Taurine, the amino acid in energy drinks like Red Bull, improves the performance of trained middle-distance runners, write sports scientists from the University of Cumbria in England in an article that will soon be published in Amino Acids.
Does taurine improve athletes' performance or not? Yes, say a few Asian studies. [Amino Acids. 2004 Mar; 26(2): 203-7.] [Korean J Nutr. 2003 36:711–719.] No, say Canadian researchers - although taurine supplementation does lead to a slight increase in fat burning. In endurance sports this is often an advantage, but not in the Canadians' study. [Int J Sport Nutr Exerc Metab. 2010 Aug;20(4):322-9.]
The British researchers wanted more clarity on the matter, so performed an experiment with eight young trained middle-distance runners. The subjects did a simulated timed three-kilometre run on the treadmill on two occasions. On one occasion the runners took a placebo two hours before starting the experiment; on the other they took a capsule containing 1000 mg taurine. A period of two hours seems long, but taurine takes longer to enter the bloodstream than other substances.
The figure below shows that with taurine supplementation the subjects completed the distance 12 seconds faster.
Where the increased speed came from is a mystery to the researchers. They found no effects on oxygen uptake [see figure above], heartbeat or fatigue.
And it's not just the British scientists who are in the dark about how taurine works. Human muscle cells don't absorb the amino acid. One theory that has been around for many years is that taurine does something to the membrane of muscle cells which boosts the uptake of substances or the effectiveness of receptors.
Amino Acids. 2012 Aug 2. [Epub ahead of print].