A recent study from the University of Bonn in Germany showed more forceful heart contractions in students one hour after ingesting energy/caffeine drinks.
The amount of caffeine is up to three times higher than in other caffeinated beverages like coffee or cola. There are many side effects known to be associated with a high intake of caffeine, including rapid heart rate, palpitations, rise in blood pressure and, in the most severe cases, seizures or sudden death.
However, the research team advised that children and people with an irregular heartbeat should avoid the drinks.
These energy drinks can also interact with medications, especially those used in ADD, to cause unwanted cardiac side effects.