate caution is needed and supervision by a medical professional is highly recommended by anyone taking these drugs.
• An increased risk of distal colon cancer is seen among people with low levels of fruit intake  eating the highest levels of foods with quercetin.

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• Widely available without restriction
• Generally inexpensive (less than $500 US/year)

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