One of the biggest questions surrounding energy drinks is whether they are more dangerous for the heart than caffeine from coffee. Some people worry it’s the combination of ingredients, not just the caffeine content itself, which makes energy drinks more dangerous. As a biochemist studying energy drinks, I strive to better understand this risk by reviewing the latest research on caffeine and energy drink ingredients. In this Research Recap, we’ll review an experiment on how caffeine and taurine affect the contraction behavior of the heart muscle.
The Research Article
This research article was published in the journal BMC Cardiovascular Disorders and the full article is available here.
Why is this experiment important?
*If you’re a scientist, please forgive my use of the term “experiment” and “scientists”. I use these terms for convenience to refer to the research study and to the research group/study authors, respectively
The goal of this experiment was to find out how caffeine, taurine, and a combo of the two affects the contraction force and contraction duration of the myocardium. The myocardium is the middle layer and is the muscular substance of the heart. The myocardium is also referred to as the cardiac muscle (heart muscle) [thank you, Online Biology Dictionary].
Other studies have looked at the effect of energy drinks on heart rate, blood pressure, and cardiac output. The results have been mixed and inconsistent: one study found energy drinks elevated blood pressure, heart rate, and cardiac output; another study found no change in heart rate; another study found no change in cardiac output.
In this experiment, the scientists treated isolated heart tissue samples with liquid solutions of caffeine, taurine, or a caffeine-taurine combination. By isolating the heart tissue and these two energy drink ingredients, the scientists removed the effect of any other reactions in the body and interactions between any other ingredients in the energy drink. By looking specifically at the heart muscle tissue itself and by using isolated solutions of caffeine and taurine, the scientists offer a giant magnifying glass on what caffeine and taurine are doing to the human heart muscle (myocardium).
What did they find?
In this experiment, the scientists found that caffeine significantly increased the contraction force (Isometric contractile force, ICF) and caused marginally small but statistically significant decreases in the contraction duration.
Taurine had no effect. Not only did it fail to change the contraction force or contraction duration, it also failed to alter any of the effects of caffeine. In other words, it didn’t matter if caffeine was by itself or with taurine, the results for the combo were the same as the results from caffeine by itself.
This experiment suggests if energy drinks increase the strength of muscular contractions (called a “positive inotropic effect”), it’s not because of the taurine. In this experiment, caffeine is the only one causing the positive inotropic effect, and taurine does nothing to increase or mitigate caffeine’s effect.
Where is the “Moment of Modesty”?
There is a moment of modesty in every good research paper. As scientists, we are trained to accept that there are things we can never know for 100% certainty. In every good research paper, the authors admit where their experiment has limitations and advise caution for interpreting their results.
The moment of modesty in this research paper is when the scientists admit it’s not definite that a significant difference in heart muscle contraction force as measured in an isolated heart tissue sample will be significant in the human body. The goal of this experiment was not to confirm what is happening in the body but to provide insight into the relationship between caffeine and taurine with respect to the heart muscle.
“Due to the nature of our in-vitro model, our results are intended to complement rather than contradict the results of the in-vivo work we used as a background for our discussion.” – authors of this research article
In this experiment, the scientists found that taurine has no interaction with caffeine when it comes to the contractile force and duration of the myocardium. Regardless whether caffeine is by itself or combined with taurine, caffeine increases the contractile force and decreases contraction duration. The scale of these changes is not representative of what happens in the human body, but it provides a magnifying glass on how taurine and caffeine work together (or ignore each other, really).
For the Complete Guide to Energy Drink Ingredient Interactions, visit this page.
For more research recaps, they’re compiled here.
I’ve researched the science and safety behind energy drinks and their ingredients since 2003. This book is the culmination of my research:
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