Doctors are studying a promising substance found in many common foods for its ability to fight or even prevent disease.

It's called FRS, that stands for Fights fatigue, Raises metabolism, Supports immune system. The drink's spokesman is champion cyclist and testicular cancer survivor, Lance Armstrong. He touts the drink's energy boost in an internet endorsement.

But it's the drink's key ingredient 'quercetin' that's got doctors buzzing.

"It looks like it reduces inflammation in the body and that in turn may help the body fight disease," says Dr. Georgia Robins Sadler.

Diseases like cancer. Quercetin is found in many foods like onions, blueberries, tea and apple skin.

In fact, Dr. Georgia Robins Sadler, president of the California American Cancer Society, says there may be some truth to that old wives tale:

“You go back to the old saying 'an apple a day keeps the doctor away.' something clued people in to create that saying," says Dr. Sadler.

Animal studies suggest quercetin has a beneficial effect on cells, helping the body stay healthier and fight disease.

"I think at this point you're seeing some excitement because in the laboratory, in animal studies, we're starting to see some promising results," says Dr. Sadler.

Still, Dr. Saddler says the key will be when the tests move to clinical trials, testing humans with the hope of achieving similar results.

Until then, we won’t know if and how much quercetin is effective.

Dr. Sadler says for now, the best thing to do is eat a well rounded diet, including foods that contain the promising compound.

"Eat yourself silly on fruits and vegetables and you won't do any harm" says Dr. Sadler.

As for FRS 'healthy energy' having cancer curing potential, Dr. Sadler says it's too soon to tell.

She'll wait until research reveals a more comprehensive conclusion.

"I’ll be the first on the band wagon if it looks like it works," says Dr. Sadler.

You can buy quercetin over the counter as a dietary supplement. But keep in mind, at this time there is no recommended dose.