Consuming too many energy drinks in a short timespan may increase blood pressure and disrupt heart rhythm, a study has found.
For the study, published in the Journal of the American Heart Association, enrolled 34 healthy volunteers between the ages of 18 and 40 years.
Participants were randomly assigned to drink 32 ounces of one of two commercially available caffeinated energy drinks or a placebo drink on three separate days.
The drinks were consumed within a 60-minute period but no faster than one 16-ounce bottle in 30 minutes.
Researchers at the University of the Pacific in the US measured the electrical activity of the volunteers’ hearts by electrocardiogram, which records the way a heart is beating. They also recorded participant’s blood pressure.
All measurements were taken at the study’s start and every 30 minutes for four hours after drink consumption.
Both energy beverages tested contained 304 to 320 milligrams of caffeine per 32 fluid ounces. Caffeine at doses under 400 milligrams is not expected to induce any electrocardiographic changes.
Other common ingredients in the energy drinks in the study included taurine (an amino acid), glucuronolactone (found in plants and connective tissues) and B-vitamins.
The placebo drink contained carbonated water, lime juice and cherry flavouring.
In participants who consumed either type of energy drink, researchers found that the QT interval was six milliseconds or 7.7 milliseconds higher at four hours compared to placebo drinkers.