(Berkeley Wellness)

Quercetin: Food vs. Supplements
One of the most promising compounds in fruits and vegetables, quercetin is showing up in more and more supplements—including FRS, a widely advertised sports aid endorsed by Lance Armstrong.

Besides vitamins and minerals, plant foods are also rich in compounds known as phytochemicals, which may affect human health. One large group is the flavonoids, and among these, one of the most frequently studied is quercetin. Many fruits and vegetables are rich in quercetin; it is also found in black and green tea and red wine. Quercetin is an antioxidant and has anti-inflammatory effects. If an apple a day keeps the doctor away, perhaps it’s because it is rich in quercetin.

Quercetin—in foods and supplements—has been under study for its potential health benefits. It’s claimed that it helps prevent or treat heart disease, allergic reactions, asthma, arthritis, cancer, and prostate problems. As a sports supplement, it is supposed to improve performance, prevent fatigue, reduce recovery time, and boost energy.

What the studies show—or don't show
Findings about quercetin, while sometimes encouraging, have been inconsistent. In 2003, for instance, researchers at the Linus Pauling Institute in Oregon found quercetin to be a powerful antioxidant in the test tube, but they could not establish any measurable benefits in humans. Though the anticancer benefits of flavonoids, including quercetin, have been seen in lab studies, it is difficult to assess which flavonoids are best. They may work better in groups, not as single compounds. So far, there’s no evidence that quercetin on its own has an anticancer effect in humans.

The evidence about quercetin’s effect on exercise performance has also been mixed. Many of the claims are based more on speculation than on science. In some small studies, high doses of quercetin reduced colds and boosted alertness in athletes. But a well-designed 2009 study from the University of Georgia, which looked at 30 young men who did cycling tests before and after taking high doses of quercetin or a placebo, found that quercetin was no better than the placebo at enhancing performance, boosting energy, or reducing fatigue.

Bottom line: We don’t recommend quercetin supplements—the research is too limited. And their long-term safety is unknown. However, in foods, quercetin may have some value, and in any event it comes in wonderful packages. If it has health benefits, it’s probably as a team player. If you eat a varied diet that emphasizes fruits and vegetables, you’ll get a lot of quercetin. It may be one of the substances that make red wine a heart-healthy drink.

(I have never heard of this. There is so much to be discovered and learn!)