Too many energy drinks can trigger heart attacks, even in healthy people, according to scientists, who have warned parents to watch how much children consume.
Almost one in three 10 to 19-year-olds regularly consume the drinks, which often contain high levels of caffeine that can be bad for the heart.
They can also contain "hidden" caffeine in the form of "masking agents" such as guarana, which comes from a Brazilian plant and is identical to caffeine in coffee beans but twice as concentrated.
Adding guarana and other popular substances, such as ginseng and taurine, may generate "uncertain interactions", the researchers said.
Their work focused on the pharmacology of energy drinks (EDs) among children and young adults. The team also studied how the marketing of EDs as a means to relieve fatigue and improve physical performance may be ignoring real dangers.
The international research team based in Madrid, Spain, warned that energy drinks can trigger sudden cardiac deaths in young, apparently healthy individuals.