The tremendous growth in sales of energy drinks -- half of which are consumed by young adults or children -- has prompted a backlash from U.S. pediatricians and public health leaders. The latest warning, published Monday in the journal Pediatrics, concludes that energy drinks at best fail to live up to their hype and at worst present risks to children with heart conditions and other health problems.
Study authors from the University of Miami asked pediatricians "to be aware of the possible effects of energy drinks in vulnerable populations and screen for consumption to educate families."
Energy drinks are classified as dietary supplements, exempting them from federal limits on caffeine content that apply to sodas, the study noted. Energy drinks contain 75 to 400 milligrams of caffeine -- more than a can of Mountain Dew, at 54 milligrams, and potentially more than a tall cup of Starbucks coffee. While they boast natural stimulants such as taurine and guarana, doctors said their effects are unproven.
"What you're feeling is the caffeine and the sugar," said Dr. William Roberts, a sports medicine specialist at the University of Minnesota, who wasn't involved with the study. "I look at them as being more in the range of three to five cups of coffee, which is more stimulation than you need."
Young adults interviewed by the Star Tribune said they have tried energy drinks to stay up later, study longer and gain an edge in sports. Some said the benefits outweighed the bad taste of some brands, which drinkers described as cough syrup or "sour Mountain Dew."
"That to me is how effective the energy drink industry is at marketing," said Dr. Nimi Singh, who directs adolescent health and medicine at the University of Minnesota. "They're saying ... that you're going to get such a great result in your body that you can go ahead and drink this thing that almost tastes like medicine."
At least one study has reported a rise in drunken young adults in emergency rooms, because energy drinks make them feel more alert than they really are, Singh said.
In discouraging youth consumption, the Pediatrics study is taking on the prime market for energy drinks, which include Red Bull, Monster, Rockstar and Full Throttle. The beverages sell for $2 to $4.
Red Bull has advertised to teens through alignment with extreme sports and athletes such as snowboarder Shaun White, skier Lindsey Vonn and pitcher Tim Lincecum.
Responding to the Pediatrics study, the American Beverage Association said last week that risks from energy drinks are no greater than those from other beverages, and that coffeehouse coffee contains more caffeine.
Federal surveys have shown that teens get more caffeine from soda, tea or coffee than energy drinks, added the association's Dr. Maureen Storey.
The prospect that energy drinks improve athletic performance is another draw for young people. Regimented caffeine can boost endurance and short-term athletic performance, Roberts said -- but it can also make athletes too jittery.
In a letter to athletes on behalf of the Minnesota State High School League, Roberts wrote: "Energy drinks seem to reduce performance for technical skills that rely on timing and coordination; not attributes that help most athletes."
While Virginia banned energy drinks at high school sports, the Minnesota league stopped short of such action. "It's hard to ban something unless you're really willing to step in" and force violators to miss games, Roberts said.
Health officials are concerned enough that the nation's poison control centers are tracking caffeine overdoses related to energy drinks. In 2011, the centers have reported 331 incidents. More than half involved children and teens. One in five involved elevated heart rates. Forty-six had major or moderate effects.
Singh agreed that any source of excess caffeine can cause hypertension and other problems for children. She thinks energy drink companies deserve scrutiny because of their youth marketing.
"We really don't want our teenagers drinking tons of coffee per day," she said, "but to me the issue is that (energy drink makers) are targeting youth and making these unscientific claims about the other ingredients that they throw in."