Energy drinks may provide a bit too much of a boost to your heart, creating additional strain on the organ and causing it to contract more rapidly than usual, German researchers report.

Healthy people who drank energy drinks high in caffeine and taurine experienced significantly increased heart contraction rates an hour later, according to research scheduled for presentation Monday at the annual meeting of the Radiological Society of North America, in Chicago.

The study raises concerns that energy drinks might be bad for the heart, particularly for people who already have heart disease, said Dr. Kim Williams, vice president of the American College of Cardiology.

"We know there are drugs that can improve the function of the heart, but in the long term they have a detrimental effect on the heart," said Williams, a cardiology professor at Wayne State University School of Medicine, in Detroit.

For example, adrenaline can make the heart race, but such overexertion can wear the heart muscle down, he said. There's also the possibility that a person could develop an irregular heartbeat.

From 2007 to 2011, the number of emergency room visits related to energy drinks nearly doubled in the United States, rising from slightly more than 10,000 to nearly 21,000, according to a meeting news release. Most of the cases involved young adults aged 18 to 25, followed by people aged 26 to 39.

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