In rat studies, omega-3 fats, vitamin C, vitamin E, and green tea extracts have a synergistic effect on quercetin’s action. The Boone researchers used this information to design their next trials.
In July 2009, the Boone group described a trial utilizing a combination of quercetin, green tea, and fish oil. Quercetin (1,000 mg/day), with or without the addition of epicallocatechin 3–gallate (EGCG; 120 mg), isoquercetin (400 mg), and EPA-DHA (400 mg), was administered to a group of cyclists who went through the same 3-hour, 3-day period of extreme exertion. This time the treatment period lasted only 2 weeks. In this trial, the last dose was taken only 1 hour before the start of the heavy exertion. This trial yielded far better results: the mixture reduced post-exercise measures of inflammation, oxidative stress, and immune disruption. Plasma quercetin levels of those who took the supplement combination were almost twice as high as in those who took quercetin alone. This suggests that improved absorption was at least partly responsible for this improved effect.
Regular bouts of endurance exercise can increase mitochondrial density in muscle tissue by 50% in a period of weeks. In animals, similar increases in mitochondrial density can be triggered by caloric restriction, as well as by certain plant polyphenols, including isoflavones from soy, resveratrol, and EGCG. Quercetin has a similar effect, at least in mice.
In April 2009, Davis et al from the University of South Carolina reported that feeding mice 25 mg/kg of quercetin for a week almost doubled their muscle mitochondrial DNA. Feeding the mice even half that dose of quercetin increased their SIRT1 mRNA by 200% and increased their treadmill running time by 37%; however, repeating these experiments on humans yielded mixed results.
In December 2009 researchers had a study published looking for a similar effect in humans. Dumke and colleagues at the University of Montana recruited 40 cyclists, gave them either 1,000 mg/day of quercetin or placebo for 3 weeks, and then tested muscle biopsies from the riders. The researchers could not find any difference between those taking quercetin and those taking placebo in muscle efficiency, muscle mRNA expression, or other measurements.
Yet a study in 2006 had shown benefit. In this earlier paper researchers from Pepperdine University recruited 11 elite cyclists and fed them a mixture of antioxidant vitamins and green tea extract either with or without quercetin for 3 weeks. Those who received the mixture plus the quercetin improved their times on a 30-kilometer time trial by 1.7% more than those who didn’t receive the quercetin.
Of note, the Boone group’s 2009 study using athletes showed that quercetin, EGCG, and fish oil taken together decreased inflammatory markers, but did not produce changes indicative of increased mitochondria growth.