Energy drinks have sparked debate ever since hitting the market. The concoctions, usually consisting of sugar, caffeine, vitamins and several unregulated herbs, are marketed toward young people and may be landing some of them in emergency rooms. A recent study found that of all caffeine overdoses reported in 2007, 46 percent were in people under the age of 19.  And as many as 30-50 percent of teens and young adults consume energy drinks such as Monster, Rockstar, or Red Bull on a regular basis.

Even so, no regulations exist to control energy drinks, and some experts agree they’re fine in moderation. Others, however, say there is no safe level of energy drinks to consume.

So who’s right?

Perceived as a sports drink

A study published in January 2014 by the Centers for Disease Control and Prevention found that 20 percent of teens who enjoy energy drinks think they’re safe. An additional 13 percent view energy drinks as a type of sports drink. Energy drinks, however, have clear distinctions from sports drinks.

Sports drinks like Gatorade and Powerade are little more than flavored salt water, but they help replenish necessary electrolytes and water after a tough workout. Energy drinks do not hydrate—in fact, they tend to be dehydrating—and contain a number of potentially harmful ingredients.

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Still, teens and young adults perceive these drinks as being performance enhancers, either mental or physical. That may not be the case, says Dr. Ruth Litchfield, associate professor of food science and human nutrition at Iowa State University.

“Energy drinks typically contain stimulants, such as guarana, with caffeine-like effects, along with caffeine itself,” says Litchfield. Stimulants are substances that increase nervous activity, and elevate heart rate and blood pressure.

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Since they have this effect on the heart, too much can be a bad thing, leading to an elevated risk of heart disease, the nation’s No. 1 killer. Common energy drink components that act as stimulants include herbs such as guarana and ephedra, or ma huang. But in addition to these stimulants, many popular energy drinks have five times as much caffeine as a cup of coffee, Litchfield says.

Misleading labels

So what’s behind the misconception that these drinks can be good for you? “Some energy drinks may have a dietary supplements label rather than a nutrition facts label,” Litchfield says. By labeling a product a supplement, it takes on the positive air of a vitamin or fish oil pill in the eyes of many consumers.

“Dietary supplements are not regulated like food,” Litchfield adds—that means there are no restrictions on how many stimulants can be included in them.

Additionally, the labeling on energy drinks labeled as supplements is often inaccurate, a recent study found. “The bad news for consumers who actually

read product labels is that many of them are actually inaccurate,” says Neil Thanedar, analytical chemist and chief executive of LabDoor, the startup that performed the study.

LabDoor analyzed 25 popular energy drinks to see how closely ingredients matched labels. “The average caffeine claim is wrong by only 8 percent, but some vitamins see huge variances,” he said, though many brands do not disclose caffeine content levels, and aren’t required to.

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True vitamin content of these drinks ranges anywhere from 1 percent to 800 percent of what’s written on the label, Thanedar added. His team’s findings—that labels were far from accurate on vitamin levels—were corroborated by a similar study by Consumers Union, the advocacy and policy division of Consumer Reports. Following that study, Consumers Union put its support behind a Food and Drug Administration proposal to update labeling requirements.

But vitamin content isn’t what makes energy drinks potentially unsafe. Along with caffeine and other stimulants, many energy drinks contain an unhealthy amount of added sugar. The American Heart Association recommends a daily intake of no more than 6 teaspoons of added sugar per day for women, and 9 teaspoons for men. Many popular energy drinks contain more than 15 teaspoons of added sugars. Others contain aspartame or other artificial sweeteners.

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The resulting sugar rush adds to the burst of energy from the caffeine in energy drinks, but negative effects can last long after the high has faded. Too much sugar can result in Type II diabetes, obesity, and stress on internal organs from processing it.

Long-term overuse of caffeine can also be dangerous. Anxiety, nervousness and dehydration can occur in some individuals after just one drink. Those that consume energy drinks on a regular basis also risk caffeine toxicity, heart arrhythmias and cardiac arrest. To be safe, limit any caffeine consumption to less than two cups of coffee or tea per day, and drink plenty of water.

Lacie Glover writes for NerdWallet Health, a website that helps people reduce their medical bills.