Unless you’re a teen in England, energy drinks are easy to buy. But researchers are only starting understand how all the caffeine, sugar, and other ingredients affect your health. The results of a clinical trial published Tuesday provide a reason to be skeptical: the effect of an energy drink on one’s heart can last for hours, but it’s more than the oversized amount of caffeine that’s to blame.
Energy drinks aren’t your average beverage: Physician groups, including the American Academy of Pediatrics, note that “caffeine and other stimulant substances contained in energy drinks have no place in the diet of children and adolescents.”
Even for adults, high levels of energy drink use were liked with mental health issues in US Soldiers. The results of this recent trial, led by Sachin Shah, a doctor of pharmacy at the University of the Pacific, point to another reason to be wary of energy drinks.
Shah’s 34 participants drank 32 ounces of two “commercially available” energy drinks, and participants experienced high blood pressure and a change in the heart’s electrical signaling. Both can lead to bigger problems down the line. Shah published his results in the Journal of the American Heart Association.
“Our findings suggest that caffeinated energy drinks as a class should be consumed with caution and excessive consumption avoided,” Shah tells Inverse. He adds that the effects don’t come down to high caffeine content: “The combination of caffeine with other ingredients needs further exploration.”
How Energy Drinks Affect the Heart
To be fair, Shah’s participants drank a lot of energy drinks: They rotated between 32 ounces of two types of commercially available energy drinks and a placebo, which was carbonated water and cherry-lime flavoring.
When Shah and his team monitored their heart activity for up to four hours after each person drank their fill, he noticed an elongation in the heart’s QT interval, which is how long it takes to recharge the electrical impulses that allow it to beat. Even after drinking the placebos, the QT intervals were lengthened, but the energy drinks caused even greater elongations of the QT interval, from roughly 6 to 7.7 milliseconds longer than the changes seen in the placebo condition.
Those small elongations in heartbeat were accompanied by rises in blood pressure, but Shah explains that the changes in QT interval are particularly of concern. For one, these findings have been replicated over the course of several earlier studies, suggesting that there really are electrical consequences for consuming large amounts of energy drinks. These prolonged intervals, he notes, are a are “a marker on the EKG that indicates increased risk for triggering a potentially fatal arrhythmia.”
Don’t Just Blame Caffeine
As tempting as it is to chalk up the changes to caffeine, Shah explains that there actually wasn’t enough caffeine in the energy drinks to explain the effects he saw. “Our EKG findings can’t be explained by caffeine alone as normally, caffeine under 400mg has not been shown to impact the heart rhythm.” The drinks in his study contained between 302 and 340 mg of caffeine.
So what is actually driving the effects on electrical impulses? It probably comes down to the additional ingredients that are common in energy drinks. Specifically, the unnamed “commercially available” drinks in Shah’s study included taurine, glucuronolactone, B vitamins, and “other proprietary ingredients.”
Even more likely, it’s probably not even just one of these ingredients, but the combination of them.
In February, a study published in The Journal of Nutrition actually tested combinations of common energy drink additives (including taurine and glucuronolactone). Those authors also reported prolonged QT intervals in their participants’ hearts when they consumed traditional energy drinks. When they consumed drinks with only one component (just caffeine, or just taurine, for example), they didn’t see the same effects.
“So far, these effects caused by energy drinks cannot be explained by any of the tested components: caffeine, taurine, or glucuronolactone,” those authors wrote. Instead, they proposed the idea that a combination of these three ingredients could represent an “additive reaction”: In short, all three together create a health effect that’s greater than the sum of its parts.
Based on his results, Shah also argues that the additional ingredients make it unique, with effects (and potential harms) that make them more that just an alternative to coffee or soda.
“The totality of evidence suggests that the unique combination of ingredients in energy drinks has a different safety profile when compared to coffee and soda,” he adds.
Background: Energy drinks have been linked to an increase in emergency room visits and deaths. We aim to determine the impact of energy drinks on electrocardiographic and hemodynamic parameters in young healthy volunteers.
Methods and Results: A randomized, double‐masked, placebo‐controlled, crossover study was conducted in healthy volunteers. Participants consumed 32 oz of either energy drink A, energy drink B, or placebo within 60 minutes on 3 study days with a 6‐day washout period in between. The primary end point of QTc interval and secondary end points of QT interval, PR interval, QRS duration, heart rate, and brachial and central blood pressures were measured at baseline, and every 30 minutes for 240 minutes. A repeated‐measures 2‐way analysis of variance was performed with the main effects of intervention, time, and an interaction of intervention and time. Thirty‐four participants were included (age 22.1±3.0 years). The interaction term of intervention and time was statistically significant for Bazett’s corrected QT interval, Fridericia’s corrected QT interval, QT, PR, QRS duration, heart rate, systolic blood pressure, diastolic blood pressure, central systolic blood pressure, and central diastolic blood pressure (all P<0.001). The maximum change from baseline in Bazett’s corrected QT interval for drinks A, B, and placebo were +17.9±13.9, +19.6±15.8, and +11.9±11.1 ms, respectively (P=0.005 for ANOVA) (P=0.04 and <0.01, respectively compared with placebo). Peripheral and central systolic and diastolic blood pressure were statistically significantly different compared with placebo (all P<0.001).
Conclusion: Energy drinks significantly prolong the QTc interval and raise blood pressure.