Taurine is named after the Latin taurus, which means bull, as it was first isolated from ox bile in 1827 by Austrian scientists Friedrich Tiedemann and Leopold Gmelin. It is often called an amino acid, even in scientific literature, but as it lacks a carboxyl group it is not strictly an amino acid.
Taurine is rumored to be present in both bull semen and urine
While taurine is certainly present in bull livers, many sources claim that taurine is also present in both bull semen and urine. However, one thing is certain, the taurine used in energy drinks such as Red Bull is not taken from these sources.
But the taurine found in energy drinks is synthetic and "vegetarian friendly"
The taurine found in energy drinks is not however a byproduct of bull's testicles, it is a synthetically made substance that is considered to be vegetarian friendly."
The ingredient is taurine, a naturally occurring substance that is present in bull bile and breast milk and has been chemically reproduced for refreshment purposes. No bulls are violated in the process.
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Kirk, Kiaran; and Julie Kirk (1993). "Volume-regulatory taurine release from a human heart cancer cell line". FEBS Letters336 (1): 153–158. doi:10.1016/0014-5793(93)81630-I.
Carey, Francis A.  (2006). Organic Chemistry, 6th ed., New York: McGraw Hill, 1149. ISBN 0-07-282837-4. “Amino acids are carboxylic acids that contain an amine function.”
Lahdesmaki, P (1987). "Biosynthesis of taurine peptides in brain cytoplasmic fraction in vitro.". Int J Neuroscience37 (1-2): 79–84.
Stephen A. Crockett, Cocktail and Bull Story: D.C.’s New Drink Fad, WASHINGTON POST, June 20, 2002, § C, at 1, supra note 41.
Red Bull Mystique Undergoes Scrutiny Over Health, Safety, HOUSTON CHRONICLE, Aug 28, 2001, § Business, at 10
Tim Dowling, Wake-up call: A Student who robbed a supermarket at knifepoint blamed the 11 cans of Red Bull he’d drunk. So what exactly do energy drinks do to you?THE GUARDIAN (London), Nov 9, 2001, § Features, at 6