They claim to "give you wings," "unleash the beast" and propel you to attack life at "full throttle," but the bevy of energy drinks on the market could provide more than a turbo-charged rush.
Researchers at the Johns Hopkins University say some of the wildly popular beverages contain potentially harmful levels of caffeine - as much as 14 cans of Coca-Cola. In a review article appearing in this month's issue of the journal Drug and Alcohol Dependence, the researchers say the drinks should carry warning labels displaying their caffeine content and possible health risks, such as nervousness, anxiety, insomnia, rapid heartbeat and tremors.
Caffeinated energy drinks are marketed as supplements, not soft drinks, and are not required to list their caffeine content or comply with the U.S. Food and Drug Administration's maximum caffeine content for soda and other beverages. In addition, they are actively marketed to teens and young adults, impressionable groups that may not be aware of the dangers, said Roland Griffiths, a professor of psychiatry and neuroscience at Johns Hopkins School of Medicine and one of the study's authors.
"I believe people should be informed about what they are taking and what the risk is," he said. "First and foremost, we need to label the amount of caffeine and label it prominently - not in fine print. At the very least, we should know how much caffeine is in the product, and we should have some indication of what the drug does."
The organization that represents the top-selling energy drinks said the products are not marketed to children but to young adults and argued that the researchers' study unfairly characterized all caffeinated energy beverages into one unfavorable depiction. These top-sellers, which include such brands as Red Bull and Monster Energy, account for 95 percent of energy drink sales, the group said.
"It's unfortunate that the authors of this article would attempt to lump all energy drinks together in a rhetorical attack when the facts of their review clearly distinguish the mainstream responsible players from novelty companies seeking attention and increased sales based solely on sensationalistic names and extreme caffeine content," Craig Stevens, a spokesman with the American Beverage Association, said in a statement.
Griffiths, who has been studying caffeine for more than two decades, said caffeine intoxication can, in rare cases, lead to death. His article is a review paper that compiles studies, reports and surveys on caffeine intake, chemical dependency and energy drinks from numerous sources. The article mentions cases of adverse reactions from caffeine in energy drinks reported to U.S. poison control centers.
"I'm not concerned about someone whose caffeinated beverage of choice is Red Bull - they really are no different than a coffee drinker at that point," he said. "But it's the sporadic use to people who are not tolerant and who are naive and vulnerable in other ways that make it problematic."
Griffiths notes that caffeine stimulant pills such as NoDoz, which contains between 100 and 200 milligrams of caffeine, include a warning on the label saying that too much caffeine may cause nervousness and irritability and that they should not be taken by children under 12.
An FDA spokeswoman said the federal agency has not had time to review the article and could not comment on its claims.
A spokeswoman with Red Bull's U.S. headquarters in Santa Monica said the company is "confident in the safety" of its product and notes that the FDA does not require the caffeine amount to be listed on the drink's label.
Stevens, the beverage association spokesman, noted that the "mainstream" energy drinks that his organization represents have about half the caffeine content found in an average serving of coffee. A 12- ounce cup of coffee contains about 200 milligrams of caffeine. An 8.3-ounce can of Red Bull has 80 milligrams.
"So those suggesting that energy drinks should require warning labels should be aware of the slippery slope this would create," he said. "To be consistent, products at coffeehouses also would require such unnecessary labeling."
Maureen Storey, senior vice president for science policy for the beverage group, said caffeine in such doses is safe.
Stephen Shorofsky, a professor of medicine at the University of Maryland Medical Center, said he thinks energy drinks are "generally safe," except for people with erratic heartbeats, or arrhythmias.
"Anything can cause toxicity," said Shorofsky, director of the electrophysiology laboratory at the medical center. "Is it safe to have caffeine? Sure it's safe to have caffeine. But can you get to a point, where you can cause harmful effects to yourself? Sure."
Still, Griffiths maintains that the burgeoning energy drink industry is a marketing machine whose products are different from a morning cup of coffee - and potentially dangerous.
Since the launch of Red Bull in Austria in 1987 and in the United States a decade later, the market for caffeinated energy beverages has expanded worldwide and accounts for a $5.4 billion industry, Griffiths said.
With names like Amp Energy, Rock Star, and No Fear, the products sell not only a beverage, but a high-energy lifestyle, with claims to expand strength, endurance and toughness. Red Bull says it can "improve vigilance," and the company sponsors competitions in extreme sports and motor cross.