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Quercetin is the most well researched of all bioflavonoids. It is not actually that good of a supplement on its own, but is an interesting research topic. Tons of interactions, and synergistic with other bioflavonoids and increases absorption of Resveratrol and Green Tea Catechins.

Our evidence-based analysis on quercetin features 79 unique references to scientific papers.

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Summary of Quercetin

Primary information, health benefits, side effects, usage, and other important details

Quercetin is a bioflavonoid found in fruits and vegetables, but highest levels are found in apples and onions.

Like many other bioflavonoids, Quercetin has anti-oxidant, anti-artherogenic, and anti-carcinogenic properties. Quercetin is also neuroactive, with some of the same abilities as caffeine but less potent.

There is a divide between the effects seen in quercetin in in vitro (cell cultured) studies and in vivo (in living) studies, with cell studies showing great results that are not that amazing in humans or animals. This is mostly due to quercetin having low oral bioavailability (low percentage of the compound is absorbed and put to use), but could also be due to in vitro studies using a form of quercetin called 'quercetin aglycone' whereas this particular form is never found in the blood, even after ingested, as it it gets changed in the liver.

Many studies also note a high range of differences between people who ingest the same amount of quercetin, suggesting a large degree of variability is possible with supplementation.

Quercetin has GRAS (Generally Recognized As Safe) status, and no side-effects have yet been noted in doses of a few grams a day in either humans or animals.

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How to Take

Recommended dosage, active amounts, other details

Dosages of quercetin used are in the range of 12.5 to 25mg per kg body weight, which translates to a range of 1,136-2,272mg daily consumption of quercetin when in isolation.

It is suggested to supplement with other bioflavonoids such as resveratrol, genistein, or green tea catechins to increase the potency synergistically and theoretically get the benefits at a reduced level of intake.

When looking for quercetin, the form of dihydrate has the apparent best bioavailability followed by glycosides, aglycone, and finally rutinoside.

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Human Effect Matrix

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The Human Effect Matrix summarizes human studies to tell you what effects Quercetin has on your body, how much evidence there is, and how strong these effects are.

Full details are available to Examine members.
Grade Level of Evidence
Robust research conducted with repeated double-blind clinical trials
Multiple studies where at least two are double-blind and placebo controlled
Single double-blind study or multiple cohort studies
Uncontrolled or observational studies only
Level of Evidence
? The amount of high quality evidence. The more evidence, the more we can trust the results.
Outcome Magnitude of effect
? The direction and size of the supplement's impact on each outcome. Some supplements can have an increasing effect, others have a decreasing effect, and others have no effect.
Consistency of research results
? Scientific research does not always agree. HIGH or VERY HIGH means that most of the scientific research agrees.
grade-b - High See all 3 studies
No acute alterations in blood pressure following Quercetin supplementation
grade-c Notable - See study
The exercise-induced increase in HSP70 expression is abolished with quercetin preloading
grade-c Minor Moderate See 2 studies
May reduce oxidative biomarkers in serum and urine, but is a tad unreliable in doing so.
grade-c Minor - See 2 studies
An increase in HDL-C has been noted following quercetin supplementation
grade-c Minor - See study
An increase in the amount of intestinal permeability induced by training in the heat has been noted with quercetin supplementation, which is an adverse event; the influence of quercetin at rest is uncertain
grade-c Minor - See 2 studies
A decrease in LDL-C has been noted in persons with high blood lipids, although this decrease is not observed in persons who do not have high LDL-C concentrations.
grade-c - - See study
Urinary 8-isoPGF2α is unchanged with prolonged quercetin supplementation.
grade-c - Very High See 2 studies
No significant influence on anaerobic exercise capacity when preloaded
grade-c - - See study
No significant alterations in blood glucose are detected with quercetin supplementation.
grade-c - - See study
No significant alterations in fat oxidation noted with quercetin supplementation
grade-c - - See study
No significant influence on fatigue nor vitality in otherwise healthy persons
grade-c - - See study
No significant influence on heart rate either acutely or with prolonged supplementation.
grade-c - - See study
Hydration during exercise in the heat is unaffected by quercetin supplementation.
grade-c - - See study
Mixed influence on inflammation, but does not appear to at all be practically significant
grade-c - - See study
The alterations in IL-6 concentrations seen with exercise are unchanged with quercetin supplementation.
grade-c - - See study
No significant influence on metabolic rate following acute Quercetin supplementation
grade-c - - See 2 studies
grade-c - - See study
No significant influence on sleep quality
grade-c - - See study
Training volume does not appear to be significantly influenced with quercetin supplementation.
grade-c - - See study
No significant influence on uric acid concentrations
grade-c - - See study
No significant alterations detected in body weight with quercetin supplementation.
grade-c - - See study
No significant changes in vLDL-C are detected with quercetin supplementation.
grade-d Minor - See study
An increase in total cholesterol has been noted, but mostly attributed to HDL

Studies Excluded from Consideration

  • Confounded with other nutraceuticals[1][2]

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Things to Note

Is a Form Of

Also Known As

Apple extract, 3, 4, 5, 7-pentahydroxylflavone

Goes Well With

  • Other bioflavonoids such as Genistein and Resveratrol, due to AMPK activation (in the cell) or by increasing bioavailability (in the gut)

  • Green Tea due to catechol-o-methyl transferase inhibition, and increasing bioavailability of Green Tea Catechins

  • Apigenin in regards to reducing Aromatase transcription

  • Quercetin (as dehydrated powder) is yellow colored

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Click here to see all 79 references.