The study - conducted by researchers at the University of Bonn in Germany and presented at the annual meeting of the Radiological Society of North America - 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.
The research - presented by Dr Jonas Dörner, M.D. from the university's cardiovascular imaging section - 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.
It is not clear how long-lasting the effects were as the researchers only collected data at baseline and one hour post consumption.
Dr Dörner: Energy drinks have 'potential adverse side effects on heart function, especially in adolescents'
While Dr Dörner did not say that the increase in heart contraction rates was itself a cause for alarm, a press release accompanying his presentation issued by the Radiological Society cited his “concerns” about energy drinks’ “potential adverse side effects on heart function, especially in adolescents and young adults”.
In the press release, which has generated a slew of headlines warning about health risks from energy drinks, he 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 - a stimulant that can influence the central and the peripheral nervous system - as coffee or cola, a claim that has been challenged repeatedly by the beverage industry as factually inaccurate.
Monster Beverage Corp: Taurine helps the heart function more efficiently by improving the pumping force of the heart without any changes in blood pressure or heart rate
In a statement describing his presentation as “alarmist and misleading”, Monster said: “No evidence exists that increased contractility causes arrhythmia.
“The author's study does not document a negative effect on heart function. Although he 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, Dr Dörner’s 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.”
According to “Monster Beverage independent medical consultants” Dr Michael H. Forman of the Tri-City Emergency Medical Group in San Diego County (an emergency room specialist who has treated thousands of cases of cardiac arrhythmia), and physician Bob Arnot, M.D., “This effect of taurine, called contractility, is widely considered to be beneficial.”
The study does not document a negative effect on heart function
Meanwhile, Dr Dörner’s claim that energy drinks typically contain more caffeine than coffee is also “false and inaccurate”, it added: “Ounce per ounce, leading energy drinks contain about half the caffeine of coffeehouse coffee, such as Starbucks.”
The American Beverage Association - which noted that the study included “only 18 adults” - added: “Caffeine is a safe ingredient and is consumed every day in a wide variety of foods and beverages, including energy drinks.”
Study: Energy drinks and shots contribute “minimally” to total caffeine intakes
While the FDA has raised concerns about the recent proliferation of caffeine-containing products on the market, particularly those marketed at young people, recent data suggests energy drinks and shots contribute “minimally” to total caffeine intakes (click here).
Addressing safety concerns about caffeine in an IFT webinar last month, toxicologist, Dr James Coughlin said that “clinical studies show that single doses of caffeine under 400mg do not increase the frequency of cardiac arrhythmias in healthy persons or patients with ischemic heart disease or those with serious ventricular ectopia.”
Caffeine is listed as GRAS (generally recognized as safe) for use in cola-type beverages at 200ppm or 71 mg per 12oz. If it is used in energy drinks or other foods and beverages, a company must prove it is GRAS for its intended use and in the amount used.
* 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.
Click here to read the response by principal investigator Daniel K. Thomas, M.D.