In 2007, just over ten thousand emergency room visits were attributed to energy drinks. However, this number had doubled by 2011, with more than twenty thousand emergency room visits reportedly connected to these liquid concoctions.

Even more concerning, middle-aged Americans are partaking in this trend. While the highest number of emergency room visits was seen in those between the ages 18 and 39, the biggest increase in overall numbers was seen in those forty and over, with an increase of 279 percent. (The numbers jumped from 1,382 reported emergency room visits in 2007 to more than 5,000 reported visits in 2011. That’s one heck of a leap.)

But just what makes these drinks so dangerous?

One of the biggest concerns of energy drinks is cardiovascular risk.  According to Live Science, one particular study concluded that drinking one (yes, just one) 16-ounce energy drink raised both blood pressure and a hormone called norepinephrine (a relative of adrenaline) in study subjects.

And that’s not all.

According to Seconds Count (SCAI), other studies have linked energy drinks to heart palpitations. In one such study, nearly 20 percent of college students who consumed energy drinks had heart palpitations.  

Perhaps one of the greatest reasons for this cardiovascular risk lies in the amount of caffeine that can be found in energy drinks. According to the Center for Science in the Public Interest, energy drinks can contain up to 357 milligrams of caffeine. However, that number differs based on the drink. For example, one 16-ounce Rockstar contains 160 mg of caffeine. But one Rockstar Citrus Punched contains 240 mg of caffeine.