Study findings as of 2015 show that energy drinks raise the blood pressure and the norepinephrine levels of young adults, and they prevent the decline in liver glycogen. Norepinephrine is a stress hormone chemical, and at elevated levels, it causes otherwise healthy individuals to have a higher risk of cardiac events.
The 2015 Mayo Clinic double-blind study gave 25 participants one 16-ounce Rockstar energy drink or a placebo that matched in both consistency and taste but had no caffeine or other stimulants. Participants were non-smokers, in good health and had an average age of 29. The norepinephrine levels of participants who drank the energy drink increased by over 73 percent compared to the placebo group that increased by 31 percent. Systolic blood pressure increased six percent in the Rockstar group, while the placebo group increased three percent.
A study done by researchers at the University of Bath in the United Kingdom found that long-distance cyclists performed just as well or better after drinking sugar water than those who drank energy drinks. This study gave participants sucrose- and glucose-based drinks. It was found that the sucrose absorbed faster in the stomach. Glucose, the main stimulant in many energy drinks, absorbed slower and led to stomach discomfort. Both sucrose and glucose prevented fatigue due to the decline in liver glycogen.