(WSVN) - A new study says energy drinks are worse for your heart than caffeine alone.

Drinking 32 ounces of an energy drink is associated with potentially harmful changes in heart function and blood pressure, but other ingredients besides caffeine may be to blame, Reuters reports.

Most energy drinks contain caffeine in addition to other ingredients. Energy drink manufacturers claim their ingredients are as safe as caffeine; however, the increase in popularity of those drinks has grown alongside a significant rise in ER visits and deaths associated with them.

While the Food and Drug Administration says caffeine in doses up to 400 mg (the equivalent to five cups of coffee) is safe, the study in the Journal of the American Heart Association says little is known about the safety of other ingredients that are in those drinks.

Researchers compared physical changes in a group of 18 healthy men and women after they drank a commercially-available energy drink, and after drinking another drink with the same amount of caffeine but none of the other ingredients.

The energy drink tested contained 4 ounces of sugar, B vitamins, and an “energy blend” of taurine and other ingredients often found in drinks like Red Bull, 5-Hour Energy, and Monster Energy. The drink also contained 320 mg of caffeine, the same amount in approximately four cups of coffee.

In the study, researchers measured subjects’ blood pressure and used an electrocardiogram (or EKG) to measure heart activity for 24 hours after the participants consumed the beverages.

They found that a change in the EKG sometimes associated with life-threatening heartbeat irregularities was seen after the subjects had the energy drink, but not after they drank the beverage containing just caffeine. Researchers noted that several drugs have been taken off the market for causing the same effect.

The study also found that blood pressure increased by about 5 points after participants consumed the energy drink, but just under 1 point after having the caffeine drink. Blood pressure remained elevated 6 hours later, they said.

Authors of the study said such changes are not problematic for healthy individuals, but patients with heart conditions should use caution with energy drinks. They said they believed larger studies should be conducted to evaluate the safety of the non-caffeine ingredients in energy drinks.

“The energy drink industry claims that their products are safe because they have no more caffeine than a premium coffee house coffee,” said Dr. Jennifer L. Harris from University of Connecticut’s Rudd Center for Food Policy and Obesity in Storrs to Reuters, who wasn’t involved in the study.

“However, energy drinks also contain a proprietary ‘energy blend,’ which typically consists of stimulants and other additives. Some of these ingredients (including taurine and guarana) have not been FDA-approved as safe in the food supply, and few studies have tested the effects of caffeine consumption together with these ‘novelty’ ingredients,” she continued.

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