In addition to alertness, energy drinks may also trigger abnormal heart rhythms and increased blood pressure. Researchers from the School of Pharmacy at the University of the Pacific, in Stockton, California, tested 27 healthy adults. The volunteers were split into three groups—one drank two cans of an energy drink per day, another consumed the same amount of a drink with Panax ginseng and the third a similar-tasting placebo beverage.

The subjects were given cardiovascular testing before and after the trial. After three weeks, the group imbibing the energy drinks had a significant increase in abnormal heart rhythms and higher blood pressure. The ginseng and placebo groups saw no change in their heart conditions.

Sachin A. Shah, a doctor of pharmacy and professor at Pacific’s School of Pharmacy and Health Sciences, says, “Our findings suggest that certain energy drinks may increase the risk of having an abnormal heart rhythm when consumed in high volumes. While we wait for more data, some consumers should exercise caution and not blindly follow the buzz.”

The Center for Science in Public Interest, a consumer health advocacy group, has reported that as of June 2014, 34 deaths have been associated with energy drinks.