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Quercetin Fights Flu

Sep 05, 2008

Mice given Quercetin, a naturally occurring substance found in small amounts in healthy fruits and vegetables including garlic, blueberries, green tea, broccoli and red wine, were less likely to contract the flu. The study also found that stressful exercise increased the susceptibility of mice to the flu, but Quercetin canceled out that negative effect. 
Quercetin, a Catechin flavonoid has been shown to have anti-viral properties in cell culture experiments and animal studies, with this the first study specifically looking at the flu. 
The study was carried out at the University of South Carolina and at Clemson University. 

The study was conducted using mice, but if Quercetin provides a similar benefit for humans, it could help endurance athletes, soldiers and others undergoing difficult training regimens, as well as people under psychological stress, according to Davis. 
Earlier mouse studies have found that stressful exercise can increase susceptibility to upper respiratory infections. There was also preliminary information that mice may be more susceptible to the flu when they exercise to fatigue. The researchers in the current study hypothesized that exercise would increase the chance of the mice getting the flu but that Quercetin would counteract the increased risk. 

The scientists examined four groups of mice. Two groups performed three consecutive days of running to fatigue on a treadmill to mimic a short period of stressful exercise. One group of runners received Quercetin, the other did not. The remaining two groups did not exercise. One non-exercise group received Quercetin while the other did not. All four groups were then exposed to a common bird flu virus, H1N1. 

The researchers found that: 

  • Stressful exercise increased susceptibility to the flu 
  • The mice that exercised developed the flu much sooner than those that did not 
  • Mice that exercised and took Quercetin developed the flu only as often as those that did not exercise.

Although this study was done with mice, a recent human study found that people who took Quercetin suffered fewer illnesses following three days of exhaustive exercise compared to those who did not. Unlike the mouse study, the humans were not inoculated with a virus. The study appears in the current issue of the American Journal of Physiology-Regulatory, Integrative and Comparative Physiology.