Taurine Introduction

The end product of L-cysteine metabolism, taurine is classified as a nonprotein, conditionally essential amino acid. With the assistance of pyridoxine, humans may produce sulfur-containing taurine from the amino acid cysteine. Its dietary essentiality, nevertheless, is witnessed in newborn diets, as it is critical for normal retinal and brain development; and in adults whom are either cysteine or vitamin B6 deficient.

Taurine is not a prime component of muscular proteins. It exists as the principal free intracellular amino acid which stabilizes cell membranes in electrically active tissues such as the brain and heart. The highest concentrations of taurine in the human body are found in the central nervous system, heart tissues (myocardium), retina, platelets, neutrophils, and skeletal and smooth muscles. Taurine is important in numerous metabolic processes. Processes with reference to certain visual pathways, heart, brain and nervous system functioning, and the conjugation of bile acids, all require sufficient amounts of bodily taurine.

Taurine remains unique among all biological amino acids. First, taurine is a sulfonic acid rather than a carboxylic acid. Secondly, it is a beta-amino rather than an alpha-amino acid. And lastly, unlike many other protein amino acids which contain large number of chiral centers, taurine does not have one. This uniqueness provides the body with certain antioxidant and detoxifying properties, fat absorption and solubilization, and a medium in which the facilitation of sodium, potassium, calcium, and magnesium may take place. [1]

Taurine is abundant in nearly all mammalian protein. Higher sources of this amino acid include egg, fish, meat, and milk products. [2] Vegetable proteins contain trace amounts of taurine. This may be of considerable relevance to vegetarians, as these persons may ingest insufficient amounts of the amino acid derivative. Because of taurine’s abundance in the average adult diet, a specific food graph has been omitted from this section. Of note, there are no known nutrient interactions with dietary or supplementary taurine.

Among taurine’s most important benefits is its ability to be used as a therapeutic agent for the heart. Taurine is often deemed as a safe and effective tool for the management of various forms of cardiovascular disease and arrhythmias. [3] Persons suffering from this condition may find benefit in supplementary taurine in dosages ranging from 3 to 6 grams per day, for no less than a three week period. Taurine assists the heart in regulating blood pressure and platelet aggregation, while reducing serum cholesterol levels. [4-6] Positive levels of taurine in human subjects have also proved beneficial at regulating intracellular calcium levels of the heart. Calcium is critical in preventing myocardial damage; a direct result of the cell death attributed to imbalances of this integral mineral. [7]

In vitro studies support the theory that taurine is important in our overall growth and development. [8] Humans’ ability to synthesize dietary taurine is quite limited. This fact is highlighted in commercially available infant formulas. Like adults, infants do not readily synthesize or store taurine. Clinical application has shown taurine deficiency to be responsible for neurological defects, growth retardation, and retinal degeneration. [9] Therefore, taurine may act as a potent growth modulator in humans.

Individuals with Type I, or insulin-dependant diabetes may find an increased benefit with supplemental taurine. Taurine has been shown to lessen the problematic symptoms of this disease. Supplementation with this amino acid has been of assistance in influencing proper blood glucose and insulin levels. Taurine has also been proven to increase glycogen synthesis and assist in the overall integrity and functioning of the beta cells located in the pancreas. [10] As well, taurine is instrumental in correcting abnormal plasma and platelet taurine in these persons. [11]

Cystic Fibrosis patients often exhibit a malabsorption of critical nutrients in the ileum, including taurine. Clinical studies have shown 30 mg/kg of taurine taken daily over a four month period proved significant in replenishing blood levels of taurine and aiding in the decrease in fecal fatty acids. [12] The severity in the impairment of bile acid conjugation and steatorrhea, which many times accompany cystic fibrosis, may also be significantly lessened by supplemental taurine.

Because of the abundance of taurine located in the vertebrate retina, proper intake of taurine may be especially useful in protecting the photoreceptors from damage in this area of the eye. [13] Retinal taurine is also needed to regulate osmotic pressure, stabilize cell membranes, and to act as an antioxidant by scavenging free radicals. Retinitis pigmentosa may also be directly associated to inadequate amounts of bodily taurine, as well as an abnormality in taurine metabolism.

Areas of ongoing research into taurine supplementation include; alcohol dependence and withdrawal, seizure and hepatic disorders, and Alzheimer's disease. [14, 15]

There has been no established Recommended Daily Allowance (RDA) for taurine. Administration of supplemental taurine is usually oral, and average dosages range from 500 milligrams to 3 grams daily in divided dosages. Although there is no established RDA, the U.S. National Academy of Sciences recommends that healthy people achieve .36 grams of highly bioavailable protein for each pound of bodyweight -equaling 0.8 grams of protein, per kilogram of bodyweight. Taurine (along with methionine, cystine, and cysteine) is a sulfur-containing amino acid (S-) and its requirements for various age groups is listed below:

[12]

Taurine Deficiencies

Deficiencies of taurine are often times the result of underlying metabolic disorders. Complications due to prolonged and severe deficiencies include; cardiac arrhythmias, platelet formation disorder, physical and emotional stress, intestinal problems, and overgrowth of candida (yeast-like fungus located in the mouth, intestines, and vagina). Deficiencies manifest themselves through the excessive loss of taurine via urine. Zinc deficiency may also be a direct indicator, as it is in direct correlation to taurine deficiency. Those at greatest risk for developing a deficiency include diabetics and individuals with substance abuse problems; especially alcoholics.

Taurine Toxicities

Taurine, even at higher dosages, has proven safe in various human and animal studies. A dosage of 2 grams daily administered to psoriasis patients has resulted in temporary, intense itching. [17] Also, epileptic patients supplementing with 1.5 grams of taurine daily reported nausea, headache, dizziness, and gait disturbances. [18] More research is needed to assess this probability of toxicity in persons not suffering from these specific conditions.

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4. Schaffer S, Takahashi K, Azuma J. Role of osmoregulation in the actions of taurine. Amino Acids. 2000;19(3-4):527-46.

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6. Mizushima S, Nara Y, Sawamura M, Yamori Y. Effects of oral taurine supplementation on lipids and sympathetic nerve tone. Adv Exp Med Biol 1996;403:615-622.

7. Van Gelder NM. Neuronal discharge hypersynchrony and the intracranial water balance in relation to glutamic acid and taurine redistribution: migraine and epilepsy. In: Pasantes-Morales H, Martin DL, Shain W et al., eds. Taurine: Functional Neurochemistry, Physiology, and Cardiology. New York City, NY: Wiley-Liss; 1990:Vol. 351.

8. Gaull GE, Wright GE, Tallen JJ. Taurine in human lymphoblastoid cells: uptake and role in proliferation. In: Kuriyama J, Huxtable RJ eds. Sulfur Amino Acids: Biochemical and Clinical Aspects. New York City, NY: Alan R. Liss; 1983:297-303.

9. Bradford RW, Allen HW. Taurine in health and disease. J Adv Med 1996;9:179-199.

10. Timbrell JA, Seabra V, Waterfield CJ. The in vivo and in vitro protective properties of taurine. Gen Pharmac. 1995;26:453-462.

11. Franconi F, Bennardini F, Mattana A, et al. Plasma and platelet taurine are reduced in subjects with insulindependent diabetes mellitus: effects of taurine supplementation. Am J Clin Nutr 1995;61:1115-1119.

12. Smith U, Lacaille F, Pepage G, et al. Taurine decreases fecal fatty acid and sterol excretion in cystic fibrosis. A randomized double-blind study. Am J Dis Child 1991;145:1401-1404.

13. Gonzalez-Quevedo A, Obregon F, Santiesteban Freixas R, et al. Amino acids as biochemical markers in epidemic and endemic optic neuropathies. Rev Cubana Med Trop. 1998;50 Suppl:241-4.

14. Ikeda H. Effects of taurine on alcohol withdrawal. Lancet 1977;2:509.

15. Matsuyama Y, Morita T, Higuchi M, Tsujii T. The effect of taurine administration on patients with acute hepatitis. ProgClin Biol Res 1983;125:461-468.

16. Zest for life information page. “RDA of amino acids.” (1999-2003) http://www.anyvitamins.com/amino-acids/rda-amino-acids.htm (14 Sept. 2004).

17. Kendler BS. Taurine: An overview of its role in preventative medicine. Prev Med 1989;18:79-100.

18. Van Gelder NM, Sherwin AL, Sacks C, Andermann F. Biochemical observations following administration of taurine to patients with epilepsy. Brain Res 1975;94:297-306.