The Antagonistic Effects of Caffeine and Taurine in Energy Drinks

Energy drinks have become a billion-dollar industry, challenging the eye-popping popularity of Starbucks and the likes. Obviously, the main component of energy drinks is caffeine, with some being more potent than others. However, many manufacturers feel the need to add supplemental ingredients to their drinks to “boost” their energizing effects. Whether this is for marketing or real effect is left to be determined.

One of the most popular additives to energy drinks is the non-essential amino acid taurine. Taurine is thought to modulate cell volume, muscle contraction and aid in antioxidant defenses from stress in muscle. Unfortunately for the college student during finals week, the scientific literature does not support using taurine to enhance the vitalizing effects of your caffeinated beverage.

A recent animal study evaluated the muscle ergogenic effects of caffeine alone or in combination with taurine, and found no beneficial effect to adding taurine. Two human, placebo-controlled studies evaluated the effects of using caffeine, taurine or a combination of the two on attention/“energy.” One double-blind, placebo-controlled study compared 80 milligrams of caffeine with or without one gram of taurine and found that co-administration of taurine attenuated the facilitative effects of caffeine. Another study compared 200 milligrams of caffeine with or without two grams of taurine, and further showed that taurine inhibited feelings of vigor normally resulting from caffeine alone.
In summary, the makers of Red Bull and Monster energy drinks may not be out for your best interest when trying to boost your vigor. Not only does taurine have little effect on its own, but it may also have a detrimental effect on the function of your precious caffeine!


One of the more well-characterized muscle-building supplements is the branched-chain amino acid leucine, which has clearly been shown to inhibit muscle protein breakdown while simultaneously increasing the rate of muscle protein synthesis, ultimately promoting substantial muscle growth. Leucine consumption promotes muscle protein accumulation and muscle growth by activating the extremely important nutrient-sensing molecule mTOR, which directly turns off muscle protein degradation while activating muscle protein synthesis. Several studies have shown mTOR activation by leucine intake, specifically during and after resistance exercise.

Although it has been well established that leucine consumption during and after resistance exercise promotes muscle growth, the verdict is still out regarding the performance-enhancing effect from leucine consumption before training. Some of the uncertainty about leucine’s pre-workout consumption stems from the fact that leucine consumption decreases energy production within the muscle cell, potentially diminishing muscle performance during exercise. Another concern about pre-workout leucine consumption involves the likely desensitization of the potent muscle-building hormone insulin, resulting from additional leucine consumed before working out. The final concern involves the negative influence that leucine consumption may have on the central nervous system (CNS) where pre-workout leucine consumption might increase the rate of CNS fatigue, promoting overall sluggishness that decreases exercise performance.

 Pre-workout Leucine Decreases Muscle Cell Energy

In order to build muscle, you’d think that you need to be in an anabolic state at all times— which might also make you believe that the ubiquitous consumption of muscle-building compounds, like leucine, should enhance muscle growth. Yet the reality is being constantly in an anabolic state is not optimal for muscle size and strength. This is mainly because maximal muscle growth requires the perfect blend of muscle-building anabolism combined with energy-producing catabolism. In other words, if you want to build muscle, something has to supply it with energy to function. Well, that’s where catabolic processes like glycogenolysis, the breakdown of glycogen into glucose for energy, play a huge role mainly because intense weightlifting requires glucose for energy. So, although leucine potently stimulates muscle growth, it also prevents the breakdown of glycogen into glucose, reducing available energy that is necessary for muscle contraction. Of course, reduced muscular contraction decreases strength output— which likely compromises the ability to get huge.

 Too Much Leucine Diminishes Muscle Growth

Insulin is the most potent muscle-building hormone produced in the human body, possessing the ability to drastically increase muscle protein synthesis and enhance muscle growth. Insulin achieves this muscle-building effect by binding to the insulin receptor and setting off a cascade of signaling events that eventually activates the enzyme mTOR, triggering muscle growth. However, insulin signaling is very sensitive to overstimulation— where too much insulin signaling can rapidly trigger negative feedback mechanisms that turn down insulin-driven muscle growth.

In addition to the well-known influence that glucose has on insulin secretion and activity, one of the more potent insulin activators is leucine. Interestingly, several studies have shown that insulin resistance can occur with increased amino acid consumption, especially the branched-chain amino acid leucine. The exact mechanism by which leucine modulates insulin sensitivity is currently unclear. Although the decreased insulin sensitivity may be associated with greater insulin secretion induced by leucine, potentially inducing insulin resistance. Of course, insulin resistance from too much leucine consumption would reduce all of insulin’s anabolic properties, meaning a decrease in muscle protein accumulation and therefore muscle growth.

 Leucine Consumption Before Your Workout Promotes Sluggishness and Fatigue

The CNS, composed of the brain and spinal cord, serves as the main “processing center” for the entire nervous system that controls all the workings of your body. Neurons, or nerve cells, are the core components of the CNS that function to receive and confer all of this body-regulating information by electrical and chemical signaling. Neuronal electrical signaling is ultimately converted at the nerve ending or synapse into chemical signaling utilizing neurotransmitters that diffuse across the synapse to adjacent neurons, triggering further electrical signaling down those neurons, which eventually control numerous processes in the body.

Serotonin is a neurotransmitter secreted within the neuronal synapse that induces sleep and drowsiness. Intense exercise has been shown to increase the release of serotonin in the brain, putatively contributing to exercise-induced fatigue. Initially, it was thought that the increase in serotonin alone triggered fatigue. However, it turns out that greater fatigue from exercise is influenced more specifically by an increase in the ratio of serotonin to another neurotransmitter known as dopamine.

The neurotransmitter dopamine has well-defined roles including increased mental arousal, improved motor control and greater levels of motivation, which all tend to improve exercise performance. Therefore, a lower serotonin to dopamine ratio, by either decreasing performance-inhibiting serotonin or increasing performance-enhancing dopamine, should improve exercise capacity. Interestingly, leucine consumption has been shown to inhibit serotonin production by preventing transport of the serotonin-precursor tryptophan into the brain. Because tryptophan is a building block for serotonin, lower tryptophan in the brain reduces serotonin production— suggesting that leucine consumption before exercise could actually mitigate exercise-induced fatigue.

On the other hand, a recent study by Choi et al. showed that leucine also competitively inhibits dopamine production by preventing the uptake of the dopamine-precursor tyrosine into the brain. Since greater brain dopamine function improves physical performance, the finding that leucine reduces dopamine levels in the brain highlights why leucine consumption, especially before exercise when motivation and energy levels are paramount, may have a detrimental influence on physical performance despite leucine’s ability to also reduce serotonin levels.

In conclusion, leucine’s capacity to trigger anabolic processes, such as muscle growth and glycogen production, makes the timing of leucine consumption very important. While leucine consumption during and after lifting weights effectively prevents muscle breakdown while enhancing muscle growth, consuming leucine before your workout appears to have several drawbacks that negatively influence exercise performance— suggesting that pre-workout leucine consumption is not best for optimal muscular performance.

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 biology of exercise as a fellow at Harvard Medical School and Columbia University for over eight years. 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 scientist working at the New York Structural Biology Center doing contract work for the Department of Defense on a project involving national security.

Follow Advanced Molecular Labs On:

Facebook: Advanced Molecular Labs

Twitter: @AML_Nutrition

Instagram: @advancedmolecularlabs


Zheng X, Takatsu S, et al. Acute intraperitoneal injection of caffeine improves endurance exercise performance in association with increasing brain dopamine release during exercise. Pharmacol Biochem Behav 2014;122, 136-143. Einother SJ and Giesbrecht T. Caffeine as an attention enhancer: reviewing existing assumptions. Psychopharmacology (Berl) 2013;225, 251-274. Nehlig A. Is caffeine a cognitive enhancer? J Alzheimers Dis 2010;20 Suppl 1, S85-94. Habowski SM, Sandrock J, et al. The effects of Teacrine, a nature-identical purine alkaloid, on subjective measures of cognitive function, psychometric and hemodynamic indices in healthy humans. Int J Med Sci 2014;11. Ball KT and Poplawsky A. Low-dose oral caffeine induces a specific form of behavioral sensitization in rats. Pharmacol Rep 2011;63, 1560-1563. Kuhman DJ, Joyner KJ and Bloomer RJ. Cognitive Performance and Mood Following Ingestion of a Theacrine-Containing Dietary Supplement, Caffeine, or Placebo by Young Men and Women. Nutrients 2015;7, 9618-9632. Alleman RJ Jr, Canale RE, et al. A blend of chlorophytum borivilianum and velvet bean increases serum growth hormone in exercise-trained men. Nutr Metab Insights 2011;4, 55-63. Tumilty L, Davison G, et al. Oral tyrosine supplementation improves exercise capacity in the heat. Eur J Appl Physiol 2011;111, 2941-2950. Tharakan B, Dhanasekaran M, et al. Anti-Parkinson botanical Mucuna pruriens prevents levodopa induced plasmid and genomic DNA damage. Phytother Res 2007;21, 1124-1126. Hong NY, Cui ZG, et al. p-Synephrine stimulates glucose consumption via AMPK in L6 skeletal muscle cells. Biochem Biophys Res Commun 2012;418, 720-724. Ratamess NA, Bush JA, et al. The effects of supplementation with P-Synephrine alone and in combination with caffeine on resistance exercise performance. J Int Soc Sports Nutr 2015;12, 35. Doherty M and Smith PM. Effects of caffeine ingestion on rating of perceived exertion during and after exercise: a meta-analysis. Scand J Med Sci Sports 2005;15, 69-78. Wang Y, Yang X, et al. Theacrine, a purine alkaloid with anti-inflammatory and analgesic activities. Fitoterapia 2010;81, 627-631. Wilson JM, Joy JM, et al. Effects of oral adenosine-5’-triphosphate supplementation on athletic performance, skeletal muscle hypertrophy and recovery in resistance-trained men. Nutr Metab (Lond) 2013;10, 57. Sprague RS, Bowles EA, et al. Erythrocytes as controllers of perfusion distribution in the microvasculature of skeletal muscle. Acta Physiol (Oxf) 2011;202, 285-292. Trautmann A. Extracellular ATP in the immune system: more than just a ìdanger signal.î Sci Signal 2009;2, pe6. Resende AC, Emiliano AF, et al. Grape skin extract protects against programmed changes in the adult rat offspring caused by maternal high-fat diet during lactation. J Nutr Biochem 2014;24, 2119-2126. Harris RC, Tallon MJ, et al. The absorption of orally supplied beta-alanine and its effect on muscle carnosine synthesis in human vastus lateralis. Amino Acids 2006;30, 279-289. Stellingwerff T, Anwander H, et al. Effect of two beta-alanine dosing protocols on muscle carnosine synthesis and washout. Amino Acids 2010;42, 2461-2472. Baguet A, Koppo K, et al. Beta-alanine supplementation reduces acidosis but not oxygen uptake response during high-intensity cycling exercise. Eur J Appl Physiol 2010;108, 495-503. Hoffman J, Ratamess NA, et al. Beta-alanine and the hormonal response to exercise. Int J Sports Med 2008;29, 952-958. Buford TW, Kreider RB, et al. International Society of Sports Nutrition position stand: creatine supplementation and exercise. J Int Soc Sports Nutr 2007;4, 6. Harris RC, Soderlund K and Hultman E. Elevation of creatine in resting and exercised muscle of normal subjects by creatine supplementation. Clin Sci (Lond) 1992;83, 367-374. Byerrum RU, Sato CS and Ball CD. Utilization of Betaine as a Methyl Group Donor in Tobacco. Plant Physiol 1956;31, 374-377. Brigotti M, Petronini PG, et al. Effects of osmolarity, ions and compatible osmolytes on cell-free protein synthesis. Biochem J 2003;369, 369-374. Hoffman JR, Ratamess NA, et al. Effect of 15 days of betaine ingestion on concentric and eccentric force outputs during isokinetic exercise. J Strength Cond Res 2011;25, 2235-2241. Hawley JA, Gibala MJ and Bermon S. Innovations in athletic preparation: role of substrate availability to modify training adaptation and performance. J Sports Sci 2007; 25 Suppl 1, S115-124. Pasiakos SM, McClung HL, et al. Leucine-enriched essential amino acid supplementation during moderate steady state exercise enhances postexercise muscle protein synthesis. Am J Clin Nutr 2011; 94, 809-818. Saha AK, Xu XJ, et al. Downregulation of AMPK accompanies leucine- and glucose-induced increases in protein synthesis and insulin resistance in rat skeletal muscle. Diabetes 2010; 59, 2426-2434. Blomstrand E, Eliasson J, et al. Branched-chain amino acids activate key enzymes in protein synthesis after physical exercise. J Nutr 2006; 136, 269S-273S. Hillier TA, Fryburg DA, et al. Extreme hyperinsulinemia unmasks insulin's effect to stimulate protein synthesis in the human forearm. Am J Physiol 1998; 274, E1067-1074. Guillet C, Prod'homme M, et al. Impaired anabolic response of muscle protein synthesis is associated with S6K1 dysregulation in elderly humans. Faseb J 2004; 18, 1586-1587. Biolo G, Declan Fleming RY and Wolfe RR. Physiologic hyperinsulinemia stimulates protein synthesis and enhances transport of selected amino acids in human skeletal muscle. J Clin Invest 1995; 95, 811-819. Tremblay F, Lavigne C, et al. Role of dietary proteins and amino acids in the pathogenesis of insulin resistance. Annu Rev Nutr 2007; 27, 293-310. Newgard CB, An J, et al. A branched-chain amino acid-related metabolic signature that differentiates obese and lean humans and contributes to insulin resistance. Cell Metab 2009; 9, 311-326. Yang J, Chi Y, et al. Leucine metabolism in regulation of insulin secretion from pancreatic beta cells. Nutr Rev 2010; 68, 270-279. Filiputti E, Rafacho A, et al. Augmentation of insulin secretion by leucine supplementation in malnourished rats: possible involvement of the phosphatidylinositol 3-phosphate kinase/mammalian target protein of rapamycin pathway. Metabolism 2010; 59, 635-644. Acworth I, Nicholass J, et al. Effect of sustained exercise on concentrations of plasma aromatic and branched-chain amino acids and brain amines. Biochem Biophys Res Commun 1986; 137, 149-153. Newsholme EA and Blomstrand E. The plasma level of some amino acids and physical and mental fatigue. Experientia 1996; 52, 413-415.