Taurine (), or 2-aminoethanesulfonic acid, is a natural product amino sulfonic acid that is widely distributed in animal tissues.[ It is a major constituent of bile and can be found in the large intestine. It is named after Latin (cognate to Ancient Greek , ) meaning bull or ox, as it was first isolated from ox bile in 1827 by German scientists Friedrich Tiedemann and Leopold Gmelin.][ It was identified in human bile in 1846 by Edmund Ronalds.][
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Although taurine is abundant in human organs, it is not an essential human dietary nutrient and is not included among nutrients with a recommended intake level.[
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Taurine is commonly sold as a dietary supplement, but there is no good clinical evidence that taurine supplements provide any benefit to human health.
Discovery and name
Taurine was first isolated from ox bile in 1827 by German scientists Friedrich Tiedemann and Leopold Gmelin.
In nature
Taurine is widely distributed in nature, particularly in animal tissues.
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biosynthesis from the sulfur amino acids (e.g., cysteine);
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active uptake by a possible taurine transporter; and
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the extent of its release from cells by a "volume-sensitive leak pathway".
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Not an essential human dietary nutrient — taurine is excluded among nutrients with a Reference Daily Intake
Taurine is a major constituent of bile, and can be found in the large intestine. Its concentrations in land plants are low or undetectable, but up to a substantial wet weight has been found in algae.
Chemical and biochemical features
Taurine exists as a zwitterion , as verified by X-ray crystallography.
Biosynthesis
Among the diverse pathways by which natural taurine can be biosynthesized, its pathways in the human liver are from cysteine and/or methionine.
Taurine is also produced by the transsulfuration pathway, which converts homocysteine into cystathionine. The cystathionine is then converted to hypotaurine by the sequential action of three enzymes: cystathionine gamma-lyase, cysteine dioxygenase, and cysteine sulfinic acid decarboxylase. Hypotaurine is then oxidized to taurine as described above.
A pathway for taurine biosynthesis from serine and sulfate is reported in microalgae,[ developing chicken ,]
Chemical synthesis
Synthetic taurine is obtained by the ammonolysis of isethionic acid (2-hydroxyethanesulfonic acid), which in turn is obtained from the reaction of ethylene oxide with aqueous sodium bisulfite. A direct approach involves the reaction of aziridine with sulfurous acid.
In 1993, about of taurine were produced for commercial purposes: 50% for pet food and 50% in pharmaceutical applications.
In the laboratory, taurine can be produced by alkylation of ammonia with bromoethanesulfonate salts.
In food
Taurine occurs naturally in fish and meat.[ Typical taurine consumption in the American diet is about per day.][
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Taurine is partially destroyed by heat in processes such as baking and boiling. This is a concern for cat food, as cats have a dietary requirement for taurine and can easily become deficient. Either raw feeding or supplementing taurine can satisfy this requirement.
Both lysine and taurine can mask the metallic flavor of potassium chloride, a salt substitute.
Breast milk
Taurine is present in breast milk, and has been added to many as a measure of prudence since the early 1980s. However, this practice has never been rigorously studied, and as such it has yet to be proven to be necessary, or even beneficial.
Energy drinks and dietary supplements
Taurine is an ingredient in some in amounts of per serving.
Research
Taurine is not regarded as an essential human dietary nutrient and has not been assigned recommended intake levels.[ High-quality clinical studies to determine possible effects of taurine in the body or following dietary supplementation are absent from the literature.][ Preliminary human studies on the possible effects of taurine supplementation have been inadequate due to low subject numbers, inconsistent designs, and variable doses.][
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Safety and toxicity
According to the European Food Safety Authority, taurine is "considered to be a skin and eye irritant and skin sensitiser, and to be hazardous if inhaled;" it may be safe to consume up to 6 grams of taurine per day.
A 2008 review found no documented reports of negative or positive health effects associated with the amount of taurine used in energy drinks, concluding, "The amounts of guarana, taurine, and ginseng found in popular energy drinks are far below the amounts expected to deliver either therapeutic benefits or adverse events".
Animal dietary requirement
Cats
Cats lack the enzyme sulfinoalanine decarboxylase to produce taurine and must therefore acquire it from their diet.
Decreased plasma taurine concentration has been demonstrated to be associated with feline dilated cardiomyopathy. Unlike CRD, the condition is reversible with supplementation.
Taurine is now a requirement of the Association of American Feed Control Officials (AAFCO) and any dry or wet food product labeled approved by the AAFCO should have a minimum of 0.1% taurine in dry food and 0.2% in wet food.
Other mammals
A number of other mammals also have a requirement for taurine. While the majority of dogs can synthesize taurine, case reports have described a singular American cocker spaniel, 19 , and a family of suffering from taurine deficiency treatable with supplementation. on also appear to require dietary taurine. The rhesus monkey, cebus and cynomolgus monkeys each require taurine at least in infancy. The giant anteater also requires taurine.[ (abstracts of animal citations used to provide list of species)]
Birds
Taurine appears to be essential for the development of passerine birds. Many passerines seek out taurine-rich to feed their young, particularly just after hatching. Researchers compared the behaviours and development of birds fed a taurine-supplemented diet to a control diet and found the juveniles fed taurine-rich diets as neonates were much larger risk takers and more adept at spatial learning tasks. Under natural conditions, each blue tit nestling receive of taurine per day from parents.
Taurine can be synthesized by chickens. Supplementation has no effect on chickens raised under adequate lab conditions, but seems to help with growth under stresses such as heat and dense housing.
Fish
Species of fish, mostly carnivorous ones, show reduced growth and survival when the fish-based feed in their food is replaced with soy meal or feather meal. Taurine has been identified as the factor responsible for this phenomenon; supplementation of taurine to plant-based fish feed reverses these effects. Future aquaculture is expected to use more of these more environmentally-friendly protein sources, so supplementation would become more important.
The need of taurine in fish is conditional, differing by species and growth stage. The olive flounder, for example, has lower capacity to synthesize taurine compared to the rainbow trout. Juvenile fish are less efficient at taurine biosyntheis due to reduced cysteine sulfinate decarboxylase levels.
Derivatives
See also
