For ATHLETIC PERFORMANCE, quercetin with bromelain can improve endurance by increasing the number of mitochondria and by boosting oxygen delivery to tissues. It protects the lungs and sinuses against infection and allergies, especially helpful for exercising outdoors. The combination of quercetin with bromelain has anti-inflammatory actions that counteract the physiological stressors on athletes’ bodies. Research indicates that quercetin is also a potent antioxidant that scavenges free radicals to reduce tissue and DNA damage, especially for endurance athletes.

Quercetin is a flavonol, one member of the flavonoid group of plant-based antioxidants that give plants their color. Flavonoids belong to a class of micronutrients called polyphenols, which have powerful health benefits. Quercetin is sometimes referred to as the “master flavonoid” both because it is well-researched, and because it is abundant in dark, vibrant-colored vegetables, fruits, nuts, honey, and medicinal herbs. Although there are dietary sources of quercetin, it is hard to consume sufficient quantities in food to reach a therapeutic level.

 Quercetin combined with bromelain brings multiple benefits for peak athletic performance. For the circulatory system, it shields red blood cells from oxidative stress, which boosts oxygen delivery to all tissues. Very importantly, quercetin increases the number and efficiency of mitochondria, the energy-producing factories found in cells, providing a profound boost to muscles, the heart and circulation, the central nervous system and entire metabolism, and improving endurance.

Quercetin is a classic remedy for preventing asthma and nasal allergies, which is particularly useful for exercising outdoors or in gyms where triggers such as grass, dust, or air fresheners can lead to reactive airway symptoms. For the respiratory system, quercetin stabilizes the membranes of mast cells within connective tissues. This discourages mast cells from releasing histamine or inflammatory cytokines that start the allergy or asthma process.

As a powerful antioxidant, quercetin shows promising benefits for scavenging oxygen free radicals, and for neutralizing reactive molecules of nitrogen, thereby reducing tissue and DNA damage. Free radicals are unstable molecules that form when atoms or molecules gain or lose electrons. These unstable free radicals have unpaired electrons, which seek other atoms or molecules to bond to. If they attach to tissues free radicals cause damage, called oxidative stress. Ongoing oxidative stress can injure muscles, organs, and cells. Eventually this results in degenerative disorders, slower metabolism, tissue damage, and symptoms of aging such as wrinkles. Exercise generates more free radicals, but quercetin can enhance the body’s mechanisms to remove them and shield tissues from oxidative damage.

Quercetin also has the ability to calm and balance the body’s inflammatory pathways, and to down-regulate enzymes and hormones responsible for excessive inflammatory responses. While inflammation is critical for tissue repair and for defending against invading microbes, if it becomes over-active it can increase pain, slow down muscle recovery after exercise, and eventually cause organ and cellular damage.

Numerous clinical trials have examined quercetin’s protective effects specifically with athletes, because prolonged and intensive physical exertion exacerbates oxidative damage and inflammation, which mimics the physiological stress of trauma and surgery. A treatment such as quercetin that benefits inflammation and oxidative damage in athletes could potentially help diseases caused by these factors, and also encourage healing of injuries.

In vitro research and human epidemiologic studies confirm the long list of desirable health effects from quercetin. These also include antibacterial actions, and protection for the immune and cardiovascular systems via its antioxidant and anti-inflammatory benefits. Quercetin has an extra benefit for athletes: it helps heal injuries that inevitably occur on a microscopic level in connective and muscle tissues, as well as obvious sprains or hurts.

Quercetin has a key role in improving immune function. For endurance athletes, performing extreme exercise lowers immune protection, leaving them at higher risk of upper respiratory tract infection. In a 2007 study, ultra-marathon runners who competed in a 160-kilometer endurance run were given either 1000mg of quercetin daily or placebo, for three weeks prior to the race. Quercetin supplementation yielded a statistically significant reduction in post exertion upper respiratory infections, which were a full two-thirds, or 66%, lower in the group who took quercetin versus placebo.1 However, the study did not measure significant effects on post-race inflammation or oxidative stress.

Athletic endurance can be significantly enhanced by quercetin. In a 2010 study published in the International Journal of Sports Nutrition and Exercise Metabolism, quercetin’s effects on endurance were measured in healthy volunteers riding bicycles. For seven days, 12 subjects received either 500mg of quercetin or a placebo. Their performance was recorded, and quercetin supplementation led to a 13.2% increase in the amount of time subjects could ride before exhaustion. Also, the quercetin group enjoyed a nearly 4% increase in V02 max, a measure of aerobic fitness.2 VO2 max, or maximal oxygen uptake, is the maximum amount of oxygen a body can utilize during intense exercise. It is a marker of an athlete’s aerobic endurance during training.

Experiments have found that quercetin can increase mitochondria density in muscle tissue by up to 50% in a period of weeks, resembling the effect of regular endurance exercise. Elevations in mitochondria density can be triggered by a number of plant polyphenols including quercetin.4 To competitive athletes, even minute changes in performance may be the difference between winning or losing.

Mitochondrial boosting and improved endurance may be more apparent in untrained exercisers. With that thought, researchers in a 2010 study tested the theory that quercetin may have a larger effect on mitochondrial biogenesis and endurance performance in untrained compared to exercise-trained subjects. Utilizing a randomized, crossover design with 26 fit but untrained men, the study measured a significant performance improvement after taking 1,000mg of quercetin daily for 2 weeks, compared to placebo.5

More recently, a 2019 study evaluated quercetin’s benefits for muscle strength and resilience. Neuromuscular testing was used to assess the ability of quercetin to prevent strength loss and electromyographic changes that follows exercise. Twelve active men were randomly assigned to take 1,000mg of quercetin per day, or placebo, for 14 days. After a three-week washout period, they crossed over to the other treatment. The men taking quercetin showed a significant increase in maximum voluntary isometric contraction. Biochemical and functional indications of muscle damage were significantly lower in the quercetin group compared to placebo. For the first time, quercetin was demonstrated to enhance performance. The results showed that quercetin lessens the severity of muscle weakness caused by exercise, and reduces the symptoms of discomfort and strength loss that follow intense training.

However, quercetin is poorly absorbed, and improving its assimilation is essential to receiving the full benefits. Its bioavailability is low, and it can be a challenge to get an adequate amount into our tissues.

Two main factors can improve the absorption of quercetin: combining it with bromelain; and using phytosome technology.

Bromelain is a plant-based complex of protein-digesting enzymes originally found in pineapple, also known as proteases, that break down proteins into their constituent amino acids. Because it enhances absorption, bromelain helps to move quercetin from the digestive tract into the bloodstream. A clinically effective dose of bromelain enhances quercetin absorption, and it magnifies the efficacy of quercetin. Bromelain is also a highly effective anti-inflammatory in its own right. It can help to relieve joint and connective tissue pain for athletes, and reduce C-reactive protein, the inflammation marker.

Bromelain also directly supports athletic performance by facilitating protein assimilation. Protein is essential for tissue repair, muscle formation, and for every metabolic enzyme in the body. Bromelain frees up amino acids, the protein building blocks, so that they are better absorbed. Additionally, research confirms that bromelain induces the breakdown of stored fat, which provides steady energy for athletic activity.8

Phytosome technology is a method of combining a nutrient with other natural plant substances to greatly enhance absorption, and to protect the nutrient from breakdown by gut enzymes. Quercetin is even more effectively assimilated and brings greater benefits in a phytosome form, bonded to sunflower-sourced phospholipids. Because these phospholipids are also chief components of human cell membranes, the phytosome complex they form with quercetin is easily recognized by the body. In addition, quercetin absorption is boosted because this phospholipid phytosome complex is protected from destruction by digestive secretions and gut bacteria. The phytosome complex chaperones quercetin highly efficiently across the epithelial cell membrane barrier of the intestine into the bloodstream, so that greater amounts of quercetin reach the tissues, making quercetin much more available for cells to use.

In our clinic, many of our athletic patients take quercetin in a phytosome form with bromelain for improved performance. They notice better endurance and stamina, and reduced joint and muscle inflammation or pain. They report less frequent allergy or asthma symptoms, and better respiratory capacity. In addition, they like the ongoing protection against tissue degradation, and the potential benefits for the cardiovascular and nervous systems, and for maintaining youthful skin tone.

Recommendation: Quercetin 500mg in a sunflower phospholipid phytosome complex, with bromelain 200mg, taken once or twice daily, best between meals; or as directed by your healthcare provider.


  1. Nieman DC, Henson DA, Davis JM, et al. Quercetin ingestion does not alter cytokine changes in athletes competing in the Western States Endurance Run. J Interferon Cytokine Res. 2007;27(12):1003-1011.
  2. Davis, J. Mark, et al. “The dietary flavonoid quercetin increases VO2max and endurance capacity.” International journal of sport nutrition and exercise metabolism 20.1 (2010): 56-62.
  3. Nieman DC, Henson DA, Maxwell KR, et al. Effects of quercetin and EGCG on mitochondrial biogenesis and immunity. Med Sci Sports Exerc. 2009;41(7):1467-1475.
  4. Davis J.M, Murphy E.A, Carmichael M.D, Davis B. Quercetin increases brain and muscle mitochondrial biogenesis and exercise tolerance. Am. J. Physiol. Regul Integr. Comp. Physiol. 2009a;296:R1071–R1077.
  5. Nieman, D.C., Williams, A., Shanely, A., Jin, F., McAnulty, S.,Triplett, N.T., and Austin, M. (2010) Quercetin’s influence on exercise performance and mitochondrial biogenesis in untrained college students. Medicine and Science in Sports and Exercise.
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  8. Dave, Sandeep, et al. “Inhibition of adipogenesis and induction of apoptosis and lipolysis by stem bromelain in 3T3-L1 adipocytes.” PLoS One 7.1 (2012): e30831.