A new clinical trial published in the Journal of the American Heart Association reports that energy drinks can prolong QTc interval in ECG and raise blood pressure in volunteers.

Packed with caffeine and ingredients like guarana, taurine, ginseng, and B vitamins, these drinks promise to boost concentration, improve physical performance and reduce fatigue.

In the largest randomized, controlled clinical trial on the subject to date, researchers from the University of the Pacific in Stockton, California, along with collaborators from other institutions and led by Sachin A. Shah, a professor of pharmacy practice at the University of the Pacific identified how energy drink consumption affects the heart.

For the study, 34 adults aged 18 to 40 were enrolled. After an overnight fast, the volunteers consumed two 16-ounce bottles of either one of two energy drinks or a placebo, which contained carbonated water, lime juice and cherry flavoring. The study was double-blinded.

ECG and blood pressure readings were measured every 30 minutes for a total of 4 hours; a significant change in the QTc interval was observed.

A QTc interval of 450 milliseconds (ms) in men and 460 ms in women is considered the maximum for a healthy heart rhythm. Prolonged QT interval increases the risk of experiencing life-threatening arrhythmia and sudden cardiac death increases.

While consumption of the placebo drink caused a maximum change in QTc interval of an average of 11.9 ms, the two energy drinks resulted in average maximum changes of 17.9 ms and 19.6 ms. The researchers saw significant changes in the QTc interval length up to 4 hours after the volunteers had consumed the energy drinks. According to the FDA, QTc interval prolongation of over 10 ms prompts further investigations.

The researchers also found an average maximum change of 3.5 mmHg in diastolic BP and 4.6 to 6.1 mmHg in systolic BP when the study participants had consumed the energy drinks.

Caffeine in the energy drinks may have contributed to the change in blood pressure, but only to some extent. Other ingredients, particularly taurine, could also play a role.

None of the participants experienced QTc intervals over 500 ms. Clinically, a QT/QTc interval over 500 ms or a change over 30 ms warrants careful monitoring.

Dr KK Aggarwal

Padma Shri Awardee

President Elect Confederation of Medical Associations in Asia and Oceania   (CMAAO)

Group Editor-in-Chief IJCP Publications

President Heart Care Foundation of India

Past National President IMA