A review of studies about the contents of energy beverages has raised serious questions about their efficacy and safety. The review, published in the November issue of the Mayo Clinic Proceedings, noted that the drinks contain high levels of caffeine and could pose dangerous, even life threatening effects on blood pressure, heart rate and brain function to some susceptible individuals.

The study found four documented cases of caffeine-associated death and five separate cases of seizures associated with consumption of energy/power drinks. Other reports included: (1) an otherwise healthy 28-year-old man who suffered a cardiac arrest after a day of motocross racing; (2) a healthy 18-year-old man who died playing basketball after drinking two cans of Red Bull; and (3) four cases of mania experienced by individuals known to have bipolar disorder.