NEW YORK (Reuters Health) - With Americans chugging energy drinks like never before, fears are growing among doctors that the ingredients might be putting some consumers at risk.
The beverages contain a hodgepodge of caffeine, sugar and dietary supplements such as vitamins and herbal extracts, whose effects aren't well understood.
In a new report out Monday, Florida pediatricians describe cases of seizures, delusions, heart problems and kidney or liver damage in people who had downed one or more non-alcoholic energy drinks -- including brands like Red Bull, Spike Shooter and Redline.
"Across the world there are signs that for some people who consume these drinks, there are side effects," said Dr. Steven E. Lipshultz, who heads the department of pediatrics at the University of Miami Leonard M. Miller School of Medicine.
"The incidence is low, but in certain groups that pediatricians care for there may be higher risks," he added.
The report, which calls for regulatory action and more research, comes only months after a U.S. crackdown on alcoholic caffeinated beverages such as Phusion Projects' Four Loko.
U.S. sales of non-alcoholic energy drinks are expected to hit $9 billion this year, with children and young adults accounting for half the market,
Because the beverages are classified as nutritional supplements, they have received much less scrutiny and are under fewer restrictions than both foods and drugs.
Manufacturers claim their products will enhance both mental and physical performance. Red Bull's website, for instance, says energy drink will increase concentration and reaction speed, and improve vigilance and emotional status.
"Red Bull's effects are appreciated throughout the world by top athletes, busy professionals, active students and drivers on long journeys," the website claims.
In 2010 alone, the company told Reuters Health, it sold in excess of 4 billion cans and bottles of the drink, which is now available in more than160 countries.
But according to the Florida researchers, who reviewed the medical literature on the topic, the industry's claims of benefit are questionable.
"We couldn't find any evidence at all of any therapeutic effects," Lipshultz said.
He began to take an interest in energy drinks a few years ago, when four kids from South Florida were brought to the hospital after swallowing a vitamin concoction their teacher had bottled.
"They all came in feeling tingling all over," Lipshultz said. "This prompted me to say, we've got to really learn about this."
What he and his colleagues found was a pile of anecdotes, but little hard evidence. In Ireland, for example, the country's poison center reported 17 cases of possible side effects between 1999 and 2005, including seizures, heart rhythm disturbances and two deaths.
And in New Zealand, 20 similar cases were reported between 2005 and 2009.
"It's the tip of the iceberg," Lipshultz ventured. "How many people take the time to call a poison control center when they don't feel well?"
While the U.S. poison control centers haven't been able to track potential side effects from energy drinks in the past, they have told Lipshultz they will start doing so from this year on.
Of course, isolated anecdotes don't prove the drinks are to blame. But they do have doctors wondering whether some people, kids in particular, might be at risk.
For example, caffeine is known to cause fast heart rate, insomnia, and anxiety, especially in sensitive individuals.
According to one study from New Zealand, just one energy drink is enough to make most kids experience some side effect, including mild ones like irritability or upset stomach.
And there are other ingredients with effects of their own, such as the amino acid taurine, the herbal extracts yohimbine, guarana and ginseng, and often loads of sugar.
High doses of yohimbine have been linked to increased blood pressure and heart rate. And like ginseng, yohimbine may interact with other drugs.
"If it were as simple as energy drinks just containing caffeine, that would be one thing," Lipshultz told Reuters Health. "The problem is they contain a lot of other substances."
What this all adds up to is still unclear. It's obvious that few people suffer serious side effects, but nobody knows just how common they are and who is likely to experience them.
"Many ingredients are understudied and not regulated," the Florida researchers write in the journal Pediatrics.
Lipshultz, for one, says people with heart disease, seizures, diabetes, high blood pressure, or attention-deficit hyperactivity disorder (ADHD) should think twice before downing an energy drink.
"Up until I did this review, I wasn't routinely asking my patients if they were drinking energy drinks," he told Reuters Health. "Now I am, and it is the basis for a discussion."
But manufacturers downplay the new report.
According to an e-mail from Red Bull, "This article just draws together material from the Internet and largely ignores in its conclusions the genuine, scientifically rigorous examination of energy drinks by reputable national authorities."
"The effects of caffeine are well-known and as an 8.4 oz can of Red Bull contains about the same amount of caffeine as a cup of coffee (80 mg), it should be treated accordingly."
The American Beverage Association, which represents several manufacturers, seconded Red Bull's criticism.
"Most mainstream energy drinks actually contain about half the caffeine of a similar size cup of coffeehouse coffee," it said in a statement. "In fact, young adults getting coffee from popular coffeehouses are getting about twice as much caffeine as they would from a similar size energy drink."
Lipshultz countered that he'd found caffeine contents ranging anywhere from 75 to 400 milligrams (mg) per container, including the small "energy shots."
Mild side effects begin to appear when people drink around 3 mg of caffeine per kilo body weight (1.4 mg per pound) in addition to normal dietary intake. That means an energy shot would push a typical 12-year-old three times over the limit.
And there is another difference between coffee and energy drinks, which are often marketed toward athletes.
"If you're a 16-year-old who just came out of football practice, you're not going to have three cups of hot coffee. But you might have three energy drinks," Lipshultz said.
In fact, high amounts of caffeine increase urine production, making our bodies lose water.
"If you are looking to prevent dehydration, sports drinks are what you should be drinking," Lipshultz said. Other experts recommend that tried and tested drink, water.
Concluded Lipshultz: "If there is no real upside to taking (energy drinks), and they clearly put some people at risk, my personal feeling is we should protect kids."
SOURCE: bit.ly/cxXOG Pediatrics, online February 14, 2011.