This article is about the chemical compound. For the bovine sub-species, see
Taurine cattle.
Taurine (
), or
2-aminoethanesulfonic acid, is an
organic compound that is widely distributed in animal tissues.
[1]It is a major constituent of
bile and can be found in the
large intestine, and accounts for up to 0.1% of total human body weight. Taurine has many fundamental biological roles, such as conjugation of
bile acids,
antioxidation,
osmoregulation,
membrane stabilization, and modulation of
calcium signaling. It is essential for
cardiovascular function, and development and function of
skeletal muscle, the
retina, and the
central nervous system. Taurine is unusual among biological molecules in being a
sulfonic acid, while the vast majority of biologically occurring acids contain the more weakly acidic
carboxyl group. While taurine is sometimes called an amino acid, and indeed is an
acid containing an
amino group, it is not an
amino acid in the usual biochemical meaning of the term, which refers to compounds containing both an
amino and a
carboxyl group.
[2]
Synthesis and biosynthesis
Synthesis
In 1993, about 5,000–6,000 tons of taurine were produced for commercial purposes: 50% for pet food and 50% in pharmaceutical applications.
[5] As of 2010, China alone has more than 40 manufacturers of taurine. Most of these enterprises employ the
ethanolamine method to produce a total annual production of about 3,000 tons.
[6]
In the laboratory taurine can be produced by alkylation of ammonia with bromoethanesulfonate salts.
[8]
Biosynthesis
Oxidative degradation of cysteine to taurine
Nutritional significance
Taurine occurs naturally in fish and meat.
[10][11][12] The mean daily intake from omnivore diets was determined to be around 58 mg (range from 9 to 372 mg) and to be low or negligible from a strict vegan diet. In another study, taurine intake was estimated to be generally less than 200 mg/day, even in individuals eating a high-meat diet. According to another study, taurine consumption was estimated to vary between 40 and 400 mg/day.
[13]
Energy drinks
Taurine is an ingredient in
energy drinks. Many contain 1000 mg per serving,
[14] and some as much as 2000 mg.
[15]
Magnesium taurate
Physiological functions
Taurine is essential for cardiovascular function, and development and function of skeletal muscle, the retina, and the central nervous system.
[19]
It also acts as an
antioxidant and protects against toxicity of various substances (such as
lead and
cadmium).
[33][34][35][36] Additionally, supplementation with taurine has been shown to prevent oxidative stress induced by exercise.
[37]
Taurine has been shown to reduce the secretion of
apolipoprotein B100 and lipids in
HepG2 cells.
[38] High concentrations of serum lipids and apolipoprotein B100 (essential structural component of
VLDL and
LDL) are major risk factors of
atherosclerosis and
coronary heart disease. Hence, taurine supplementation is possibly beneficial for the prevention of these diseases.
Dietary taurine has a blood cholesterol-lowering effect in young overweight adults. Furthermore, body weight also decreased significantly with taurine supplementation.
[39] These findings are consistent with animal studies.
[40]
Taurine has also been shown to help people with
congestive heart failure by increasing the force and effectiveness of heart-muscle contractions.
[41]
Taurine levels were found to be significantly lower in
vegans than in a control group on a standard American diet. Plasma taurine was 78% of control values, and urinary taurine was 29%.
[42]
In cells, taurine keeps potassium and magnesium inside the cell, while keeping excessive sodium out. In this sense, it works like a diuretic. Because it aids the movement of potassium, sodium, and calcium in and out of the cell, taurine has been used as a
dietary supplement for epileptics, as well as for people who have uncontrollable facial twitches.
[43]
According to animal studies, taurine produces an
anxiolytic effect and may act as a modulator or antianxiety agent in the central nervous system by activating the
glycine receptor.
[44][45][46]
A study of mice hereditarily unable to transport taurine suggests it is needed for proper maintenance and functioning of
skeletal muscles.
[47] In addition, it has been shown to be effective in removing fatty liver deposits in rats, preventing liver disease, and reducing
cirrhosis in tested animals.
[48][49] Evidence indicates taurine may be beneficial for blood pressure in male rats. A single intravenous taurine supplementation resulted in measurable decreases in blood pressure. However, when rats were supplemented with taurine in their drinking water, only female rats showed an increase in blood pressure. Both genders showed significant
tachycardia.
[50]
Taurine is necessary for normal skeletal muscle functioning.
[47] Mice with a genetic taurine deficiency had a nearly complete depletion of skeletal and cardiac muscle taurine levels and a reduction of more than 80% of exercise capacity compared to control mice. Taurine can influence (and possibly reverse) defects in nerve blood flow, motor nerve conduction velocity, and nerve sensory thresholds in experimental diabetic neuropathic rats.
[51][52]
In diabetic rats, taurine significantly decreased weight and decreased
blood sugar.
[53] Likewise, taurine administration to diabetic
rabbits resulted in 30% decrease in serum glucose levels.
[54] According to the single study on human subjects, daily administration of 1.5 g of taurine had no significant effect on insulin secretion or insulin sensitivity.
[55] There is evidence that taurine may exert a beneficial effect in preventing diabetes-associated
microangiopathy and tubulointerstitial injury in
diabetic nephropathy.
[56][57]
Safety and toxicity
Taurine is involved in a number of crucial physiological processes. However, its role in these processes is not clearly understood and the influence of high taurine doses on these processes is uncertain. A substantial increase in the plasma concentration of growth hormone was reported in some epileptic patients during taurine tolerance testing (oral dose of 50 mg per kg body mass per day), suggesting a potential to stimulate the hypothalamus and to modify neuroendocrine function.
[62] A 1966 study found an indication that taurine (2 g/day) has some function in the maintenance and possibly in the induction of
psoriasis.
[13] Three later studies failed to support that finding.
[63][64][65] It may also be necessary to take into consideration that absorption of taurine from beverages may be more rapid than from foods.
[13]
Taurine has an observed safe level of supplemental intake in normal healthy adults at up to 3 g/day.
[66] Even so, a study by the European Food Safety Authority found no adverse effects for up to 1,000 mg of taurine per kilogram of body weight per day.
[67]
A review published in 2008 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".
[68]
In animal nutrition
Taurine is an essential dietary requirement for feline health, since house
cats (and all members of the
cat family) cannot synthesize the compound. The absence of taurine causes a cat's
retina to slowly degenerate, causing eye problems and (eventually) irreversible blindness – a condition known as
central retinal degeneration (CRD),
[69][70] as well as hair loss and tooth decay. Decreased plasma taurine concentration has been demonstrated to be associated with
feline dilated cardiomyopathy.
[71] 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.
[72]
Research suggests taurine is essential to the normal development of
passerine birds. Many passerines seek out taurine-rich
spiders to feed their young, particularly just after hatching. Researchers compared the behaviors 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.
[73]
Prematurely born infants deficiency risk
Prematurely born infants are believed to lack the enzymes needed to convert
cystathionine to
cysteine, and may, therefore, become deficient in taurine. Taurine is present in
breast milk, and has been added to many infant formulas, 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.
[74]
Other uses
In cosmetics and contact lens solutions
Since the 2000s cosmetic compositions containing taurine have been introduced, possibly due to its
antifibrotic properties. It has been shown to prevent the damaging effects of
TGFB1 to hair follicles.
[75] It also helps to maintain skin hydration.
[76]
Taurine is also used in some contact lens solutions.
[77]
See also
