The U.S. Food and Drug Administration said Monday it would investigate whether as many as five deaths may be linked to high-caffeine Monster Energy Drinks.
Amy Goodson, a registered dietitian for the Texas Health Ben Hogan Sports Medicine program in Fort Worth, said the drinks are loaded with so many stimulants that they can be dangerous.
"The biggest challenge with energy drinks is they contain a large amount of caffeine,” she said. “But in addition, they also contain other stimulants like ginseng ... that speed up the central nervous system. That, in combination with sugar, can be too much for the body."
Five months ago, 14-year-old Anais Fornier of Maryland drank two Monster Energy Drinks and then died of a heart attack, one of five similar cases nationwide.
An autopsy found she died of cardiac arrhythmia due to caffeine toxicity. Fornier had an inherited disorder than can weaken blood vessels. Her parents have filed a wrongful death lawsuit.
An FDA spokeswoman cautioned that there was no proof any deaths have been linked directly to the beverage.
Monster Energy issued a statement, strongly denying that two cans of the drink "by itself can cause a death by caffeine toxicity."
But there's no doubt they're loaded with stimulants.
The caffeine in two cans of Monster Energy Drink is the same as 14 12-ounce sodas -- five times what's recommended daily for teens and younger children.
Illinois Sen. Dick Durban asked the FDA to investigate after learning about what happened to the Maryland girl.
"She had a common heart condition,” he said. “It wasn't life-threatening. Thousands of people have it. But it turns out they were so packed with caffeine, it killed her."
Goodson said she welcomed the FDA scrutiny.
"It's definitely important that drinks like this be regulated and educate kids for the health risk it could be for them,” she said.
The Associated Press and NBC Chicago contributed to this report.