RESUMO
STUDY OBJECTIVE: To determine the effect of the type of dietary protein (3.3 gm/kg per day) on acid-base status, protein nutritional status, plasma amino acid concentrations, and nutrient (nitrogen, fat, mineral, trace element) balance. SUBJECTS: Preterm infants (birth weight less than or equal to 1250 gm, gestational age less than or equal to 32 weeks) with no evidence of systemic disease, who had achieved a minimal enteral intake of 110 kcal/kg per day by 21 days of age. INTERVENTIONS: Each infant was fed three study formulas that differed only with respect to the ratio of whey to casein (60:40, 35:65, 18:82). Each formula was given for 1 week. At the end each week, blood was drawn and a 48-hour balance was determined. MAIN RESULTS: Late metabolic acidosis, uremia, and hyperammonemia were not observed. No differences in pH or serum bicarbonate were noted. Base excess was greater with the casein-predominant formula (18:82 greater than 35:65, 60:40) but remained within normal limits for the preterm infant. Plasma concentrations of threonine (60:40 greater than 35:65 greater than 18:82), phenylalanine, and tyrosine (18:82 greater than 35:65 greater than 60:40) differed. Nitrogen absorption (60:40 less than 35:65, 18:82), nitrogen retention (60:40 less than 35:65, 18:82), fat absorption (60:40, 35:65 greater than 18:82), and phosphorus absorption (60:40 less than 35:65, 18:82) also differed. CONCLUSIONS: At an intake of 3.3 gm/kg per day, the type of dietary protein had little effect on metabolic status. Differences in plasma amino acid concentrations and nutrient balance suggest that a formula containing protein with a whey/casein ratio of 35:65 may be preferable to that with a whey/casein ratio of 60:40 or 18:82 for the very low birth weight infant.
Assuntos
Caseínas/metabolismo , Alimentos Infantis , Recém-Nascido de Baixo Peso/fisiologia , Leite/metabolismo , Equilíbrio Ácido-Base/fisiologia , Aminoácidos/sangue , Animais , Caseínas/administração & dosagem , Humanos , Recém-Nascido de Baixo Peso/crescimento & desenvolvimento , Recém-Nascido de Baixo Peso/metabolismo , Recém-Nascido , Nitrogênio/metabolismo , Estado Nutricional , Fósforo/sangue , Fósforo/metabolismoRESUMO
Adding docosahexaenoic acid (DHA) (22:6n-3) to formulas is more effective than increasing formula alpha-linolenic acid (18:3n-3) in maintaining blood phospholipid DHA levels similar to those in breast-fed infants. However, in long-term trials supplementary DHA given as marine oil reduces blood phospholipid arachidonic acid (AA) in preterm infants. This effect is not seen in short-term trials unless the total n-3 intake from marine oil exceeds 0.5% of the total fatty acids. In addition, there is considerable variability among individual preterm infants in blood phospholipid AA and DHA levels that is not dependent on diet. Within dietary treatments, a significant positive correlation between AA and DHA concentrations suggests that factor(s) other than marine oil supplementation affect both AA and DHA status. Docosahexaenoic acid and AA concentrations in plasma phospholipids are significantly correlated with DHA and AA concentrations in red blood cell phospholipids, suggesting that the observed individual differences in DHA and AA within groups represent true differences in fatty acid status. Preterm infants appear to be vulnerable to a poor status of both DHA and AA; further feeding trials are needed to identify the optimal balance of fatty acids for feeding these infants.
Assuntos
Ácido Araquidônico/sangue , Ácidos Docosa-Hexaenoicos/sangue , Óleos de Peixe/metabolismo , Alimentos Infantis , Recém-Nascido Prematuro/sangue , Óleos de Plantas/metabolismo , Alimentos Fortificados , Humanos , Lactente , Recém-NascidoRESUMO
STUDY OBJECTIVE: To examine (1) the effect of vitamin D intake (380 to 480 IU daily) on plasma 25-hydroxyvitamin D (25-OHD) and 1,25-dihydroxyvitamin D (1,25-(OH)2D) concentrations and (2) the relationship of 1,25-(OH)2D to calcium and phosphorus absorption and retention in the very low birth weight infant receiving a preterm infant formula. SUBJECTS: Eleven "well" infants with a birth weight and gestational age (mean +/- SD) of 1078 +/- 128 gm and 29 +/- 1.9 weeks, respectively, were studied for a 3-week period. Weight and postnatal age (mean +/- SD) at the beginning of the study were 1132 +/- 56 gm and 16 +/- 6 days, respectively. All infants were fed a preterm infant formula and tolerated a full enteral intake (120 kcal/kg/day) for the duration of the study. INTERVENTIONS: Plasma 25-OHD and 1,25-(OH)2D concentrations were measured at the beginning of the study and at the beginning of each 48-hour balance period. Calcium and phosphorus balance studies (n = 33) were performed weekly. MAIN RESULTS: Plasma 25-OHD (30 +/- 10 ng/ml) and 1,25-(OH)2D (54 +/- 14 pg/ml) concentrations were normal at the beginning of the study. Plasma 25-OHD values did not change, but 1,25-(OH)2D values increased (p less than 0.001) throughout the study. Plasma 1,25-(OH)2D concentrations were not related to calcium or phosphorus absorption and retention, but were a linear function of postconceptional age. CONCLUSIONS: Normal vitamin D status and activity are maintained in the very low birth weight infant fed a high calcium formula (380 to 480 IU of vitamin D daily). Plasma 1,25-(OH)2D concentrations are not related to calcium absorption but are linearly related to maturity.