The lead researcher behind a high-profile paper showing energy drinks increase heart contraction rates has rejected claims by Monster Beverage Corp that the paper is ‘alarmist’ and stressed that “whether this increase in contractility is generally beneficial or not cannot be deducted from our study”.
Daniel K. Thomas, M.D.is principal investigator of an unpublished study from the University of Bonn showing that healthy adults who consumed energy drinks containing caffeine and taurine had higher heart contraction rates one hour later.
The research was presented by Dr Jonas Dörner, M.D. from the university's cardiovascular imaging section at the annual meeting of the Radiological Society of North America, which issued an accompanying press release that prompted a slew of headlines warning of the health risks of energy drinks.
Whether this increase in contractility is generally beneficial or not cannot be deducted from our study
But the paper - which is currently being prepared for submission to a peer-reviewed journal - does not in fact state that a short-term increase in heart contraction rate is in itself a health concern, merely that it warrants further investigation, Dr Thomas told FoodNavigator-USA.
“Although, energy drinks have previously been shown to enhance athlete’s endurance, this is the first study using advanced imaging technology (MRI strain imaging) to directly demonstrate the impact of an energy drink on myocardial contraction.
“Whether this increase in contractility is generally beneficial or not cannot be deducted from our study or from the current literature, but warrants further investigation. Specifically, the dose dependency of this effect and long-term effects have yet to be investigated.”
We did not state that a short-term increase in heart contraction is a health concern
He stressed: “We did not state that a short-term increase in heart contraction is a health concern… [And] we did not state that energy drinks or taurine per se trigger arrhythmia.
“We do not state that the findings of our study link energy drinks to arrhythmia. However, it is known that drugs that have an impact on myocardial contractility may have a (dose-dependent) pro-arrhythmogenic effect.”
Contrary to a statement issued by Monster this week, he added: “We did not state that based on the findings of our study the consumption of energy drinks should be restricted.”
He also noted that “Monster Beverage Corporation itself does not recommend children, pregnant women or those sensitive to caffeine to consume its products. In this regard we agree with the manufacturer.”
No significant differences in heart rate or blood pressure
The study revealed that volunteers who consumed an energy drink* had significantly increased peak strain and peak systolic strain rates (measurements for contractility) in the left ventricle of the heart an hour later, according to cardiac MRI data.
It found no significant differences in heart rate, blood pressure or the amount of blood ejected from the left ventricle of the heart between the volunteers' baseline and second MRI exams.
While Dr Thomas did not say that the increase in heart contraction rates was itself a cause for alarm, the press release from the Radiological Society cited Dr Dörner’s “concerns” about energy drinks’ “potential adverse side effects on heart function, especially in adolescents and young adults”.
In the release, Dr Dörner also asserted that there is “little or no regulation of energy drink sales”, and advised children and people with known cardiac arrhythmias to avoid energy drinks “because changes in contractility could trigger arrhythmias”.
Finally, he claimed that energy drinks contained up to three times the amount of caffeine as coffee or cola, a claim that has been challenged repeatedly by the beverage industry as factually inaccurate.
Monster: Taurine helps the heart function more efficiently
Monster immediately issued a statement asserting that: “No evidence exists that increased contractility causes arrhythmia.
“Although he [Dr Dörner] concludes that the consumption of energy drinks should be restricted based on his study, this conclusion is unsupported by his data and highly misleading.”
In fact, claimed Monster, the research “confirms what scientists have known for decades: Taurine helps the heart function more efficiently by improving the pumping force of the heart without any changes in blood pressure or heart rate.
“Peer reviewed studies demonstrate that taurine has been used effectively to treat patients with congestive heart failure and to improve athletic performance.”
* The drink contained taurine (400 mg/100 ml) and caffeine (32 mg/100 ml), although Dr Dörner did not say how many mls in total were consumed.