My 14 year old daughter, Anais, died from cardiac arrythmia due to caffeine toxicity, after ingesting these drinks. Not only have there been documented deaths, but there are more than 10,000 ER visits, each year, linked to the consumption of these drinks. Besides the high doses of caffeine, which can cause abnormal heart rhythms, high blood pressure, seizures, liver damage, and death, they can also contain unregulated herbal supplements, like guarana and yerba mate. U.S. sales of these drinks are expected to hit $9 billion this year, with children and young adults accounting for half the market.