While energy drinks may get you all pepped up, consuming too much of it can increase your blood pressure and the risk of electrical disturbances in the heart, researchers suggest.
According to a recent study, drinking 32 ounces of an energy drink in a short time span may increase blood pressure and the risk of electrical disturbances in the heart, which affect heart rhythm.
As part of the study, researchers 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 measured the electrical activity of the volunteers' hearts by electrocardiogram, which records the way a heart is beating. They also recorded the participants' blood pressure. All measurements were taken at the study's start and every 30 minutes for 4 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.
These findings were published in the Journal of the American Heart Association.
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 6 milliseconds or 7.7 milliseconds higher at 4 hours compared to placebo drinkers. The QT interval is a measurement of the time it takes ventricles in the heart (the lower chambers) to prepare to generate a beat again. If this time interval is either too short or too long, it can cause the heart to beat abnormally. The resulting arrhythmia can be life-threatening.
The results of the study confirm previous findings and suggest that the QT interval changes are generally sustained over the four-hour monitoring period rather than being a short-lasting effect after consuming 32-ounces of an energy drink.
Researchers also found a statistically significant 4 to 5 mm Hg increase in systolic and diastolic blood pressure in participants who consumed the energy drinks.
"We found an association between consuming energy drinks and changes in QT intervals and blood pressure that cannot be attributed to caffeine. We urgently need to investigate the particular ingredient or combination of ingredients in different types of energy drinks that might explain the findings seen in our clinical trial," said lead author Sachin A. Shah, Pharm.D., professor of pharmacy practice at University of the Pacific, Thomas J. Long School of Pharmacy and Health Sciences in Stockton, California.