Research by radiologists at the University of Bonn finds that caffeine in energy drinks has cardiovascular effects similar to those of caffeine in other beverages. That's not terribly surprising, but it is bound to be seen in a sinister light given the media-driven scare about these products, especially because one of the researchers incorrectly states that energy drinks contain more caffeine than coffee does. "The amount of caffeine is up to three times higher than in other caffeinated beverages like coffee or cola," said Jonas Dorner, who together with his collaborators presented the findings of a heart imaging study at a meeting of the Radiological Society of North America. "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."
The implication is pretty clear: Energy drinks pose a potentially deadly threat because they contain so much caffeine. Yet the drinks that Dorner and his colleagues gave their 18 subjects contained 32 milligrams of caffeine per 100 milliliters, compared to 76 milligrams per 100 milliliters for Starbucks coffee. So Starbucks coffee contains more than twice as much caffeine per milliliter as energy drinks, as opposed to one-third as much, as Dorner suggests. That's a pretty big mistake—and one that is likely to be repeated in future coverage of this issue because it jibes with the attention-grabbing claim that energy drinks are more dangerous than other caffeinated beverages.
In any event, the effects observed by Dorner and his colleagues are not very alarming:
Compared to the baseline images, results of cardiac MRI performed one hour after the study participants consumed the energy drink revealed significantly increased peak strain and peak systolic strain rates (measurements for contractility) in the left ventricle of the heart. The heart's left ventricle receives oxygenated blood from the lungs and pumps it to the aorta, which distributes it throughout the rest of the body.
"We don't know exactly how or if this greater contractility of the heart impacts daily activities or athletic performance," Dr. Dorner said. "We need additional studies to understand this mechanism and to determine how long the effect of the energy drink lasts."
The researchers found no significant differences in heart rate, blood pressure or the amount of blood ejected from the left ventricle of the heart between the volunteers' baseline and second MRI exams.
"We've shown that energy drink consumption has a short-term impact on cardiac contractility," Dr. Dorner said. "Further studies are needed to evaluate the impact of long-term energy drink consumption and the effect of such drinks on individuals with heart disease."
In other words, this study does not document any harmful or lasting effects from consuming energy drinks. And if caffeine poses a risk to people with heart disease, that risk presumably would be greater in the case of coffee, which supplies a bigger dose. If the caffeine in coffee does not scare you, there is no reason, aside from alarmist press coverage, why the caffeine in energy drinks should.