The Importance Of Taurine

Unlike the familiar amino acids, taurine -- or L-taurine, to be more particular -- is not used as a building block in proteins. But it is called an "essential" amino acid because the human body, although it desperately needs it, cannot synthetize it; we must get it from our foods. But because taurine is not used for proteins, biochemists classify it as a conditionally essential amino acid.

Adults can produce sulfur-containing taurine from cysteine with the help of pyridoxine, B6. It is possible that if not enough taurine is made in the body, especially if cysteine or B6 is deficient, it might be further required in the diet.

Human milk contains substances called glutamic acid and taurine, which may play a positive role in the body's functioning. Taurine, which is present in large amounts in the developing brain of most species, including the human, may be necessary for optimal nervous system development. Taurine is the second most abundant free amino acid in the milk of human and nonhuman primates.

Taurine has been shown to be essential in certain aspects of mammalian development, and in vitro studies in various species have demonstrated that low levels of taurine are associated with various pathological lesions, including cardiomyopathy, retinal degeneration, and growth retardation, especially if deficiency occurs during development. Metabolic actions of taurine include: bile acid conjugation, detoxification, membrane stabilization, osmoregulation, and modulation of cellular calcium levels. Clinically, taurine has been used with varying degrees of success in the treatment of a wide variety of conditions, including: cardiovascular diseases, hypercholesterolemia, epilepsy and other seizure disorders, macular degeneration, Alzheimer's disease, hepatic disorders, alcoholism, and cystic fibrosis.

Taurine comprises over 50 percent of the total free amino acid pool of the heart. It has a positive inotropic action on cardiac tissue, and has been shown in some studies to lower blood pressure. In part, the cardiac effects of taurine are probably due to its ability to protect the heart from the adverse effects of either excessive or inadequate calcium ion (Ca2+) levels. The consequence of Ca2+ excess is the accumulation of intracellular calcium, ultimately leading to cellular death. Taurine may both directly and indirectly help regulate intracellular Ca2+ ion levels by modulating the activity of the voltage-dependent Ca2+ channels, and by regulation of Na+ channels. Taurine also acts on many other ion channels and transporters. Therefore, its action can be quite non-specific. When an adequate amount of taurine is present, calcium-induced myocardial damage is significantly reduced, perhaps by interaction between taurine and membrane proteins.

Taurine conjugation of bile acids has a significant effect on the solubility of cholesterol, increasing its excretion, and administration of taurine has been shown to reduce serum cholesterol levels in human subjects. In a single-blind, placebo-controlled study, 22 healthy male volunteers, aged 18-29 years, were randomly placed in one of two groups and fed a high fat/high cholesterol diet, designed to raise serum cholesterol levels, for three weeks. The experimental group received 6 grams of taurine daily. At the end of the test period, the control group had significantly higher total cholesterol and LDL-cholesterol levels than the group receiving taurine.

Both plasma and platelet taurine levels have been found to be depressed in insulin-dependent diabetic patients; however, these levels were raised to normal with oral taurine supplementation. In addition, the amount of arachidonic acid needed to induce platelet aggregation was lower in these patients than in healthy subjects. Taurine supplementation reversed this effect as well, reducing platelet aggregation. In vitro experiments demonstrated that taurine reduced platelet aggregation in diabetic patients in a dose-dependent manner, while having no effect on the aggregation of platelets from healthy subjects.

Research in recent years suggests that faulty taurine in metabolism may be associated with certain kinds of epileptic seizures. Insufficient quantities of taurine impedes liver function and, in cats, leads to blindness. Its role in seizures is that taurine acts to stabilize cell walls so the neurons can fire off normally. Seizures result from random firing of nerve cells. Taurine used in quantity to treat epilepsy has only one known side effect, peptic ulcers, which clear up when taurine is discontinued.

Although it is readily apparent that taurine is important in conjugating bile acids to form water-soluble bile salts, only a fraction of available taurine is used for this function. Taurine is also involved in a number of other crucially important processes, including calcium ion flux, membrane stabilization, and detoxification. Some areas of investigation into the clinical uses of taurine have revealed significant applications for this amino acid: congestive heart failure, cystic fibrosis, toxic exposure, and hepatic disorders. Other conditions such as epilepsy and diabetes will require further research before a clear rationale for the use of taurine can be developed.

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