Consuming caffeinated energy drinks leads to a prolonged QT interval and an increase in blood pressure, according to a study of young volunteers who had their hearts tested after drinking either energy drinks or placebo.
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“Further investigation is warranted on whether an individual ingredient or a unique combination leads to the observed electrophysiological and hemodynamic changes,” wrote Sachin A. Shah of the University of the Pacific, Stockton, Calif., and coinvestigators. The study was published in the Journal of the American Heart Association.
To analyze electrocardiographic changes in the heart after consumption of 300 mg of caffeine plus other energy drink ingredients, the researchers assigned 34 healthy volunteers with an average age of 22 years to consume two 16-ounce bottles of either Drink A, a commercially available energy drink, Drink B, a different brand of energy drink, or a placebo drink for 3 days, followed by a 6-day washout period. Before and for 4 hours after consuming the beverages, volunteers had their hearts measured via ECG to test for differences in QT interval. Their blood pressures also were recorded.
Compared with placebo, the Drink A group had a 6.1 ms increase in QT interval and the Drink B group had a 7.7 ms rise. The maximum changes from baseline in corrected QT interval for Drink A, Drink B, and placebo were 17.9 ms, 19.6 ms, and 11.9 ms, respectively; both differences were statistically significant. Volunteers in Drink A and Drink B groups also had statistically significant increases of 5 mm Hg in systolic and 4 mm Hg in diastolic blood pressure after energy drink consumption, compared with placebo.
Both energy drinks used in the study contained caffeine (about 300 mg), taurine, glucuronolactone, and B vitamins. The investigators said that caffeine at doses under 400 mg is not expected to induce any electrocardiographic changes.
The coauthors noted their study’s limitations, including not investigating the effects of different doses and the possibility that consuming two 16-ounce bottles is an unrealistic real-world volume. That said, they noted that 16% of respondents to a 2,040-person survey admitted to consuming more than two energy drinks a day. In addition, though not every brand was tested, the researchers stated that, “the class of energy drinks, rather than one particular product, warrants use with caution.”
Dr. Shah reported serving as an expert witness in legal cases related to caffeinated energy drinks. The other authors reported no conflicts of interest.
SOURCE: Shah SA et al. J Am Heart Assoc. 2019 May 29.