Although taurine (2-aminoethanesulfonic acid) was discovered more than 160 years ago, and much of the important research regarding its chemistry and biochemistry has been reported since that time, its real importance with reference to musculoskeletal physiology has only been recognised within the previous decade thanks to a series of fantastic studies by Anna-maria De Luca (Italy). "Human skeletal muscle is such an amazing structure allowing enormous variability in its functions but no doubt its ability to contract is of greatest importance" especially when it comes to human locomotion or our daily shimmy to the weight room for another challenging session. In this issue of MJ we are going on a journey of discovery regarding the use of this complex & multifunction sulfonated amino acid with some revolutionary views on its possible application to muscular performance enhancement.
[ Abundant In Nature ]
Taurine has been shown to be involved in many important physiological processes such as osmoregulation (control of water balance), antioxidant actions (free radical quenching), cell membrane structure, and most importantly for us the control of muscular contractions. The latter will form the basis of this article. To convey a comprehensive explanation of taurine supplementation & how it may effect muscle contractility would involve discussion on calcium transients, chloride conductance and the such, which its outside of the scope of this article and would probably send most of you to sleep within the first paragraph. Therefore I will stick to an applied approach, which will be just as informative (but not as dull).
As the above subheading suggests, taurine is abundant in mammalian skeletal muscle (yes that's you) but its physiological role is not yet completely understood. Let's bring you up to date on what we know so far... "All muscle fibres use Calcium (Ca2+) as their main signalling source for the initiation of contraction". They bind to specific proteins that are constituents of our muscle fibres allowing a controlled and fairly regulated process of muscular movement to occur. For this reason the importance of proteins or amino acids that are involved in the control and expression of Ca2+ will also have a significant effect on the contractile and relaxation properties of muscle fibres (in short they will effect the efficiency of your muscles). One such amino acid that regulates Ca2+ in such a way is taurine1,2. Taurine can work in such a way by modulating the uptake and release of Ca2+ from the muscle cell; it may also control other systems in the intracellular environment including sodium and chloride movement3.
[ Application To Exercise Performance ]
As a conditionally essential amino acid the biological role regarding exercise and taurine is poorly understood, on that score alone is worthy of study, however showing you the data available on muscle injury and exercise may be a more direct route showing its relation to improving or at least maintaining intracellular function. Matsuzaki et al4 is the latest paper to demonstrate a direct effect on muscle taurine concentrations following exercise. Although a rat study, it yields some interesting information regarding the effects of different exercise durations on intramuscular taurine contents. Three groups each carried out either 30, 60, or 100 minute treadmill running after which muscle biopsy analysis showed that there was a significant loss of taurine in the type two fibre (our fast twitch power fibres) but no loss in the type ones (slow twitch endurance fibres). Suggestive of the fact that taurine may be important in even the resistance-trained athlete undertaking endurance type training.
The study did not look directly at isolated single muscle fibres (individual fibre removed from a muscle biopsy sample) rather they looked at fibres from a biopsy taken from different muscle groups of which has previously shown a greater proportion of type one's or two's dependent on which muscle they are looking at (e.g. more type ones in your gastro's than in you pectorals). There have been at least two other studies5,6 that have also shown a loss of taurine into plasma with exercise with the greater loss coming from higher intensity work.
So lets try to fit this information with some applications to what goes on in the real word rather than a clinical setting. Lets take the Body-for-Life programme... we know that we do at least 20 minutes of high intensity aerobic 3 x a week and 3 x resistance work. The result of this intensity of training will no doubt lead to a loss of muscle amino acids including taurine and as Bill Phillips says, "without the spark (exercise) and the fuel (nutrition), there can be no flame (results)". And it is the optimisation of our nutritional programme, which concerns me most regarding intramuscular taurine depletion due to exercise or dietary inadequacies. The use of drinks containing taurine may be one way to combat or even offset taurine loss, which may decrease muscle contractility and consequently performance and training induced physique changes.
[ Nutritional Studies ]
One of the most thorough papers released to date discusses the cytoprotective role taurine feeding can have after exercise induced muscle damage. Let me explain a little; Dawson et al7 studied the effects of 90 minutes of down hill running (known to induce a great deal of muscle damage due to the eccentrics involved) on markers of muscle damage. The study also tried to investigate what impact both elevation and depletion of muscle taurine contents may have on muscle protection/damage. There were three groups involved in the study, one group supplemented with taurine, one with a known inhibitor of taurine uptake, and a placebo group taking water. The results were interesting to say the least... as expected muscle taurine was increased with taurine feeding and depleted with the taurine inhibitor.
The exercise data demonstrated greater markers of muscle damage in the depleted group but an increase in running performance in the taurine group. Although this looks promising no actual measurements of muscle structural change were assessed only indirect biochemical markers of muscle damage.
On a final note there is one study that is not really a feeding study but does demonstrate the effectiveness of taurine on muscle function and force production8. Bakker et al provided data indicating when muscle cells where bathed in taurine versus an innate (a substance with no physiological effect) substitute, a much greater force production in the individual fibres could be measured with the use of taurine. The conclusion to the study suggested that taurine modulated the accumulation of Ca+2 in the sarcoplasmic reticulum (a sac within the muscle where calcium is stored) allowing a greater supply when needed or decreased contents when not during the process of contraction and muscle movement.
This paper gives us some direct evidence of the mechanism as to why if we can change muscles taurine we can improve muscle efficiency, and corroborates to some degree the earlier work we reviewed showing an increased run performance following taurine feeding.
[ Conclusive Proof Just Around The Corner? ]
What of the studies in humans I hear you say? Well it's disappointing for me to say that in all these years of research and scientific advancement no real human data is available regarding muscle performance and the use of taurine supplementation. However there is at least one demonstrating some data to implicate the positive effects of taurine (2g) on cycling time to exhaustion demonstrating an increase compared to placebo9. However the study looked at a combination of supplements including caffeine well known to potentate endurance performance. A further study examining the effects of a 1 gram dose on cognitive function and well being showed that positive benefits occur with relatively low taurine supplementation10.
So what take home message can we use from the data? It's true we do not know what level of supraphysiological supplementation we need to use to effectively enhance performance but we do know for certain is with intense exercise we lose taurine from the muscle in significant quantities. There are a variety of anecdotal report with user's of EAS very own Cytovol, which without knowing the full implications of taurine use, EAS may of come across a great combo supplement that might aid in the replenishment of taurine loss during exercise or inadequate dietary intake. We also know that with ageing there is a loss in muscle taurine11 so the implications for use in an ageing population are probably even more far reaching.
So for now a 2 gram dose has shown some positive effects, which equates to using around 30mg per kg of your bodyweight. Taurine's future in the sports supplement market is unknown but once future research can clear up the unknowns regarding its use in both endurance and resistance exercise, this compound may find a resurgence of popularity to all fitness buffs to whom the discovery that maximizing performance is not possible with optimal nutrition.
Contact Mark James Tallon at mark@oxygenics.co.uk and view his web site at OxygeniX.com.
REFERENCES
1. Huxtable RJ, and Bressler R: Effects of taurine on a muscle intracellular membrane.Biochim Biophys Acta 323: 573-583, 1973
2. Oja SS & Kontro P: Taurine. In: Laijtha A, ed: Handbook of Neurochemistry. New york: Plenum Publ Corp, 501-533, 1983
3. De Luca A, Tricarico D, Pierno S, Conte Camerino D: Ageing and chloride channel regulationin rat fast-twitch muscle fibres. Pflugers Arch 427: 80-85
4. Yasushi M, Miyazaki T, Miyakawa B, Miyakawa S, Bouscarel B, Ikegami T, Tanaka N: Decreased taurine concentration in skeletal muscles after exercise for various durations. Med Sci Sport & Exerc 34 (5): 793 - 797, 2002
5. Ward RJ, Francaux M, Cuisiner C, Sturbois X, De Witte P: Changes in plasma taurine levels after different endurance events. Amino Acids 16 (1): 71-77
6. Cuisinier C, Michotte De Welle J, Verbeeck RK, Portmans JR, Ward R, Sturbois X, Francaux M. Role of taurine in osmoregulation during endurance exercise. Eur J Appl Physiol 87 (6): 489-495
7. Dawson R, Biasetti M, Messina S, Dominy J: The cytoprotective role of taurine in exercise induced muscle injury. Amino Acids 22(4): 309 -324, 2002
8. Bakker AJ & Berg HM: Effect of taurine on SR function and force in skinned fast twitch muscle fibres of the rat. J Physiol 1538:185 -194, 2002
9. Alford C, Cox H, Westcott R: The effects of red bull energy drink on human performance and mood. Amino Acids 21 (2): 139 -50
10. Seidl R, Peyrl A, Nicham R, Hauser E. A taurine and caffeine-containing drink stimulates cognitive performance and well being. Amino Acids 19 (3-4): 635-642
11. Dawson R & Wallace DR: Taurine content in tissues from aged fisher 344 rats. Age 15: 73-81, 1993
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