Plasma Amino Acids in Term Neonates After a Feed of Human Milk or Formula

Abstract

Human milk and formulas with different quantities and qualities of protein were compared by measuring sequential postprandial changes in total amino acids and glycine/valine ratios in plasma of 23 healthy term neonates who had previously been breast-fed ad libitum. At the mean age of 5.5 days the infants received from a bottle 1/36 of their body weight of banked human milk (true protein 0.8 g/100 ml), or formula (1.5 g/100 ml of protein, whey-to-casein ratio 60 : 40 (adapted) or 18 : 82 (non-adapted), or 3.0 g/ml of protein, 60 : 40) after a 3.5-4 hour fast. After the feed, the sum of plasma free amino acids rose and the glycine/valine ratio fell, these changes being significant as soon as 30 min after the start of feeding and maximal at 30 min after human milk but at 60 min after the formulas. Both values returned to prefeeding levels, after human milk in 2-3 hours and after the two 1.5 g/100 ml formulas in about 4 hours, but after the 3 g/100 ml formula were still notably altered at 3.5 hours. The postprandial changes measured seemed to reflect dietary protein intake, and to be unaffected by protein quality (adapted vs. non-adapted formulas). The results show that in studies of plasma amino acids in young infants sampling times should be standardized exactly with respect to type of previous feeding and duration of fasting.

Plasma Amino Acids in Term Neonates and Infants with Phenylketonuria before and after Institution of the Diet

“…We found that alanine rose significantly, which is in good agreement with the results of Tikanoja et al (6). They found that alanine rose 60-120 min after the formula feed, which they explained as being mainly caused by the production of alanine from glucose in peripheral tissues.…”

Biochemistry of Human Milk

“…Human milk amino acids occur in proteins and peptides, as well as a small percentage in the form of free amino acids and glucosamine 3 (Table 4- Tikanoja et al 224 reported that postprandial changes in plasma amino acids in breastfed infants were proportional to dietary intake and were highest for the branched-chain amino acids. Proteins constitute 0.9% of the contents in human milk and range up to 20% in some rabbit species.…”

Composição do leite humano: o alimento ideal

“…Sua composição inclui a alfa-lactalbumina, a lactoferrina, a lisozima, a soroalbumina, as imunoglobulinas e a betalactoglobulina. A alfa-lactalbumina, que constitui cerca de 40% das proteínas do soro do leite humano, é necessária para o transporte de ferro e ainda para a síntese de lactose na glândula mamária 18 .…”