Energy drinks may put some children and young adults at risk for serious health problems and should be regulated, say US researchers.
They reviewed scores of scientific studies on the health effects of energy drinks, which contain high levels of caffeine and other stimulants, and found cases of seizures, delusions, heart problems, and kidney or liver damage.
"Across the world, there are signs that for some people who consume these drinks, there are side effects," says Dr Steven Lipshultz of the University of Miami, whose study appears in the journal Pediatrics .
"The incidence is low," says Lipshultz, "but in certain groups that paediatricians care for, there may be higher risks."
Lipshultz's team is especially concerned about the effects on young adults and children, which account for half of the projected non-alcoholic energy drinks sales in the US. The report calls for regulatory action and more research.
Manufacturers claim their products enhance mental and physical performance. Red Bull's website, for instance, says the energy drink will increase concentration and reaction speed, and improve vigilance and emotional status.
But according to the Florida researchers, who reviewed the medical literature on the topic, the industry's claims of benefit are questionable.
Lipshultz and colleagues systematically searched studies and manufacturer websites for product information on energy drinks, which they defined as "beverages that contain caffeine, taurine, vitamins, herbal supplements and sugar or sweeteners and are marketed to improve energy, weight loss, stamina, athletic performance and concentration."
Mix of substances
They found the drinks have been linked with "serious adverse effects, especially in children, adolescents, and young adults with seizures, diabetes, cardiac abnormalities, or mood and behavioural disorders or those who take certain medications."
"We couldn't find any evidence at all of any therapeutic effects," says Lipshultz.
Caffeine is a particular worry, according to the team.
Of the more than 5000 US caffeine overdoses reported in 2007, 46 per cent occurred in youths aged 18 or younger.
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.
High doses of the herbal extract 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 said. "The problem is they contain a lot of other substances."
Until the effects of these drinks are clear, Lipshultz says young people with heart disease, seizures, diabetes, high blood pressure, or attention-deficit hyperactivity disorder should avoid the drinks.
Manufacturers downplayed the report.
"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," Red Bull said in an emailed statement.
Labelling and safety
Dr Scott Willoughby, a cardiovascular researcher at the University of Adelaide says the study highlights the lack of knowledge surrounding energy drinks.,
"There is in the medical literature reports of the benefits of these drinks, but also the lack of benefits that are touted," says Willoughby.
He says there needs to be more research into the effects of energy drinks, so that consumers and regulatory bodies are better equipped to make informed decisions.
A spokesperson from Food Standards Australia New Zealand (FSANZ) says energy drink sold in Australia must follow strict regulations, which limits the amount of caffeine to no more than 320 milligrams per litre - the equivalent of a cup of espresso coffee. The amount of added vitamins and other substances are also regulated.
"The label must say that the food contains caffeine and that it is not recommended for children; pregnant or lactating women; and individuals sensitive to caffeine," the spokesperson says. "It must also say 'consume no more than x cans or bottles a day' - the amount depends on the strength of the energy drink."