Energy drinks should carry warning labels about the amount of caffeine they contain, a team of scientists in the US has said.

Some energy drinks contained caffeine levels equivalent to drinking 14 cans of Coca-Cola, said the scientists, from John Hopkins University. Their comments appear in an article published in this month's Drug and Alcohol Dependency journal.

The energy drinks sector is one of the fastest growing in the US soft drinks market. The Hopkins team said the category was worth US$5.4bn.  

Roland Griffiths, lead scientist in the Hopkins team, said: "Without adequate, prominent labeling; consumers most likely won't realise whether they are getting a little or a lot of caffeine. It's like drinking a serving of an alcoholic beverage and not knowing if its beer or scotch."

The team claimed that because energy drinks were marketed as dietary supplements, the maximum level of 71mg per 12oz can for soft drinks did not apply in the eyes of regulators.

The American Beverage Association said today (24 September): "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 extreme names and caffeine content."

It said that forcing energy drinks to carry warning labels would create a "slippery slope", that would also have to extend to coffee.

The group added that a 16oz "regular coffeehouse coffee" contained around 320mg of caffeine, compared to 160mg in a similar-sized mainstream energy drink. Most firms marketed their energy drinks responsibly, it said. 

The Hopkins team said they had begun collecting "case reports of intoxication from energy drinks in children and adolescents".