Two cans of energy drink a day can have negative effects on the heart, study finds

A clinical trial, led by researchers at the University of the Pacific and David Grant Medical Center in the USA, has found that energy drinks can increase the risk of abnormal heart rhythms when consumed in quantities from two cans a day.

The researchers studied a group of young adults, aged between 18 and 40, among whom the drinks are particularly popular. Of the 27 volunteers, some were given two cans of energy drink while others were given the equivalent amount of a placebo drink once a day, every six days, for three weeks. Neither the participants nor the researchers knew who was given which drink until the end of the three-week trial.

Researchers measured the participants' heart rhythm and blood pressure before consuming the drinks, then four times during the six hours immediately afterwards.

The results showed an increase in a marker of abnormal heart rhythm risk, known as the QTc interval, in those given the energy drink. Visible on an electrocardiogram, this corresponds to the duration of a heartbeat and the time required for the heart's electrical system to recharge in preparation for the next heartbeat.

A slight increase in blood pressure was also observed compared to volunteers given the placebo. These effects persisted for two hours after the energy drinks were consumed.

The researchers recommend approaching such drinks with caution. At least 34 deaths potentially associated with energy drinks have been reported up to 2014 in the USA alone.