A clinical trial published in the International Journal of Sports Nutrition and Exercise Metabolism has shown that a phytonutrient found in certain spices, fruit and vegetables can help to boost endurance in athletes.

Clinical Trial

In a randomized, double-blind, placebo-controlled, crossover study a treatment group of unfit but healthy volunteers were given 500mg of quercetin to take twice daily. After 7 days both the active and placebo groups were asked to cycle until the point where fatigue would allow them to cycle no further.

The results showed that the group taking quercetin were able to continue cycling for over 13% longer than those taking the placebo. While this is the first clinical trial to study the endurance boosting effects of quercetin in humans, several previous animal and in vitro studies have indicated its potential benefits in this regard.

What is quercetin?

Quercetin is a natural flavonoid compound present in a variety of spices, fruits and vegetables. Onions and garlic are the spices containing the highest quantity of quercetin, while apples, grapes (wine too) and pears are fruits with high levels of this phytonutrient. Broccoli is the vegetable with the highest levels of quercetin and tea, which is getting so much good publicity these days, also contains high levels of this phytonutrient.

How quercetin boosts exercise endurance

Although there may be further reasons, we do know that quercetin's endurance enhancing effects are due primarily to its powerful antioxidant, anti-inflammatory, mitochondrial boosting properties.

• Anti-oxidant activity: When we exercise for long periods our cells release higher than normal quantities of potentially damaging free radical compounds. Although our body produces its own protective anti-oxidants their production may not keep pace with the vast number of free radicals released during endurance exercise. This applies even more so to those individuals who are unaccustomed to exercise.This is when dietary antioxidants such as quercetin are important as they help internal antioxidants such as superoxide dismutase, glutathione and others to deal with the increase in damaging free radical production.

• Anti-inflammatory activity: Important as exercise is, it is also a potent cause of inflammation in muscles, ligaments and other tissues; the longer the period of exercise, the greater the inflammatory response. Plant compounds such as quercetin help to modify excessive inflammation, reduce tissue damage and allow the athlete to continue to exercise for a longer period of time.

• Mitochondrial biogenesis: Mitochondria are the cellular components responsible for energy production. During exercise, as muscle and other cells work harder, they require more energy. Fortunately quercetin and other plant compounds have the ability to activate the signaling pathways that stimulate the formation of more mitochondria. More mitochondria mean more energy for the cell and that means that, if you take quercetin, you can exercise for longer.

Although the clinical studies used doses of quercetin that are higher than those found in most diets, if you eat spices and other foods that contain high levels of this compound you will benefit from its exercise enhancing and other health promoting effects. The alternative is to take a pure quercetin supplement or a supplement that contains this important phytonutrient

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