Story by Merrie Schilterlowe on 09/20/2019TRAVIS AIR FORCE BASE, Calif. People with high blood pressure may want to limit, or lose their penchant for energy drinks, based on a new study published in the Journal of the American Heart Association.
The study shows energy drinks can abnormally impact the heart rhythm and raise blood pressure in people as young as 18 years of age.
"We think this is going to change people's understanding about the risks of energy drinks," said Dr. Sachin Shah, who leads pharmacy research and education at David Grant USAF Medical Center at Travis AFB.
The study has received national and international media coverage from network television stations, including NPR, the BBC and CBS.
In an interview with CBS, Shah said energy drinks can raise blood pressure by about four to five points in both systolic and diastolic blood pressure.
It's estimated that more than 30% of Americans ages 12 to 17 consume energy drinks on a regular basis. An earlier study found that nearly 45% of deployed military members consume at least one energy drink per day while 14% report drinking three or more daily.
Shah and his co-authors wanted to determine the impact energy drinks have on the heart and blood pressure since they have been linked to an increase in emergency room visits and deaths.
The researchers recruited 34 healthy 18- to 40-year olds at a university campus for the study, which is the largest controlled study to date. Volunteers were randomly assigned to drink 32 ounces of one of two commercially-sold caffeinated energy drinks or a placebo.
The energy drinks contained 320 to 340 milligrams of caffeine as well as taurine (an amino acid), glucuronolactone (found in plants and connective tissue) and B-vitamins. One of the drinks also included carnitine, guarana and panax ginseng. The placebo contained only carbonated water, lime juice and cherry flavoring.
Volunteers consumed the drinks in a 60-minute period, but not more than 16 ounces in 30 minutes, on three separate study days with a six-day wash out period in between.
Researchers used an electrocardiogram to chart the electrical activity in participants' hearts every 30 minutes over a four-hour period. They also measured their blood pressure.
They were specifically interested in changes in the QT interval a measurement of the time it takes the lower chambers in the heart to prepare to generate the next beat. If this time interval is either too short or too long, it can cause the heart to beat abnormally. The resulting arrhythmia can be life-threatening.
Test results showed that the QT interval was higher at about four hours for people who consumed the energy drinks than for those who drank the placebo. Also, both the top and bottom numbers in blood pressure measurement rose.
Shah published a similar study in 2017 involving 18 active-duty members in the same age groups who were randomly given either an energy drink or a beverage with 320 milligrams of caffeine, which equals about four cups of coffee.
The results showed that drinking 32 ounces of a commercially available energy drink increased the heart's electrical activity more than drinking the caffeinated beverage.
"In the first study, we didn't use a true placebo in the sense that it had caffeine in it," Shah said.
Although the researchers acknowledge that drinking 32 ounces of an energy drink may not be realistic, some brands come in 24-ounce cans making it possible for consumers to drink larger quantities.
"Aside from the fact that we are confirming findings from the previous study, we did a head-to-head trial where we looked at two different products," Shah said. "We were able to show that it's a class effect, not just one particular product.
Further study is needed to determine if it's one ingredient or a combination of ingredients in energy drinks that impact the heart and blood pressure, Shah said. The long-term effects of energy drinks are still unknown.