RESUMO
We report measurements of urinary inorganic sulfate (iSO4) in 38 very low birth weight (VLBW) premature infants receiving various protein intakes in the first 2 months of life. The primary source of urinary iSO4 is the metabolism of amino acids containing sulfur (methionine, cysteine, taurine). It was hypothesized that urinary iSO4 excretion would be increased in VLBW infants fed the relatively high concentrations of protein in mother's own milk (HM), mother's own milk fortified with 0.85 gm/dl bovine whey (fortified HM), and a special formula for premature infants (Similac Special Care, 20 cal/oz), and that urinary iSO4 excretion would correlate with calcium excretion. VLBW premature infants fed HM (protein intake 3.3 gm/kg day) excreted very small amounts of urinary iSO4 compared with infants fed fortified HM (4.5 gm/kg/day protein), Similac SC (2.9 gm/kg/day protein), or Similac (2.7 gm/kg/day protein), all three of which contain bovine whey. Unlike the case in adults, there was no correlation between either total protein intake and urinary calcium excretion or urinary iSO4 excretion. There was, however, a significant correlation between methionine intake and urinary iSO4 excretion (r = 0.48). We speculate that increased urinary iSO4 excretion is indicative of an overload of sulfur-containing amino acids, namely methionine, present in bovine whey protein. The data also support the ability of premature infants to catabolize relatively large quantities of sulfur-containing amino acids after 2 weeks of age.
Assuntos
Recém-Nascido de Baixo Peso/urina , Proteínas do Leite/metabolismo , Sulfatos/urina , Animais , Cálcio/urina , Bovinos , Feminino , Humanos , Alimentos Infantis , Recém-Nascido , Metionina/metabolismo , Leite Humano/metabolismoRESUMO
The changes in fat concentration and cumulative fat losses that occur during the delivery of human milk using two different continuous infusion systems were compared with the changes in fat concentration during simulated intermittent gavage or bolus feedings. With both mechanical pumps the largest cumulative fat losses and the greatest decreases in fat concentrations occurred at the slowest infusion rates. State of homogenization of the milk generally made little difference in the changes in fat concentration using the syringe pump, whereas homogenizing the milk increased the fat concentration significantly with the roller pump. With the syringe pump the positioning of the syringe tip (horizontal or vertical) made no difference in fat concentration at an infusion rate of 1 ml/hr, whereas at 4 and 7 ml/hr the fat concentration was increased significantly by keeping the syringe tip vertical. With either mechanical pump a large fat bolus was delivered during the eighth and final hour of infusion if the milk remaining in the tubing was recovered by using air infusion at the same infusion rate. Intermittent bolus delivery of human milk resulted in no significant loss of human milk fat, no changes in fat concentration, and no terminal delivery of a large fat load. Thus intermittent bolus feedings are preferred over continuous mechanical pump infusion systems for the delivery of human milk to low-birth-weight infants.