Caffeine cleared? Energy drinks’ heart effects may not be stimulant’s fault, says study

By Will Chu

- Last updated on GMT

©iStock/Mauro Matacchione
©iStock/Mauro Matacchione
The interaction of common ingredients contained in energy drinks may have a bigger say in the beverage’s effects on cardiovascular factors that affect the heart rhythm, a US study concludes.

A research team point to a blend of taurine, glucuronolactone and B-vitamins as possibly having a greater influence on the heart than fellow energy drink staple, caffeine, when consumed in excess.

"We found an association between consuming energy drinks and changes in QT intervals and blood pressure that cannot be attributed to caffeine,”​ said lead author Sachin Shah, professor of pharmacy practice at University of the Pacific in California.

“We urgently need to investigate the particular ingredient or combination of ingredients in different types of energy drinks that might explain the findings seen in our clinical trial."

The study tests two energy beverages that contained 304 to 320 milligrams (mg) of caffeine per 32 fluid ounces.

Professor Shah and colleagues point to evidence that found caffeine at doses under 400mg are not expected to induce any electrocardiographic changes.

Energy drink ingredients

Although commonly promoted as supplements that can boost performance and cognition, these drinks are linked to a number of side effects that are cardiovascular and neurological in nature.

Supplementation with taurine is also believed to induce an anti‐arrhythmic rather than pro‐arrhythmic effect,

However, as recently as 2015, the European Food Safety Authority (EFSA) repeatedly stated that it was unlikely that taurine interacts adversely with or enhances caffeine’s effects.  

Data on glucuronolactone and B‐vitamins is limited but are typically regarded as safe, although the researchers thought ingredients that may be safe individually may require further investigations when used in combination.

In December 2003, caffeine and ephedra‐containing supplements were withdrawn from market after the discovery of the supplements’ link to negative effects on the heart.

Study details

The University of the Pacific team asked 34 healthy volunteers to consume 32 ounces (oz) of either energy drink A, energy drink B, or placebo within 60 minutes on three study days with a six‐day washout period in between.

The team found that the QT interval, a measure of time taken for heart ventricles to generate another beat, was 6 milliseconds or 7.7 milliseconds higher at 4 hours compared to placebo drinkers. If this time interval is either too short or too long, it can cause the heart to beat abnormally.

The QT interval changes were generally sustained over the four-hour monitoring period rather than being a short-lasting effect after consuming 32-ounces of an energy drink.

Researchers also found a statistically significant 4 to 5 mm Hg increase in systolic and diastolic blood pressure in participants who consumed the energy drinks.

“Caffeinated energy drinks significantly prolong the QTc interval and raise brachial and central blood pressure post‐acute exposure,”​ the study concluded.

“Further investigation is warranted on whether an individual ingredient or a unique combination leads to the observed electrophysiological and hemodynamic changes. The impact of long‐term energy drinks consumption remains unknown.”

Commenting on the findings, Kate O'Dell, professor of pharmacy and director of experiential programs at the University said, "Energy drinks are readily accessible and commonly consumed by a large number of teens and young adults, including college students.

“Understanding how these drinks affect the heart is extremely important,"​ she added.  

Study limitations

The team noted the study's limitations, which included the study design set up to assess the effects of short-term consumption of an energy drink.

It did not provide insight into long-term effects nor the effects of routine energy drink consumption.

The study added that energy drink consumption was evaluated alone, and it was not uncommon for energy drinks to be consumed in combination with other substances such as alcohol.

The researchers also highlighted that the study included only healthy individuals between the ages of 18 to 40 years and the results may be different in other populations.

Source: Journal of the American Heart Association

Published online: doi.org/10.1161/JAHA.118.011318

“Impact of High Volume Energy Drink Consumption on Electrocardiographic and Blood Pressure Parameters: A Randomized Trial.”

Authors: Sachin Shah et al. 

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