A study by researchers at the University of South Carolina's Arnold School of Public Health, led by Dr Mark Davis, shows that quercetin, the powerful antioxidant/anti-inflammatory compound found in fruits and vegetables significantly boosts endurance capacity and ‘maximal oxygen capacity’ (VO2max) in healthy, active but untrained men and women. The findings of the study, one of the first in humans to examine the energy-boosting effects of quercetin, are reported in the International Journal of Sports Nutrition and Exercise Metabolism, June 09.

Dr Davis said the fatigue-fighting and health properties of quercetin (found in the skins of red apples, red onions, berries and grapes) have implications not only for athletes and soldiers whose energy and performance are tested to the extreme, but also for average adults who battle fatigue and stress daily. He said that quercetin’s ability to boost the immune system and increase mitochondria (the powerhouse of the cell) in muscle and brain could be great news for those who often think that they're too tired to exercise, inlcuding, maybe, those suffering from energy sapping conditions such as chronic fatigue syndrome.
For the study, half of 12 participants (healthy, relatively active, college-age students, not physically trained athletes or on a regular exercise training programme) were given 500 milligrams of quercetin twice a day in juice for seven days. The other subjects drank juice with placebos. After the seven days of treatment, during which the subjects were told not to alter their physical activity, the participants rode stationary bicycles to the point of fatigue.

Researchers also tested their additional VO2max, one of the most important measures of fitness. Then the participants received the opposite treatment for another seven days before riding the bicycle to the point of fatigue and VO2max tests. After taking quercetin for only seven days, the participants had a 13.2% increase in endurance and a 3.9% increase in VO2max – both statistically significant results which suggested that quercetin supplementation was able to mimic some of the effects of exercise training.

Although the study did not examine why the results were so dramatic, Davis said pre-clinical data suggest that quercetin may increase the mitochondria in brain and muscle cells. He likened the mitochondria to the
‘powerhouse of the cell’ producing most of its energy. Mitochondria in brain and muscle also are believed to be fundamentally important in age-related dementia, obesity, diabetes and cardiovascular dysfunction and mitochondria malfunction is believed by some to be a crucial factor in ME and CFS.

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First Published October 2009

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