We've heard these buzzy beverages are bad for us, but can't help but give in when an afternoon crash hits hard. The truth is, energy drinks are far more dangerous than your average cup (or three) of joe. In fact, the Drug Abuse Warning Network reports a sharp increase in the number of emergency visits as a result of consuming energy drinks, from 1,128 visits in 2005 to 13,114 visits in 2009.

"There is so much caffeine in these drinks that they can cause an arrhythmia, or abnormal heart rhythm," says Nicole Weinberg, M.D., cardiologist at Providence Saint John's Health Center in Santa Monica, California. "In rare and extreme cases, sudden death has been linked with excessive caffeine from these energy drinks."

From a medical standpoint, these energy-boosting beverages have little-to-no nutritional value -- they're loaded with as much as five times the amount of caffeine in one regular cup of coffee, a caffeine-containing plant called guarana, as much as 35 grams of sugar, as well as taurine, ginseng and some B vitamins which are thrown in for kicks. It's also worth noting that energy drinks are not regulated by the Food and Drug Administration (FDA), so there's more of a risk for negative side effects than almost anything else on the market, Dr. Weinberg notes.

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