Quercetin: a magic bullet for ultradistance athletes?

Aerobic exercise causes oxidative stress. It's a natural occurence that results from by-products produced from oxidative processes that are necessary for aerobic metabolism. These by-products, sometimes referred to as "free radicals" or "reactive oxygen species" (ROS) are also created from the inflammatory responses to muscle injury resulting from prolonged, repetitive muscle activity. It's most evident in long distance runners whose muscles are activated eccentrically (producing force while being stretched, during the stepping phase of running).

The problem with ROS is that they are believed to instigate muscle injury and reduce immune function making some athletes more susceptible to infection. In fact, increased incidence of upper respiratory tract infection occurs in athletes during heavy training and competition. Those athletes who engage in prolonged intense exercise will experience a significant amount of oxidative stress, which can lead to muscle injury, increased fatigue and increased susceptibility to infection.

Bring on the antioxidants. Antioxidants, natural chemicals in the body, fight the ROS and do it quite effectively. There are many types of antioxidants but one type in particular is the group known as flavonols. Flavonols are thought to be anti-inflammatory, cardioprotective, anticarcinogenic and antioxidative. One flavonol getting more attention in endurance exercise research is quercetin, naturally found in foods such as onions, berries, red wine, broccoli, apples and tea. It's getting more attention as a supplement, often sold in a blend containing vitamin C (another antioxidant that enhances quercetins effects) and niacin (for it's blood flow enhancing capabilities). It is believe that quercetin supplementation can increase the body's antioxidant power and possibly reduce those negative effects from ROS. In fact, one group of investigators observed reduced upper respiratory tract infection among athletes consuming the supplement.

To test quercetin's effects on blood oxidative capacity in response to ultramarathon competition, Quindry et al from Appalachian State University in North Carolina tested several athletes competing in the 160-km Western States Endurance Race. Sixty three male and female athletes were recruited and placed into either a quercetin group or a placebo group. The study was a randomized and double-blinded. For three weeks, athletes in the treatment group consumed 1000 mg quercetin, 1000 mg vitamin C and 80 mg niacin daily. Blood was drawn prior to the race and during the first half hour following the race. The investigators tested the athletes for plasma antioxidant capacity, the first indication that quercetin is indeed decreassing exercise-induced oxidative stress.

What they found:

• Quercetin levels were 6.6-fold higher in the quercetin group compared to the placebo group
• Quercetin levels decreased significantly during the race in both groups
• Quercetin supplementation did not affect plasma antioxidant capacity
• Quercetin supplementation did not alter oxidative damage

Conclusion: this study did not find a protective effect from quercetin supplementation during ultramarathon running. So, is it worth the money to buy the supplements? Maybe, because some studies have noted positive effects.

Final word: Instead of supplements, why not get your quercetin from vegetables and fruits? A well balanced diet containing several daily servings of fruits and vegetables will more likely provide you all the antioxidant power (in addition to several other benefits) you require as an endurance athlete.

Reference: Quindry et al. Oral quercetin supplementation and blood oxidative capacity in response to ultramarathon competition. Int. J. Sport Nutr. Exerc. Metab. 18, 2008.