The Plasma Aminogram. I. Influence of the Level of Protein Intake and a Comparison of Whole Protein and Amino Acid Diets

Abstract

ExtractThe changes in plasma aminogram prcduced by variations in level of protein intake provided either as whole protein or a mixture of amino acids were studied. Controls were 29 normal infants, one to three months of age, fed a standard evaporated milk formula providing 3 to 3.5 g/kg/day of protein (fig. 1 and table II). Results obtained with the lowest protein intake (1.1 g/kg/day) are illustrated in figure 2 and presented in table III. Alterations in the plasma aminogram are noted as early as two days after the reduction in intake and become more pronounced as the feeding is prolonged. The most striking changes are depression of the branched chain amino acids (leucine, isoleucine and valine) and of lysine and tyrosine. Glycine and serine are elevated with glycine showing the greater elevation. Less striking changes are decreased concentrations of threonine, phenylalanine, ornithine, butyrine, cystine and proline.The aminograms obtained with feedings of 1.3 and 1.5 g/kg/day are very similar to those obtained with the more extreme degree of protein reduction ( fig. 3 and table IV). The aminogram after feeding 1.7 g/kg/day remains within the range of average ±1 standard deviation except for the elevation of glycine.A high intake of milk protein, 9 g/kg/day, results in an increase in the levels of a majority of the amino acids ( fig. 5 and table V). The sole exception is glycine, which tends to be low. Marked increases occur in the branched chain amino acids, valine being the most affected; there is also a large increase in the level of proline. The greatest elevations occur in the levels of methionine, which also show the most marked individual variation, elevations ranging from 2 to 35 times normal average value. An apparent tendency of the methionine level to return towards normal with prolonged feeding of the high protein diet is evident on the graph. The significance of this finding must be questioned, however, since the subjects who were maintained the longest on this diet were those who originally did not have the very high levels of methionine.There are some differences in the aminogram when infants are fed the equivalent of 3.5 g/kg/day in the form of amino acids instead of intact protein ( fig. 6 and table VI). On the amino acid diets, lower average plasma values are seen for the branched chain amino acids, alanine, proline, asparagine and citrulline; higher values are observed for threonine and serine. The markedly elevated levels of plasma amino acid observed after feeding 9 g/kg/day of whole protein are not seen after feeding the equivalent amount of nitrogen as an amino acid mixture ( fig. 7 and table VII). There is elevation only of valine and serine. When individual subjects were shifted from the high protein to the high amino acid diet, the pattern shifted within 24 hours. SNYDERMAN, HOLT, NORTON, ROITMAN, PHANSALKAR SpeculationA more precise and sensitive indicator of the state of protein nutrition is needed. While the level of the plasma amino acids changes rapidly with alterations in protein...

Supplementation of Pooled Human Milk with Casein Hydrolysate: Energy and Nitrogen Balance and Weight Gain Composition in Very Low Birth Weight Infants

“…The higher nitrogen intake in the HM-Pr group was associated with higher prefeeding plasma amino acid concentrations. This is not surprising, as there is a well-known correlation between plasma amino acid levels and protein intake (22,23). Plasma amino acid levels taken immediately before a feed have been recommended for screening of any diet-induced, step-by-step accumulation of several amino acids, whereas postprandial amino acid measurements are a useful means of testing the infant's ability to handle amino acid loads in feeds (24).…”

Changes in Serum Albumin, Transferrin and Amino Acid Indices during the First Month of Life in Small-for-Date Infants

“…The homeostasis of free amino acids in the plasma changes characteristically in ex perimental protein undemutrition (low in take of nitrogen) [1,5,34,36], This change is also seen in the clinical syndrome of protein deficiency [6,10,17,39,40] and PEM [6,13,15,17,18,31,32,37], There are only a few studies on homeosta sis of plasma-free amino acids in newborn infants with retarded intrauterine growth. Lindblad [19,20] has reported changes in amino acid levels during the first hours of extrauterine life in children who were under weight and short-for-gestational age as a re sult of hypertension in pregnancy and Mestian et al [26] have shown the postnatal changes in some amino acid ratios in preterm infants (PTI) and SFD infants.…”

Effect of Low, Normal and High Dietary Protein Intake on Urinary Amino Acid Excretion and Plasma Aminogram in Children

“…The influence of protein intake on the plasma aminogram has been studied in adults [35,38] and children [2,31,32] but little is known about the changes in urinary amino acid excretion. In the current study, this has been investi gated in 14 children.…”