Already at least 31 percent of U.S. teenagers say they drink energy drinks, according to Simmons Research, no doubt because they're looking for the quick energy kick that the drinks provide. In the future, Report Buyers predicts that energy drinks will move beyond just energy and begin incorporating nutrition, taste, pain-killing and anti-aging ingredients into their products.

These drinks are heavily marketed to teens as a harmless way to boost energy, but in reality they've been linked to serious -- and widely unpublicized -- health effects. Among the top dangers are:

Energy drinks contain anywhere from 160 mg to 300 mg of caffeine, compared with 80 mg for a typical cup of coffee. While most adults can safely drink up to 200-300 mg of caffeine a day, many teens drink several energy drinks a day, sometimes in a short period of time.

Not surprisingly, a study by Johns Hopkins School of Medicine found that energy drinks can lead to caffeine intoxication, a condition that can cause nervousness, heart irregularities, increased blood pressure, insomnia, neurological symptoms and anxiety.

"The caffeine content of energy drinks varies over a 10-fold range, with some containing the equivalent of 14 cans of cola, yet the caffeine amounts are unlabeled and few include warnings about potential health risks of caffeine intoxication," the study's author said.

Energy drinks are commonly used as mixers for alcoholic drinks in bars and nightclubs, and there are now new pre-mixed alcoholic energy drinks on the market.

The dangerous combination of mixing energy drinks, a stimulant, with alcohol, a depressant, has proven deadly.

"It is scary to think that these energy drinks are being used as a mixer with vodka and whiskey," said David Pearson, a researcher in the Human Performance Laboratory at Ball State University. "You are just overloading the body with heavy stimulants and heavy depressants."

The resulting mix can lead to cardiopulmonary and cardiovascular failure.

Researchers from North Carolina's Wake Forest University revealed that mixing alcohol and energy drinks increases students' risk of harm.

After surveying over 4,000 U.S. students, they found that those who drank alcoholic energy drink cocktails were more likely to:

These harmful effects occurred because the energy drinks masked much of the alcohol's intoxicating effects, which allowed students to drink for longer periods.

Drinking two cans a day of an energy drink is enough to increase your blood pressure and heart rate, according Wayne State University researchers.

In a study of 15 healthy volunteers who drank two energy drinks a day for seven days:

The adverse effects were significant enough that the researchers recommended people with high blood pressure or heart disease avoid energy drinks.

5. Increased Risk of Substance Abuse

A study of college students found that those who consume energy drinks six or more days a month are three times as likely as those who don't drink energy drinks to smoke cigarettes or abuse prescription drugs. They're also twice as likely to use marijuana and have alcohol-related problems.

Energy drinks contain a lot of sugar (at least 7 teaspoons for each can) and high levels of caffeine that give teens a fast high, followed by a crash. The up-and-down jolt may lead some kids to reach for another can to get back up to their high point, leading to a dangerous cycle of dependence. Meanwhile, the more energy drinks consumed, the greater the risk of caffeine intoxication. It's even possible to experience side effects like rapid heartbeat and numbness and tingling in the hands and feet from the mega doses of vitamin supplements that some of the drinks contain.