What Is Quercetin?

Quercetin (KWAIR-suh-ten) is a flavonoid, a plant-derived compound found in fruits and vegetables. Flavonoids have generated scientific interest because of their potential beneficial effects on human health, including antioxidant, anti-inflammatory, antitumor, and antiviral activities.

Herbs and botanicals have a long history of traditional medicinal use in many countries. Flavonoids were not discovered until the 1930s, but now more than 4,000 types have been identified. In recent years, these naturally occurring substances have been receiving increased attention by researchers, and quercetin in particular has shown great promise.

Quercetin is widely found in apple skins, berries, tea, and red wine. There has been increasing interest in quercetin in the sports science and athletic communities due to scientific and clinical research results that show quercetin’s antioxidant, anti-inflammatory and other properties are likely to improve mental and physical performance. In addition, emerging evidence suggests quercetin may reduce infection risk during intense physical exercise.

To learn more, click here and read "Quercetin: A Scientific Journey of Discovery"

Quercetin: Myths v. Facts

MYTH: No studies have proven that quercetin can improve athletic performance.

FACT: In recent years, there have been several credible clinical studies that have shown that athletes, as well as untrained individuals, can experience increased endurance by consuming quercetin.

  • An independent, randomized, double-blind, placebo-controlled, cross-over study from the University of South Carolina showed that when 12 healthy, active (but not highly trained) men and women consumed 500 mg of quercetin (QU995™) in an enriched drink mix twice daily for 7 days, they experienced a 13.2 percent increase in ride time to fatigue (based on bicycle endurance capacity) and a 3.9 percent increase in VO2max (maximum oxygen consumption).
  • An independent, randomized, double-blind, placebo-controlled, crossover study by researchers at Pepperdine University on the effect of FRS (a liquid antioxidant formula containing quercetin) on cycling performance in eleven elite cyclists showed a 3.1% improvement in time to complete a simulated 30km mountainous time trial when subjects consumed FRS for a 3 week period.
  • An independent, randomized, double-blind, placebo-controlled, cross-over study from Appalachian State University showed that when untrained males consumed 1000 mg of quercetin each day for two weeks they experienced a statistically significant improvement of 2.9% in 12-minute treadmill time trial performance.

MYTH: If you want to achieve the optimal benefits from quercetin, you can simply eat quercetin-rich fruits and vegetables.

FACT: While there are many benefits to consuming quercetin-rich foods, you cannot achieve the endurance benefits such as those found in the University of South Carolina, Pepperdine, and Appalachian State University studies through food and diet alone. For example, in the University of South Carolina and Appalachian State University studies, participants consumed 500 mg of Quercetin twice a day. A large red apple contains about 10 mg of Quercetin, so you’d have to eat 100 apples a day to get the same amount of quercetin.

Click here for all Myths and Facts

An Interview with J. Mark Davis, PhD, FACSM

Dr. Mark Davis discusses animal and human studies with quercetin. Dr. Davis is a Professor and Director of the Exercise Biochemistry Laboratory at the University of South Carolina. He has published more than 110 scientific articles on exercise science.

Bibliography of Quercetin Studies

These sample studies have been published in academic, peer reviewed journals. Thousands of additional quercetin abstracts can be found on PubMed. Click here and search for "Quercetin"

Angeloni C, Spencer JP, Leoncini E, et al. Role of quercetin and its in vivo metabolites in protecting H9c2 cells against oxidative stress. Biochimie. 2007;89:73-82.

Ansari MA, Abdul HM, Joshi G, et al. Protective effect of quercetin in primary neurons against Abeta (1-42): relevance to Alzheimer’s disease. J Nutri Biochem 2008.

Chen L, Li J, Luo C, et al. Binding interaction of quercetin-3-beta-galactoside and its synthetic

Cogolludo A, Frazziano G, Briones AM, et al. The dietary flavonoid quercetin activates BKCa currents in coronary arteries via production of H2O2. Role in vasodilatation. Cardiovasc Res. 2007;73:424-431.

Cureton KJ, Tomporowski PD, Singhal A, et al. Dietary quercetin supplementation is not ergogenic in trained men. J Appl Physiol; In press.

Cushnie TP, Lamb AJ. Antimicrobial activity of flavonoids. Int J Antimicrob Agents. 2005;26:343-356.

Davis JM, Carlstedt CJ, Chen S, Carmichael, MD, Murphy EA. The dietary flavonoid quercetin increases VO2max and endurance capacity. Epub Int J Sports Nutri.

Davis JM, Murphy EA, Carmichael MD. Effects of the dietary flavonoid quercetin upon performance and health. Curr Sports Med Rep. 2009;8:

Davis JM, Murphy EA, Carmichael JD, Davis B. Quercetin increases brain and muscle mitochondrial biogenesis and exercise tolerance. Am J Physiol Regul Integr Comp Physiol. 2009;296:R1071-1077.

Davis, JM, Murphy EA, McClellan JL, et al. Quercetin reduces susceptibility to influenza infection following stressful exercise. Amn J Physiol Regul Integr Comp Physiol. 2008;295:R505-509.

De Boer VC, Dihal AA, van der Woude H, et al. Tissue distribution of quercetin in rats and pigs. J Nutr. 2005;135:1718-1725.

Edwards RL, Lyon T, Litwin SE, et al. Quercetin reduces blood pressure in hypertensive subjects. J Nutr 2007;137:2405-2411.

Egert S, Wolffram S, Bosy-Westphal A, et al. Daily quercetin supplementation dose-dependently increases plasma quercetin concentrations in healthy humans. J Nutr. 2008;138:1615-1621.

Harwood M, Danielewska-Nikiel B, Borzelleca JF, 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 Chem Toxicol. 2007;45:2179-2205.

Henson D, Nieman D, Davis JM, et al. Post-160-km race illness rates and decreases in granulocyte respiratory burst and salivary IgA output are not countered by quercetin ingestion. Int J Sports Med. 2008;29:856-863.

Click here to read the full Bibliography of Quercetin Studies