The high brain taurine concentration during fetal development of the rat, monkey, rabbit and man at a time when the presumed synthetic pathway, via cysteinesulfinic acid decarboxylase, has little measurable activity suggested a dietary source of taurine to be necessary (3,19,20). In studies investigating the effects on preterm infants of feeding formulas containing different protein quantity and quality and comparing them with infants fed pooled human milk, an interesting pattern of plasma and urine amino acid concentrations was observed. The concentrations of most plasma and urine amino acids were either increased or unchanged when compared with those of infants fed pooled human milk (10,11). Taurine was the striking exception (4). The concentration of taurine in the urine of infants fed casein-predominant formulas was lower from the first week of study than was that of infants fed pooled human milk. The plasma taurine decreased steadily and by the fourth week of study was significantly lower in the plasma of infants fed such formulas than it was in infants fed the pooled human milk. Plasma and urine concentrations of preterm infants fed whey-predominant formulas did not have such consistent decreases, and whether or not there was a decrease was a function of the amount of taurine provided by the formula (4). This effect of commercial formulas on plasma and urine taurine concentrations has been shown to occur in infants on total parenteral nutrition, which is devoid of taurine (14). The small concentrations of taurine in plasma of human preterm infants fed artificial formulas have been documented by others, but not commented on (2).KeywordsBile AcidHuman MilkTotal Parenteral NutritionBile Acid ConjugationTaurine ConcentrationThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.