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New study links energy drinks to more heart, blood pressure changes than only caffeine

Apr 26, 2017

Sachin A. Shah, PharmD, associate professor of pharmacy practice at the Thomas J. Long School of Pharmacy and Health Sciences; Emily A. Fletcher, PharmD, deputy pharmacy flight commander; and their team at Travis Air Force Base have found that consuming energy drinks is linked to more change in heart rate and blood pressure than drinks containing only caffeine.

“We decided to study energy drinks’ potential heart health impact, because previous research has shown 75 percent of the base’s military personnel have consumed an energy drink,” Fletcher said. “Nearly 15 percent of military personnel, in general, drink three cans a day when deployed, which is more than we studied here.”

The study was, co-authored by Carolyn S Lacey, MD; Melenie Aaron; Mark Kolasa, MD; and Andrew Occiano ’16, PharmD. Titled “Randomized Controlled Trial of High-Volume Energy Drink Versus Caffeine Consumption on ECG and Hemodynamic Parameters,” it has been published online in the Journal of the American Heart Association.

Currently, there are more than 500 energy drinks on the market. The U.S. Food and Drug Administration generally considers caffeine doses of less than 40 milligrams as safe, however, energy drinks often consist of proprietary blends of ingredients in addition to caffeine. Health care professionals have observed a sharp increase in the number of emergency room visits and deaths associated with energy drink consumption.

“I have spoken to families that have been affected and that is my driving factor in researching the safe and efficacious use of energy drinks,” Shah said.

In the study, 18 participants were divided into two groups. One group was given 32 ounces of an energy drink that is available commercially and which contained 108 grams of sugar and 320 milligrams of caffeine. The control group was given a drink consisting of 320 milligrams of caffeine, 40 milliliters of lime juice and 140 milliliters of cherry syrup in carbonated water. The following week the researchers switched the drinks given to the two groups.

Using an electrocardiogram, the researchers measured the electrical activity of the heart of the participants. Shah, Fletcher and their team also measured the participants’ peripheral and central blood pressures before consumption and at several intervals during the 24 hours after consumption.

“Peripheral blood pressure is the measurement of the pressure in an outlying artery, typically an upper arm,” Fletcher said. “Central blood pressure is the measurement of the pressure in the aorta near the heart. Blood pressures at each location are not always affected equally when a substance is introduced, such as medications. Central blood pressure is an emerging and potentially superior method to assess health outcomes related to elevated blood pressure.”

“The QT interval is the measurement of the time it takes ventricles in the heart, the lower chambers, to repolarize, or prepare to generate a beat again,” Fletcher said. “It’s the pause from the end of the electrical impulse generating the heart to beat to the next impulse. If this time interval, which is measured in milliseconds, is either too short or too long, it can cause the heart to beat abnormally. The resulting arrhythmia can be life threatening.”

In the study, compared to the caffeine-only group, those in the energy drink group had a corrected QT interval 10-milliseconds higher at two hours. Fletcher explains that medications which affect the corrected QT interval by 6 milliseconds are required to have warning labels which state this effect.

Both the energy drink group and caffeine-only control group had increases in systolic blood pressure. After six hours, the systolic pressure of the control group had returned to close to the original level.

“On the other hand, those who consumed the energy drinks still had a mildly elevated blood pressure after six hours,” Fletcher said. “This suggests that ingredients other than caffeine may have some blood pressure altering effects, but this needs further evaluation.” Fletcher emphasizes that further research is needed to understand the risks of energy drink consumption: “This is a small study and further studies are needed to confirm these results.”

“This study validates some of our previous work at University of the Pacific, but questions remain regarding the ingredients that may be causing these changes,” Shah said. He was the primary investigator for the study entitled “Electrocardiographic and blood pressure effects of energy drinks and Panax ginseng in healthy volunteers: A randomized clinical trial,” which was published in the International Journal of Cardiology on Sept. 1, 2016.

Based on these preliminary findings, individuals who have high blood pressure, underlying cardiac conditions or other health issues may want to avoid or use caution when consuming energy drinks until more is known about their impact on heart health. Shah added, “Don’t blindly follow the buzz.”

By Anne Marie H. Bergthold