Many energy drinks are sold with messages that tell you they help during periods of mental stress. But it looks like combining Red Bull with mental stress is associated with increased blood pressure and a higher heart rate.
Researchers from the University of Fribourg in Switzerland looked at what happens when you drink Red Bull and have some mental stress. The had 20 people drink either 355 ml (12 ounces) of Red Bull or of water, wait 80 minutes, and then take a mental arithmetic test that lasted 5 minutes. The participants underwent continuous recordings of cardiovascular measurements and blood flow in the brain starting 20 minutes before the drink and up to 90 minutes afterward. The measurements included beat-to-beat blood pressure, heart rate, the volume of blood pumped with each beat, and the velocity of blood flow in the brain.
The researchers found that water had no significant effects on either the cardiovascular measurements or blood flow in the brain. But Red Bull increased both systolic and diastolic blood pressure by 7 mm Hg and 4 mm Hg, respectively, and heart rate went up by7 beats per minute. Systolic and diastolic blood pressure and heart rate went up further during the added mental stress of the arithmetic test after drinking Red Bull, with similar increases were also seen after drinking water. The combination of Red Bull and mental stress increased systolic and diastolic blood pressure by about 10 mm Hg and 7 mm Hg, respectively, and heart rate by 20 beats per minute, while blood flow velocity in the brain decreased.
Combining Red Bull and mental stress increases the amount of work that the cardiovascular system is doing and reduces cerebral blood flow during a mental challenge, the researchers concluded.
The study was published in the American Journal of Cardiology.