| Abstract: | Thirteen normal female infants were observed from 8 through 111 days of age while receiving a diet providing 1.62 g of protein per 100 kcal, almost entirely from soy-isolate. Clinical observations, growth rates and serum concentrations of albumin were similar to those of female infants fed milk-based formulas providing greater intakes of protein. On the basis of these findings, it is assumed that the requirements for protein and essential amino acids of these infants were no greater than the amounts consumed. Reasons for preferring to express requirements for proteins and amino acids per unit of calorie intake rather than per unit of body weight are presented. The preliminary estimates of requirements presented here are believed applicable when the diet is adequate in total calories and non-nitrogenous essential nutrients, nitrogen is provided primarily in the form of whole proteins, and protein intakes do not greatly exceed the requirement. For reasons discussed, the approach is likely to yield estimates of requirements for some amino acids that are substantially greater than the true requirements. Nevertheless, our estimates of requirements for isoleucine and methionine are distinctly less than those reported by Holt & Snyderman. We conclude that the estimates of Holt & Snyderman from studies of infants fed mixtures of amino acids are less relevant than our estimates to circumstances in which whole proteins are fed in amounts that do not greatly exceed the requirement for protein. |
