Quercetin

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HPRC Dietary Supplement Classification System: Quercetin

Background

Quercetin

Quercetin, one of the most abundant natural flavonoids, is present in dietary sources such as berries, apples, onions, broccoli, kale, red wine, and tea.1,2 The intake of quercetin from food sources ranges from five to 40 milligrams per day but could be as much as 200-500 milligrams per day when consumption of fruits and vegetables is high, especially when the peel of the fruit is consumed.1

Quercetin from foods or supplements is readily absorbed into the circulation through the intestines; however, the mechanisms of absorption are not fully understood.3 The maximal blood concentration of quercetin is reached within a few hours of ingestion, with a reported half-life between 11 and 28 hours.2 The key biological functions ascribed to quercetin are its antioxidant, anticarcinogenic, antiviral, anti-inflammatory, psychostimulant, neuroprotective, and cardioprotective properties.1,4-7

Dose Range and Upper Limit

Quercetin

Food and Nutrition Board DRI:

RDA/AI: Not established.

Upper Limit: Not established.

Doses Used In Randomized Clinical Trials: RCTs have safely used up to 1,000 mg of quercetin daily in military members, athletes, and healthy adults for up to three months.8-12

Toxicology Data: No toxicology is available from clinical studies.

Benefits and Risks

Quercetin

Evaluation of Potential Benefits

As a rule, flavonoids are antioxidants. Hence, quercetin has been shown to have free-radical scavenging properties. In addition, quercetin has anticarcinogenic and anti-inflammatory properties.10 These actions have been attributed to quercetin’s potential for reducing the occurrence of cardiovascular, metabolic, and neurodegenerative diseases and cancers.13,14 Studies have investigated the effect of quercetin on endurance performance with mixed results. One study found modest and substantial increases in VO2max and time to fatigue, respectively.10 A couple of studies reported modest improvements in endurance performance with no concomitant increase in VO2max.11,15 Other studies found no improvements in aerobic fitness or other measures of endurance performance.8,9,16 Taken together, the evidence suggests that quercetin may not improve endurance performance. Additional research is needed to fully assess the effects of quercetin on performance.

Potential Detrimental Effects on…

Military Performance: No data found.

Military Survivability: No data found.

Other Health Risks

Quercetin at doses of 1,000 mg or less daily for three months has not been found to have any adverse effects.2,15 The safety of quercetin at doses greater than 1,000 mg/day for a long period of time is unknown.12 The use of quercetin by Warfighters who experience sleep deprivation in combination with negative energy balance, dehydration, and use of non-prescribed supplements or other medications has not been studied and may alter the toxicity thresholds as compared to using it alone under more conventional conditions.12

Interactions with Medications or Other Bioactive Substances

Individuals using quinolone antibiotics and warfarin (Coumadin) should be cautious as quercetin interacts moderately with these medications.16

For details of these and other potential interactions, visit the Natural Medicines Comprehensive Database.16

Withdrawal Effects

No data found.

Concern and Benefit Estimate (see Dietary Supplement Risk Matrix)

Benefit Potential: Low
Risk (safety concern): Minimal
Classification score: 5

There is conflicting evidence on the effect of quercetin on endurance performance.

References

Quercetin

  1. Harwood M, Danielewska-Nikiel B, Borzelleca JF, Flamm GW, et al. A critical review of the data related to the safety of quercetin and lack of evidence of in vivo toxicity, including lack of genotoxic/carcinogenic properties. Food and Chemical Toxicity. 2007;45(11):2179-205.
  2. Committee on Dietary Supplement Use by Military Personnel. Use of dietary supplements by military personnel. Washington, DC: Food and Nutrition Board, Institute of Medicine; 2008.
  3. Murota K, Terao J. Antioxidative flavonoid quercetin: implication of its intestinal absorption and metabolism. Arch Biochem Biophys. 2003;417(1):12-7.
  4. Alexander S. Flavonoids as antagonists at A1 adenosine receptors. Phytother Res. 2006;20(11):1009-12.
  5. Davis JM, Murphy EA, McClellan JL, Carmichael MD, et al. Quercetin reduces susceptibility to influenza infection following stressful exercise. American Journal of Physiology - Regulatory, Integrative and Comparative Physiology. 2008;295(2):R5059.
  6. Egert S, Bosy-Westphal A, Seiberl J, Kurbitz C, et al. Quercetin reduces systolic blood pressure and plasma oxidised low-density lipoprotein concentrations in overweight subjects with a high-cardiovascular disease risk phenotype: a double-blinded, placebo-controlled cross-over study. Br. J Nutr. 2009;102(7):1065-74.
  7. Utesch D, Feige K, Dasenbrock J, Broschard JH, et al. Evaluation of the potential in vivo genotoxicity of quercetin. Mutat. Res. Genet. Toxicol. Environ. Mutagen. 2008;654(1):38-44.
  8. Bigelman KA, Fan EH, Chapman DP, Freese EC, et al. Effects of Six Weeks of Quercetin Supplementation on Physical Performance in ROTC Cadets. Milit. Med. 2010;175(10):791-8.
  9. Cureton KJ, Phillip D. Tomporowski, Singhal A, Pasley JD, et al. Dietary quercetin supplementation is not ergogenic in untrained men. J. Appl. Physiol. 2009;107:(4):1095-104.
  10. Davis JM. The dietary flavonoid quercetin increases VO(2max) and endurance capacity. Int J Sport Nutr Exerc Metab. 2010;20(1):56-62.
  11. Nieman DC, Williams AS, Shanely RA, Jin FX, et al. Quercetin’s Influence on Exercise Performance and Muscle Mitochondrial Biogenesis. Med. Sci. Sports Exerc. 2010;42(2):338-45.
  12. Askew EW, Racette S, Millard-Stafford M, Chen C-Y, et al. Effects of Quercetin on Physical and Cognitive Performance and Human Health: A Status-of-the-Science review. Natick, MA: The U.S. Army Research Institute of Environmental Medicine (USARIEM) and DoD Combat Feeding Directorate, Natick Soldier Research and Development & Engineering Center; 2008.
  13. Davis JM. Effects of the dietary flavonoid quercetin upon performance and health. Curr Sports Med Rep. 2009;8(4):206-13.
  14. Ross JA, Kasum CM. Dietary flavonoids: Bioavailability, metabolic effects, and safety. Annu. Rev. Nutr. 2002;22:19-34.
  15. Okamoto T. Safety of quercetin for clinical application (Review). International Journal of Molecular Medicine. 2005;16(2):275-8.
  16. Jellin J, Gregory, PJ, eds. Quercetin. Natural Medicines Comprehensive Database 2011; http://www.naturaldatabase.com.