Gaull G E
Department of Pediatrics, Northwestern University School of Medicine, Chicago.
Pediatrics. 1989 Mar;83(3):433-42.
Taurine was long considered an end product of the metabolism of the sulfur-containing amino acids, methionine and cyst(e)ine. Its only clearly recognized biochemical role had been as a substrate in the conjugation of bile acids. Taurine is found free in millimolar concentrations in animal tissues, particularly those that are excitable, rich in membranes, and generate oxidants. Various lines of evidence suggest one major nutritional role as protecting cell membranes by attenuating toxic substances and/or by acting as an osmoregulator. The totality of evidence suggests that taurine is nonessential in the rodent, it is an essential amino acid in the cat, and it is conditionally essential in man and monkey. Absence from the diet of a conditionally essential nutrient does not produce immediate deficiency disease but, in the long term, can cause problems. Taurine is now added to many infant formulas as a measure of prudence to provide improved nourishment with the same margin of safety for its newly identified physiologic functions as that found in human milk. Such supplementation can be justified by the finding of improved fat absorption in preterm infants and in children with cystic fibrosis, as well as by salutary effects on auditory brainstem-evoked responses in preterm infants. Experimental findings in animal models and in human cell models provide further justification for taurine supplementation of infant formulas.
长期以来，牛磺酸被认为是含硫氨基酸（蛋氨酸和胱氨酸）代谢的终产物。其唯一明确被认可的生化作用是作为胆汁酸结合的底物。在动物组织中，尤其是那些易兴奋、富含细胞膜且会产生氧化剂的组织中，能发现毫摩尔浓度的游离牛磺酸。各种证据表明，牛磺酸的一个主要营养作用是通过减弱有毒物质和/或作为渗透压调节剂来保护细胞膜。所有证据表明，牛磺酸在啮齿动物中是非必需的，在猫中是必需氨基酸，在人和猴子中是条件必需氨基酸。饮食中缺乏条件必需营养素不会立即引发缺乏症，但从长远来看，可能会导致问题。现在，出于谨慎考虑，许多婴儿配方奶粉中添加了牛磺酸，以便在提供更好营养的同时，对于其新发现的生理功能，能保持与母乳相同的安全边际。早产婴儿和囊性纤维化患儿脂肪吸收改善的研究结果，以及对早产婴儿听觉脑干诱发反应的有益影响，都证明了这种添加的合理性。动物模型和人类细胞模型的实验结果为在婴儿配方奶粉中添加牛磺酸提供了进一步的依据。
