Health experts are sounding the alarm over the possible effects on young athletes of popular energy drinks such as Red Bull, the leading brand in a growing market.

High school and college athletes are increasingly consuming large quantities of these caffeine-loaded drinks to boost athletic performance or lose weight, said a dozen health experts at the SUNY Youth Sports Institute's first national symposium on energy drinks here this week.

But athletes who consume too many energy drinks could suffer from dehydration, tremors, heat stroke and heart attacks, the experts warned. Instead, they say, teen and adolescent athletes should drink water while training and playing - especially during hot and humid summer months.

Some experts called for the U.S. Food and Drug Administration - which treats energy drinks as dietary supplements - to require warning labels on the hundreds of energy drinks now on the market.

FDA spokeswoman Susan Cruzan said Wednesday the agency does not have the authority to do that.

"We have no guidance or regulations that govern the formulation of energy drinks," Cruzan said in an e-mail. "Under current law, the manufacturer is responsible for ensuring that its products are safe and such products do not require FDA premarket review or approval."

Researchers at Johns Hopkins University are currently seeking interviews with children and adolescents 8 to 21 years old who have become sick or experienced unpleasant aftereffects from energy drinks.

"There's a tremendous amount of caffeine in these drinks," Jeanna Marraffa, a clinical toxicologist at the Upstate New York Poison Center told USA TODAY during the conference on Tuesday. "I would say: know what's in these products, have a sense of how much you're consuming and realize they are not safe. Certainly you can have toxic effects from them."

Kathleen Miller, a research scientist at the University at Buffalo's Research Institute on Addictions, said the bitter orange found in some energy drinks is "very closely related" to ephedra. Due to a number of deaths, the FDA banned the sale of ephedra-containing dietary supplements in 2004.

"In most energy drinks, they're relatively small quantities so they're probably not doing any harm. But we really don't know," Miller said. "And there's no requirement whatsoever for the manufactures to moderate the amount that they're putting in."

Eric Small of the Mount Sinai Medical Center in Manhattan told of treating a 17-year-old female runner suffering from chest pains and fatigue. She collapsed at the finish line of one race and was rushed to an emergency room. Turns out she liked to skip breakfast in favor of drinking two or three cans of Red Bull each morning, Small says. More youngsters are substituting protein bars and shakes for real food, he adds.

"They think being lighter and eating less and drinking less will improve their performance," Small says.

Kate Zanot, a track and field coach at Harrison High School in Westchester County, N.Y., who attended the conference, said many students don't know the difference between energy drinks such as Red Bull and sports drinks such as Gatorade, so they consume the drinks interchangeably.

"It's a huge concern," she says.

Patrice Radden, a spokeswoman for Red Bull, said via e-mail Wednesday the company is confident in the safety of its products and does not see the need for warning labels.

"Red Bull is a functional drink and not a thirst quencher or hydrator," she wrote. "Red Bull encourages people who are engaged in a sport or other physical activity and drinking Red Bull to drink lots of water before, during and after the activity."

Rebecca Chang, a Columbia University graduate student attending the symposium, says the federal government should do more to regulate energy drinks. But, she notes, thrill- or edge-seeking athletes in their teens and 20s might be more attracted to the drinks if they have the added danger of a warning label.

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