Fasting plasma free amino acids of infants and children consuming cow milk proteins.

We have analyzed the fasting plasma aminograms of 165 infants and small children. Mean age was 17 months (range, 3-42 months). The majority had been consuming a diet in which all protein was supplied by calcium caseinate, the remainder a modified cow milk formula. Protein provided less than 6.4% of energy for 8 children, 6.4%-7% of energy for 81 children, 8% of energy for 42 children and greater than 8% of energy for 34. Only the values for the concentrations of total essential amino acids, valine, and taurine at less than 6.4% of energy as protein were significantly lower than corresponding values at higher intakes of protein. Analysis of the remainder of the data revealed no significant differences in either absolute concentrations or molar fractions among differing levels or sources of protein intake. Interindividual variation in concentrations of amino acids was greater than that resulting from changes in the level of intake of high quality protein when 6.4% or more of energy was provided as protein.