Why Eating Lots of Apples Is Kind of Like Exercising

Substance found in red onions and apples seems to boost endurance, but don’t throw away your gym shorts yet.

June 24, 2009

A substance in berries may give you energy--but you'll have to eat more than one.

RODALE NEWS, EMMAUS, PA—Researchers have found that quercetin, an antioxidant available as a supplement and also found in certain vegetables and fruits, increased people’s endurance and boosted their aerobic capacity, even if they weren't exercising. The results are published today in the peer-reviewed journal International Journal of Sport Nutrition and Exercise Metabolism.


THE DETAILS: Quercetin, a natural polyphenolic flavonoid found in many food plants, particularly red onions, berries, and red apples, has been show in many in vitro and animal studies to boost performance, which is why it is often a favorite of elite athletes. But in the new small study, which involved 12 healthy, college-age volunteers who weren’t high-level athletes or regular exercisers, researchers found the supplement provided some benefits generally associated with exercise. After splitting the group, with one half taking 1,000 milligrams (mg) of the supplement for seven days and the other taking a placebo, researchers found that those taking the supplement could ride a bike 13 percent longer before they felt tired. That group also experienced a nearly 4 percent increase in VO2max, a typical measure of fitness. Should these results hold true in the real world, they could be widely beneficial, says lead researcher J. Mark Davis, PhD, professor and director of the exercise biochemistry laboratory at South Carolina University in Columbia. “How many people do you hear say they don’t have enough energy to continue through their day at work, or to do recreational things when they’re done work? The whole idea of having more endurance doesn’t necessarily just apply to athletes,” he says.

The study was partially funded by the Department of Defense, and funding for follow-up studies will come from the Defense Advanced Research Projects Agency and the National Institutes of Health.

WHAT IT MEANS: Not so fast—before you throw away your running shoes and dumbbells, understand that this is not a replacement for exercise. “I never would want people to think that this is a magic exercise pill,” says Davis. “It appears it can provide some benefits that exercise does, but a pill can’t provide it all the benefits for performance and health. But it’s a nice addition.”

For now, here’s what you need to know about this quercetin:

• Try it in food. Quercetin is found in many fruits and vegetables, but not in levels high enough to compare to the 500 mg/twice a day amount used in the study. A large red apple, for example, contains about 10 mg, so you’d have to eat 100 of them a day. But you can add more quercetin-rich foods to your diet; along with the examples above, these include grapefruits and leafy greens. Even if a lower amount doesn’t have the same effect on endurance, you’ll gain the other healthy benefits of these fruits and vegetables.

• Be smart about supplements. Since this is the first human study of its kind, researchers aren’t sure about many aspects of quercetin’s potential benefits on performance and health. Including, to name a few, the optimal dose and timing of the supplement, whether it’s better to take it by itself or in combination with other foods/supplements, whether it works in all people of all ages, and even exactly how it works. Davis says there are lots of quercetin-containing supplements out there, and some are mixed with all sorts of herbs and other supplements. He suggests looking for straight quercetin, and make sure it carries the QU995 trademark on the label, which means it’s more than 99 percent pure. The U.S. Food and Drug Administration recognizes quercetin as generally safe, and the agency is even reviewing the supplement for use as a food additive. Davis doesn’t recommend children take the supplement, but says many peer-reviewed studies have found it to be safe for adults in the amount used in the study. If you’re pregnant, or trying to conceive, talk to your doctor before trying quercetin.