By Michael J. Rudolph, Ph.D.

The consumption of different energy drinks is widespread due to their supposed ability to boost energy and improve exercise performance. Indeed, energy drinks are one of the most popular supplements among athletes with approximately 73 percent of all collegiate athletes in the United States consuming them.¹ The performance-enhancing effect from energy drinks is attributed to several ingredients found in these drinks including the all-important compounds caffeine and taurine.

Caffeine and Taurine Independently Strengthen Muscle Contraction

Caffeine is a regularly used performance-enhancing aid typically taken to stimulate the central nervous system, improving alertness and focus for a better workout. Caffeine can also improve exercise performance by directly increasing the cellular concentration of the molecule cyclic AMP (cAMP). An increase in cAMP activates several cellular signaling cascades that trigger the breakdown of fat (lypolysis) and glycogen (glycolysis) providing energy to the muscle while training. Greater cAMP levels also enhance muscular contraction force by increasing calcium levels within the muscle cell. Calcium permits the interaction between the muscle proteins actin and myosin required for muscular contraction. Thus, more calcium causes more actin and myosin interactions, which generates a stronger muscular contraction. Taurine is a non-proteinaceous amino acid that augments a wide array of metabolic and physiological processes including osmoregulation, mitochondrial function and energy metabolism, making this compound a potentially formidable ergogenic aid. Taurine also regulates intracellular calcium within muscle like caffeine, giving this compound the capacity to augment muscle contractile force as well.  

Combined Caffeine and Taurine Use Does Not Enhance Exercise Performance

Because caffeine and taurine augment muscular contraction in a similar fashion, several studies looked at the ability of these two compounds, showing caffeine and taurine intake improved reaction time, alertness, upper body muscular power and aerobic and anaerobic performance, while a few other investigations failed to demonstrate improvements in sprinting ability², time to exhaustion³ or enhance peak power.⁴ Regrettably, many of these studies did not use isolated doses of caffeine and taurine; instead simply using popular energy drinks, which effectively discounted the possible contribution of the other ingredients found in these drinks toward the performance enhancement displayed in each study. To address this major shortcoming in these previous investigations, a more recent study by Ozan et al.⁵ probed the effect of caffeine and taurine co-ingestion only at doses found in commercially available energy drinks on power output while doing sprints on a bike. Despite the belief caffeine and taurine enhance exercise performance relative to placebo, the combined intake of caffeine and taurine at doses equivalent to commercial energy drinks did not improve power output during repeat-sprint cycling performances in this study. The simultaneous intake of caffeine and taurine also seemed to trigger greater levels of muscle fatigue especially at later points within the training protocol. This undesirable performance effect occurred along with increased heart rates and glycolytic metabolic byproducts (e.g., lactic acid), further indicating caffeine and taurine are not a performance-enhancing combination and may very well diminish physical performance, causing premature fatigue.

Taurine and Caffeine Intake May Trigger Irregular Heartbeat

In addition to the apparent inability of caffeine and taurine to improve physical performance, overconsumption of energy drinks containing caffeine and taurine may also lead to very dangerous health outcomes such as an irregular heartbeat (cardiac arrhythmia) along with other less severe side effects such as gastrointestinal upset or insomnia⁶, making the use of these popular energy drinks ill-advised. Several reports link cases of sudden cardiac death to excessive energy drink use even in otherwise healthy individuals.⁷ Although energy drinks may be bad for your health, consuming normal amounts of caffeine does not appear to alter heart function⁸ or increase susceptibility to irregular heartbeat.⁹ Furthermore, normal taurine use directly, or indirectly, regulates certain ion channels in the heart where it has been shown taurine can actually mitigate the risk for an irregular heartbeat.¹⁰ In fact, taurine is often regarded as an antiarrhythmic agent lessening the chance for an irregular heartbeat. However, the amount of taurine found in energy drinks far exceeds the standard amount of taurine typically consumed – promoting the concern for possible adverse cardiac effects mediated by excessive taurine ingestion, especially when combined with caffeine found in the typical energy drink.

Though the exact mechanism triggered by energy drinks that may induce an irregular heartbeat is not well described, a study by Ellerman et al.¹¹ investigated the electrophysiologic effects of caffeine and taurine on the heart. In this study, rabbit hearts were directly exposed to caffeine or taurine and then their function was measured by electrocardiography also known as an EKG. After caffeine treatment, researchers observed a much greater trend toward an irregular heartbeat in the lower chambers of the heart (ventricles) in a dose‐dependent manner – a phenomenon known as a ventricular arrhythmia. A similar exposure of these hearts to taurine in this study also resulted in significantly more ventricular arrhythmias (abnormal heartbeat within the lower heart chambers). Interestingly, there were considerably less ventricular arrhythmias with low‐dose taurine exposure caused, suggesting the higher amounts of taurine precludes the normally antiarrhythmic influence of lower amounts of taurine. Since most popular energy drinks contain a lot of taurine at 1 gram per 250 milliliter can, the antiarrhythmic influence of taurine is likely nonexistent in the standard energy drink. Taken together, these findings uncover the potentially dangerous outcomes promoted by the consumption of energy drinks, strongly indicating against their use at this time.

 Glossary of Terms

1. Ergogenic - intended to enhance physical performance.
2. Ventricular arrhythmia - abnormal heartbeats that originate in the lower heart chamber called the ventricles.

For most of Michael Rudolph’s career he has been engrossed in the exercise world as either an athlete (he played college football at Hofstra University), personal trainer or as a research scientist (he earned a B.Sc. in Exercise Science at Hofstra University and a Ph.D. in Biochemistry and Molecular Biology from Stony Brook University). After earning his Ph.D., Michael investigated the molecular biological effects of exercise as a fellow at Harvard Medical School and Columbia University. That research contributed seminally to understanding the function of the incredibly important cellular energy sensor AMPK – leading to numerous publications in peer-reviewed journals including the journal Nature. Michael is currently a Senior Scientist working at the New York Structural Biology Center where he investigates the molecular nature of human illness and disease.

© Published by Advanced Research Media, Inc., 2023

© Reprinted with permission from Advanced Research Media, Inc.

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