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17.12.2009

Stamina improves with one gram quercetin daily

Sports scientists at Appalachian State University have already told in posters, abstracts and press releases how they managed to increase the stamina of 26 untrained students by giving them a high dose of quercetin [structural formula shown below]. Their article will be published soon in Medicine & Science in Sports & Exercise.

In animal trials, quercetin increases the activity of the mitochondria, the cellular power packs. Studies on humans are less conclusive. In one on a dozen professional cyclists, quercetin supplements improved their 30 km times by 1.7 percent. However in a bigger study, also on cyclists, quercetin had no effect at all.

The researchers here decided to take their chances with untrained men because previous research had shown that quercetin imitates the effects of training on the muscle cells. Quercetin is therefore unlikely to add much to the muscle cells of a trained athlete, but the polyphenol might be able to add something to the muscle cells of untrained people. That was the researchers' line of reasoning.

The two dozen test subjects were given 1000 mg quercetin every day for two weeks. When the two weeks were up they had to cycle for an hour at 60 percent of their VO2max. That’s an intensity at which you can still just hold a conversation. After that the test subjects had to cycle for 12 minutes as fast as they could. After a period during which the quercetin was eliminated from the subjects' bodies, the researchers repeated the trial with a placebo. The figure below shows the test subjects' performances during the 12 minute time trial.

The performance effect of the supplement was 2.9 percent, according to the researchers. They describe this effect as noticeable, but small. The same goes for the effect on the mitochondria. The figure below shows the amount of mitochondrial DNA they found in the muscle cells of the test subjects.

All in all, the effects are disappointing, the researchers say. Perhaps you need to take quercetin for longer than two weeks if you want to see effects in humans. Or perhaps humans don't react so well to quercetin. "The aglycone form of quercetin was used in this study", the researchers write. "Future research may determine that the more bioavailable isoquercetin, as found naturally in onions and apples, has greater bioactive effects, especially when combined with other flavonoids and food components."

Source:
Med Sci Sports Exerc. 2009 Nov 13. [Epub ahead of print].

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