Milk protein quality in low birth weight infants: effects of protein-fortified human milk and formulas with three different whey-to-casein ratios on growth and plasma amino acid profiles.

Growth rates (weight, length, and head circumference) and selected biochemical indexes of protein metabolism (serum urea, acid-base status, and plasma amino acid concentrations) were determined in low birth weight (LBW) infants appropriate for gestational age (birth weight less than 1,650 g) fed three formulas differing only in the whey-to-casein ratios: 60/40, 50/50, and 35/65. A group of infants fed exclusively human milk protein (HMP)-fortified human milk was used as a control. All diets provided similar daily protein and energy intakes, which were 3.5 g/kg and 122 kcal/kg in the human milk-fed infants and 3.3 g/kg and 121 kcal/kg in the formula-fed infants. Neither weight gain nor rate of growth in length and head circumference differed between the feeding groups and reached intrauterine or better rates in all groups. Values for serum urea and acid-base status were normal and also did not differ among the groups. At the end of the study, plasma threonine concentrations were significantly higher in all formula-fed infants than in the infants fed human milk. The highest plasma threonine concentration was found in the infants receiving the whey-predominant formula. Plasma concentrations of valine, methionine, and phenylalanine were also significantly higher in all formula-fed groups when compared with the human milk group. Plasma total essential amino acid concentrations were also significantly higher in the formula-fed infants than in the human milk fed. The results show that protein quality does not affect growth rate or biochemical indexes of metabolic tolerance in LBW infants fed adequate protein and energy intakes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Protein supplementation of human milk for the nutrition of VLBW-infants: human milk protein vs. meat protein hydrolysate

In 25 very low birth weight infants appropriate for gestational age the influences of different human milk (HM) preparations on weight gain, gross indices of nitrogen metabolism and energy balance were studied during the second month of postnatal life. HM was fortified either by HM-protein (HMP) or by an enzymatic meat protein hydrolysate (PH) to protein concentrations between 1.5 and 1.7 g/100 ml. The caloric densities of both HM preparations were similar between 62 and 68 kcal/100 ml. There were no differences in weight gain (MM + HMP: 18.6 +/- 3.4 g/kg/day; HM + PH: 16.5 +/- 4.1 g/kg/day), nitrogen retention (HM + HMP: 31.5 +/- 3.1 mmol/kg/day; HM + PH: 30.0 +/- 3.2 mmol/kg/day), and the preprandial estimated essential amino acid profiles between the both feeding groups. In contrast the serum concentrations of alpha-amino-nitrogen 60 minutes postprandially were elevated in the infants fed HM + PH in comparison to the infants fed HM + HMP. This high postprandial amino acid concentrations in serum in the group fed HM + PH were accompanied by increased bile acids concentrations in serum, higher renal amino acid excretion and increased fecal fat losses. The results suggest that due to the more rapid intestinal absorption of amino acids from PH than from HMP the concentrations of amino acids increase postprandially which results in a detectable increase of the newborn cholestasis in these infants. Nevertheless, the scale of these metabolic responses to feeding protein hydrolysates is small and without detectable influences on nitrogen retention or weight gain.     

Individualized protein fortification of human milk for preterm infants: comparison of ultrafiltrated human milk protein and a bovine whey fortifier.

BACKGROUND: To improve the nutritional management of pre-term infants, a new individualized human milk fortification system based on presupplementation milk protein analyses was evaluated. METHODS: In an open, prospective, randomized multicenter study, 32 healthy preterm infants (birth weights, 920-1750 g) were enrolled at a mean of 21 days of age (range, 9-36 days) when tolerating exclusive enteral feedings of 150 ml/kg per day. All infants were fed human milk and were randomly allocated to fortification with a bovine whey protein fortifier (n = 16) or ultrafiltrated human milk protein (n = 16). All human milk was analyzed for protein content before fortification with the goal of a daily protein intake of 3.5 g/kg. During the study period (mean, 24 days) daily aliquots of the fortified milk were obtained for subsequent analyses of the protein content. RESULTS: Both fortifiers were well tolerated, and growth gain in weight, length, and head circumference, as well as final preprandial concentrations of serum urea, transthyretin, transferrin, and albumin were similar in both groups. The ultimate estimated protein intake was equivalent in both groups (mean 3.1+/-0.1 g/kg per day). Serum amino acid profiles were similar in both feeding groups, except for threonine (significantly higher in the bovine fortifier group) and proline and ornithine (significantly higher in the human milk protein group). CONCLUSIONS: Protein analyses of the milk before individual fortification provides a new tool for an individualized feeding system of the preterm infant. The bovine whey protein fortifier attained biochemical and growth results similar to those found in infants fed human milk protein exclusively with the corresponding protein intakes.     

Neonatal nutrition with enriched human milk. EOPROTIN 60 in comparison with human albumin]

The influence of feeding fresh human milk supplemented either with EOPROTIN (n = 13) or human albumin (n = 15) on biochemical parameters and growth were studied in preterm infants with gestational ages below 32 weeks p.m. up to the 42nd day of postnatal life. In both feeding groups the intakes of protein, energy and electrolytes were similar. The serum concentrations of bile acids, alpha-amino-nitrogen and prealbumin, the renal excretion of total nitrogen, alpha-amino-nitrogen, urea and ammonia as well as the growth in weight and length were studied in all infants. The supplementation of the fresh human milk with EOPROTIN results in significant lower serum concentrations of alpha-amino-nitrogen (1.56 +/- 0.21 vs 2.03 +/- 0.27 mmol/l; p less than 0.01), higher serum concentrations of prealbumin (89.8 +/- 20.3 vs 72.7 +/- 13.3 mg/l; p less than 0.02), and lower urinary excretion of total nitrogen (7.4 +/- 0.9 vs 8.9 +/- 1.1 mmol/kg/day); if compared to the results found in the infants fed human albumin supplemented human milk. The higher nitrogen retention in the EOPROTIN than in the human albumin fed infants was associated by a significant higher growth in weight (16.6 +/- 1.4 vs 13.7 +/- 1.9 g/kg/day; p less than 0.01) as well as in length (1.02 +/- 0.08 vs 0.87 +/- 0.1 cm/week; p less than 0.01). The results indicate that the bioavailability of EOPROTIN is higher than that of human albumin. The observed differences in the nutritional response between the two human milk supplements may be based on differences in the amino acids composition which is in EOPROTIN adapted to the nutritional available part of the protein in human milk.     

Growth of very low birth weight infants on varying amounts of human milk protein

In a double-blind, randomized study, 28 healthy, growing very low birth wt, appropriate-for-gestational-age infants were fed human milk, preferably mother's own, fortified daily with human milk protein and/or human milk fat. The infants entered the study when they were stable on complete enteral intakes of 170 mL/kg/d (mean age = 19 d). The study lasted for a mean of 4 wk. Samples from all the milks were collected daily, and intakes of protein, fat, carbohydrates, energy, and electrolytes were calculated weekly during the whole study period. Protein intakes ranged from 1.7 to 3.9 g/kg/d, and energy intakes from 100 to 150 kcal/kg/d. Wt and length gain in the nonprotein-enriched groups were 15.6 +/- 2.7 g/kg/d (mean +/- SD) and 0.88 +/- 0.17 cm/wk; the corresponding figures for the protein-enriched groups were 20.2 +/- 2.1 g/kg/d and 1.24 +/- 0.14 cm/wk. There was a strong correlation between protein intake and growth in wt and length up to an intake of about 3 g/kg/d; more protein did not result in increased growth. The same was true for energy intake, with a maximal growth rate at an intake of about 120 kcal/kg/d. A protein intake of more than 3 g/kg/d resulted in a growth rate equal to or higher than the estimated intrauterine growth rate. Some infants fed mature banked human milk alone had a poor growth. Sodium intake was low, ranging from 1.5 to 2.6 mmol/kg/d. No correlation was found between sodium intake and growth rates.     

Amino acid concentrations in plasma and urine in very low birth weight infants fed protein-unenriched or human milk protein-enriched human milk

Preprandial plasma and urine amino acid concentrations were measured in 28 growing, very low birth weight, appropriate-for-gestational-age infants randomly assigned to either protein-unenriched (n = 14) or human milk protein-enriched (n = 14) human milk. The two groups of infants had similar birth weights (900 to 1500 g) and gestational ages (26 to 32 weeks). The study was initiated at a mean age of 19 days when the infants tolerated full feeding volumes and lasted for a mean time of 28 days. Mean protein intake values were 2.1 +/- 0.3 and 3.6 +/- 0.3 g/kg per day (mean +/- SD) and weight gain values were 26.6 +/- 7.4 and 35.1 +/- 3.6 g/day in the protein-unenriched and the protein-enriched groups of infants, respectively. Human milk protein enrichment resulted in significantly increased concentrations of all plasma amino acids except serine, taurine, and histidine. Most urine amino acid concentrations correlated with protein intake and with the plasma concentrations, suggesting that the effects of protein quality and quantity can be evaluated by measuring urinary amino acid concentrations alone, thereby making such studies less invasive. Infants fed protein-unenriched human milk had growth rates below the estimated intrauterine rate as well as low plasma and urine amino acid concentrations, indicating suboptimal protein intake levels. When the plasma concentrations of the essential amino acids in the protein-enriched infants from the present study were compared with concentrations found in the literature in fetal and umbilical cord plasma, both were found to be much higher.(ABSTRACT TRUNCATED AT 250 WORDS)     

Supplementation with human milk protein improves growth of small premature infants fed human milk

We investigated the influence of human milk protein and medium-chain triglyceride supplementations of human milk feedings on the growth of very low birth weight infants during their first weeks of life. A group of 44 preterm infants with birth weights of less than 1,520 g and a mean gestational age of 30.3 weeks was randomly divided into four groups to receive plain human milk or human milk supplemented with human milk protein (0.9 g/dL), with medium-chain triglycerides (1 g/dL), or with both. The medium-chain triglyceride oil supplementation did not influence the growth of these infants. The infants given supplementary protein gained weight faster during weeks 4 to 6 than those without (18.5 +/- 0.7 v 15.1 +/- 0.6 g/kg/d; mean +/- SEM; P = .001). After 4 weeks of age the infants given supplementary protein had a mean weight gain equal to the mean intrauterine rate, in contrast to the infants of the other groups, who grew more slowly until age 6 weeks. Furthermore, we found a correlation between serum albumin concentration and weight gain during the seventh week of life (P = .018). The length growth velocity for the infants with protein supplementation was 0.99 +/- 0.06 cm/wk (mean +/- SEM) and for those without 0.83 +/- 0.05 cm/wk (P = .043). There was no difference in growth of head circumference between the groups. We conclude that human milk protein supplementation improves the growth of small premature infants fed human milk, and that the protein concentration of bank milk is insufficient for their adequate growth.     

Nutritional balance studies of VLBW infants fed their mothers' milk fortified with a liquid human milk fortifier

This article reports the results of a study designed to compare human milk fortified with a liquid human milk fortifier to a preterm infant formula by analyzing the metabolic balances of certain nutrients when these milks are fed to premature infants. Ten very low birth weight (VLBW) infants were studied during 4-day equilibration periods, then 4-day metabolic balances of N, fat, Ca and P, while each consumed a 1:1 mixture of a pool of its own mother's milk and the liquid human milk fortifier (HM/LF). For comparison, another 10 VLBW infants were studied in similar fashion while consuming the preterm infant formula (PF). Percent nitrogen retentions were 77 +/- 4% (+SD) and 79 +/- 4%, and fat absorptions were 94 +/- 7% and 92 +/- 5% in the HM/LF and PF groups, respectively, and did not differ between the groups. Calcium retention was 86 +/- 21 mg/kg/day (51 +/- 12%) in the HM/LF group and 104 +/- 43 mg/kg/day (45 +/- 19%) in the PF group. The percent Ca retentions did not differ. Phosphorus retentions were 56 +/- 7 mg/kg/day (67 +/- 9%) and 77 +/- 18 mg/kg/day (61 +/- 14%) in the HM/LF and PF groups, respectively. Increases in weight, length, and occipitofrontal circumference (OFC) were similar and normal in both groups. We conclude that VLBW infants fed the HM/LF, mixed 1:1 with their mothers' milk, had rates of absorption and retention of Ca, P, N, and fat similar to rates found in the concurrent study of VLBW infants fed a commercially available PF.     

Supplementation of pooled human milk with casein hydrolysate: energy and nitrogen balance and weight gain composition in very low birth weight infants

Growth and nitrogen and energy balances were studied with a combined technique of nutrient balance and indirect calorimetry measurement in two groups of eight very low birth weight infants fed pooled pasteurized human milk (HM) or cow's milk casein hydrolysate supplemented HM (HM-Pr). There was no difference in the amount of energy absorbed (91 +/- 17 kcal/kg/day with HM-Pr versus 95 +/- 8 with HM-P) or in the growth rate. The infants fed HM-Pr had a higher nitrogen intake (602 +/- 80 versus 395 +/- 64 mg/kg/day; p less than 0.001), urinary nitrogen excretion (160 +/- 64 versus 78 +/- 16 mg/kg/day; p less than 0.005) and nitrogen retention (326 +/- 32 versus 252 +/- 48 mg/kg/day; p less than 0.01). They also had increased plasma concentrations of essential amino acids, urea nitrogen, and total protein without metabolic imbalance. Energy expenditure was higher (58 versus 49 kcal/kg/day; p less than 0.005) and energy storage lower (33 versus 47 kcal/kg/day; p less than 0.05) with HM-Pr. In percent of weight gain, protein and fat accretion represented 12 and 14% in HM-Pr group versus 10 and 27% in HM group. Very low birth weight infants fed casein hydrolysate supplemented pooled HM achieved a growth rate and a weight gain composition similar to the fetus.     

Evidence for functional immaturity of the ornithine-urea cycle in very-low-birth-weight infants

In a randomized, prospective study the response of serum urea concentration to different protein intakes was studied in two groups of preterm infants with different gestational ages on the 8th and the 21st day of life. 16 very-low-birth-weight (VLBW) infants (GA: 29-31 weeks) and 17 low-birth-weight (LBW) infants (GA: 31-33 weeks) were fed either with fresh human milk or with fortified human milk. The protein intake varied between 2.1 and 3.3 g/kg/day. On the 8th day of life the VLBW infants did not respond to higher protein intakes by increased serum urea concentrations, although a clear correlation was found between protein intake and serum alpha-amino-nitrogen concentrations in these infants. The more mature LBW infants responded to a high protein intake by increased serum urea concentrations on the 8th day of life. On the 21st day of life protein intake correlated to both serum urea and alpha-amino-nitrogen concentrations in all infants studied. These findings are consistent with a somewhat limited capacity of the immature infant for expansion of urea production for some time after birth. This immaturity should be considered when metabolic responses to protein intake are studied and evaluated in such infants.     

Indices of protein metabolism in term infants fed either human milk or formulas with reduced protein concentration and various whey/casein ratios

Hyperaminoacidemia is evident in infants fed either whey-dominant or casein-dominant formula containing 2.2 g protein/100 kcal. We assessed protein metabolism in infants fed formulas with reduced protein contents and various whey/casein ratios. Term infants (n = 40) received either human milk or formula containing 1.8 g protein/100 kcal and whey/casein ratios 18:82, 34:66, or 50:50. At ages 4 and 8 weeks, growth indices and mean serum concentrations of retinol binding protein, albumin, total protein, and serum urea nitrogen were similar, as were mean plasma concentrations of total amino acids, total essential amino acids, and their ratio. Compared with infants fed human milk, those fed formula had plasma concentrations similar for valine, lysine, arginine, tyrosine, histidine, threonine, and free and total cyst(e)ine; elevated for phenylalanine, methionine, and citrulline; and depressed for taurine and tryptophan. Except for leucine, mean plasma amino acid values varied similarly among formula groups despite differences in intakes. Our data indicate that feeding formulas providing 1.8 g protein/100 kcal results in many indices of protein metabolism characteristic of human milk feeding. However, certain differences are noted, suggesting the need for further manipulation of specific amino acid patterns of infant formulas.     

Growth and plasma amino acid concentrations in very low birthweight infants fed either human milk protein fortified human milk or a whey-predominant formula

In a prospective, study involving 20 VLBW-infants (AGA), divided into two study groups of 10 infants, we have evaluated the effects on growth and metabolism of human milk fortified with ultrafiltrated human milk protein and a whey-predominant (whey/casein = 60/40) formula containing 2 g/dl of protein. The study was initiated at a mean age of 30 days when an oral intake of 180 ml/kg/d was tolerated and continued until a weight of 2 kg was reached. The protein intake in both groups was about 3.7 g/kg/d. All infants in both groups reached intrauterine rates of growth for the age, weight gain 18.0 g/kg/d, and length 1.2 cm/week. BUN, acid-base status, total protein and albumin were normal and similar in the two groups. Plasma levels of threonine, glycine, citrulline and methionine were significantly greater in the formula-fed infants. Taurine and proline had higher concentrations in the protein fortified human milk group. There was good tolerance of protein from both sources but the differences in plasma amino acid profiles suggest that the dietary protein quality in formulas for preterm infants must be further modified, if the goal of formula feeding is to achieve metabolic indices of protein metabolism similar to those found when human milk protein is used.     

Plasma amino acid differences in very low birth weight infants fed either human milk or whey-dominant cow milk formula

Midmorning plasma amino acid levels were measured in 31 healthy, very low birth weight infants (mean age 16 days, mean birth weight 1180 g, gestation 29 wk) during 96-h balance studies. All infants received continuous enteral infusion of isonitrogenous, isocaloric preparations of either human milk fortified with pasteurized, lyophilized fractions of mature human milk (n = 18) or whey-dominant cow milk-based formula (n = 13). Weight gain (15 g/kg/day), nitrogen retention (303 mg/kg/day), and metabolizable energy (104 kcal/kg/day) were similar between groups. Plasma levels of threonine, valine, and the sum of essential amino acids were significantly greater in the whey-dominant formula-fed infants (p less than 0.01). Taurine and cystine were measured in significantly greater concentrations in the fortified human milk and threonine, valine, methionine, and lysine in the whey-dominant cow milk formula (p less than 0.01). Relationships between plasma amino acid levels and indices of nitrogen utilization differed between groups. These differences suggest that further modifications of whey-dominant formulas may be indicated.     

Nitrogen and fat balances in very low birth weight infants fed human milk fortified with human milk or bovine milk protein

The study was designed to compare two different human milk fortifiers in a group of very low birth weight (VLBW) infants by analysing nitrogen and fat balances, serum concentrations of alpha-amino-nitrogen, urea, and prealbumin as well as growth rates when human milk enriched with one of the two studied fortifiers was fed to the infants. Fortifier A contained different bovine proteins, peptides and amino acids and had an amino acid composition comparable to that of the nutritional available proteins in human milk, with carbohydrates, and minerals. Fortifier B was composed of freeze-dried skimmed human milk and minerals to achieve a similar macronutrient composition in both fortifiers.Eleven infants were fed with human milk enriched with fortifier A and 13 with fortifier B. After a 10-day equilibration period, a 3-day metabolic balance was performed. On the 14th day of the study blood was obtained preprandially for serum analysis and growth rates were estimated. The nitrogen absorption rate (93.8% vs 93.5%) as well as the retention rate (80.8% vs 78.5%) were no different between the groups. The fat absorption rate (92.3% vs 91.5%) as well as the weight gain (32.1 vs 31.1 g/day) were similar and there were no differences in the serum parameters studied. The results indicate that feeding VLBW infants with human milk enriched with a well-balanced bovine fortifier fulfil their nutritional requirements as well as diets composed exclusively of human milk protein.     

Vitamin K status of lactating mothers, human milk, and breast-feeding infants

Hemorrhagic disease of the newborn is a disease of breast-feeding newborns. There is little information on longitudinal breast milk concentrations of phylloquinone (vitamin K1) or the effects of maternal phylloquinone supplements on breast milk. In study part 1, 11 lactating mothers, who received 20 mg of phylloquinone orally, had rises in plasma (less than 1 to 64.2 +/- 31.5 ng/mL by 6 hours) and breast milk concentrations (from 1.11 +/- 0.82 to 130 +/- 188 ng/mL by 12 hours). In part 2, 23 lactating mothers and their infants were observed longitudinally along with a formula-fed control group of infants (n = 11). Mean breast milk concentrations of phylloquinone at 1, 6, 12, and 26 weeks were 0.64 +/- 0.43, 0.86 +/- 0.52, 1.14 +/- 0.72, and 0.87 +/- 0.50 ng/mL, respectively, in the infants fed human milk. Maternal phylloquinone intakes (72-hour dietary recalls) exceeded the recommended daily allowance of 1 microgram/kg per day. Infant phylloquinone intakes did not achieve the recommended daily allowance of 1 microgram/kg per day in any infant. Plasma phylloquinone concentrations in the infants fed human milk remained extremely low (mean less than 0.25 ng/mL) throughout the first 6 months of life compared with the formula-fed infants (4.39 to 5.99 ng/mL). In this small sample, no infant demonstrated overt vitamin K deficiency. Despite very low plasma phylloquinone concentrations, vitamin K supplements (other than in the immediate newborn period) cannot be recommended for exclusively breast-fed infants based on these data.     

Formula with reduced protein content: effects on growth and protein metabolism during weaning

A total of 20 healthy term infants between 4 and 6 months of age were randomly assigned to either a low protein formula (F1.3) containing 1.3 g protein/100 ml or a high protein formula (F1.8) containing 1.8 g protein/100 ml. Both formulas were isocaloric (72 kcal/100 ml) and had a whey-casein ratio of 50:50. Ten control infants were breast-fed (BF). The mean protein intakes (including supplementary foods) were 1.9 +/- 0.3, 2.6 +/- 0.2, and 1.3 +/- 0.2 g/kg/day, respectively. The mean concentrations of serum urea were 2.8 +/- 0.6 (F1.3), 4.1 +/- 0.6 (F1.8), and 2.2 +/- 0.8 mmol/liter (BF) at 6 months (F1.3 versus BF, NS, F1.8 versus BF, p less than 0.001). The urine excretion of nitrogen was similar in the F1.3 and BF groups being 81 and 78 mg/kg/day. In the F1.8-group nitrogen excretion was higher, 138 mg/kg/day. Plasma concentrations of albumin, prealbumin, and transferrin were normal and similar in the groups. Weight gain was significantly higher in the F1.8 group, 22.8 +/- 1.7 g/kg/wk when compared to the F1.3 and BF groups, 19.9 +/- 3.9 and 18.0 +/- 4.3 (p less than 0.01), respectively. These data indicate that a decreased protein-intake from formula during weaning results in many indices of protein metabolism and growth more similar to those found in BF infants than when conventional follow-up formulas are used.     

Protein quality of human milk fortifier in low birth weight infants: Effects on growth and plasma amino acid profiles

Serum preprandial essential amino acid, urea and prealbumin concentrations, and growth rates were studied in appropriate for gestational age low birth weight infants fed one of three regimens: (1) human milk enriched with human milk protein (n=17); (2) bovine whey protein hydrolysate (n=18; and (3) a mixture of bovine proteins, peptides and amino acids designed to have an amino acid composition close to that of human milk proteins (n=18). Energy and nitrogen intakes were similar in all groups. Growth rates and gross metabolic responses did not differ between the feeding groups. There were also no differences in the amino acid profiles between those infants fed human milk protein fortifier and mixed bovine protein fortifier. Infants fed the whey fortifier had significantly higher threonine concentrations in comparison to those fed exclusively human milk protein (287±63 mol/l vs 168±26 mol/l) whereas the levels of some other essential amino acids (i.e. valine, leucine, lysine, histidine, phenylalanine and tryptophan) were lower. The results indicate that growth rates and gross metabolic indices do not depend on the protein quality of human milk fortifiers. However, the addition of well balanced mixtures of bovine proteins to human milk results in amino acid profiles similar to those observed in LBW infants fed similar amounts of human milk proteins.     

Amino Acid Levels in the Critically ill Preterm Infant Given Mother's Milk Fortified with Protein from Human or Cow's Milk

ABSTRACT. Twenty preterm infants undergoing neonatal intensive care were randomly allocated to one of two feeding regimens: human milk enriched with either human milk protein (HMP) or adapted cow's milk protein (CMP). The birthweights (1076 ± 301 g; 1031 ± 309 g) and the gestational ages (28.4 ± 1.6 weeks; 27.7 ± 2.1 weeks) were comparable. The amount of protein added to the milk was set at 0.7 g/100 ml in order to provide a total supply of 3.0-3.5 g/kg/24 h. All infants received additional amounts of carbohydrate, calcium, phosphorous, and sodium chloride. Capillary whole blood amino acids were measured with high pressure liquid chromatography (HPLC). The amino acid levels did not differ significantly when the feeding groups were compared week by week, but the glycine/valine ratio was higher (p<0.05) in the HMP group after three weeks of fortification. Longitudinal changes after protein enrichment could be demonstrated in both groups. Alanine and threonine increased after one week (p<0.01) in both groups. Glycine in the HMP group peaked after two weeks (p<0.02), and valine in the CMP group increased (p<0.02) after one week on the feeding regimen. However, the amino acids never reached levels above those seen after a meal in normal term newborns. Other variables related to protein intake, such as protein and urea in serum, did not vary between the groups. Growth, expressed as gains in weight, length, and head circumference was poor but comparable. The quality of the protein, whether a human milk protein isolate or a cow's milk whey protein product, used for the fortification of human milk up to a protein load of 3.0-3.5 g/kg/24 h, did not cause any alterations of significance in the amino acid profiles of peripheral blood.     

Pediatric parenteral amino acid mixture in low birth weight infants

A mixture of amino acids designed to maintain normal plasma amino acid concentrations in infants and children requiring parenteral nutrition was evaluated in 28 low birth weight (LBW) infants (birth weight, 750 to 1750 g; postnatal age, 1 to 4 weeks) who required parenteral nutrients for optimal nutritional management. Sixteen babies received only parenteral nutrients for five to 21 days. Ten of these received a typical regimen by peripheral vein (1.91 +/- 0.16 g/kg/d of amino acids and 44.7 +/- 4.4 kcal/kg/d) and six received a typical regimen through a central vein (2.39 +/- 0.11 g/kg/d of amino acids and 95.9 +/- 14.5 kcal/kg/d). Mean weight gain of the peripheral vein subgroup was 10.3 +/- 10.6 g/kg/d; mean nitrogen balance was 230 +/- 66 mg/kg/d. Both the mean rate of weight gain (17.2 +/- 5.1 g/kg/d) and the mean rate of nitrogen retention (267 +/- 49 g/kg/d) of the central vein subgroup were similar to intrauterine rates. In these two subgroups as well as the total population, plasma concentrations of all amino acids except phenylalanine were within the 95% confidence limits of the plasma concentrations observed in LBW infants fed sufficient amounts of human milk to result in a rate of weight gain similar to the intrauterine rate. However, although plasma tyrosine and cyst(e)ine concentrations were within the 95% confidence limits of the plasma concentrations goals, the LBW infant's ability to use N-acetyl-L-tyrosine and cysteine HCl appears to be even less than that of the term infant and older child. In toto, these data support the efficacy of the amino acid mixture evaluated for LBW infants. Of equal importance, they suggest that the LBW infant's ability to use parenterally delivered amino acids is not as limited as commonly thought.     

Bone mineralization in preterm infants fed human milk with and without mineral supplementation

The bone mineral status of healthy preterm infants fed maternal milk was compared with that of similar infants fed maternal milk with mineral supplementation. Fifty infants with birth weight less than 1600 g were fed human milk for 1 week until reaching an intake of 120 kcal/kg/d. Thereafter, infants were assigned randomly to one of three diets: (1) continued unsupplemented human milk, providing an intake of 40 to 50 mg/kg/d calcium and 23 to 30 mg/kg/d phosphorus; (2) human milk mixed with a high mineral containing formula, providing total intakes of 130 mg/kg/d calcium and 68 mg/kg/d phosphorus; or (3) human milk alone for 1 additional week, followed by human milk mixed with a powdered fortifier, providing total intakes of 160 mg/kg/d calcium and 90 mg/kg/d phosphorus. Infants fed human milk with formula supplementation, but not those fed human milk with fortifier, had significantly higher serum phosphorus concentrations and significantly lower serum alkaline phosphatase concentrations than did those fed unsupplemented human milk (P less than 0.01). Bone mineral content of the humerus, determined by photon absorptiometry, however, was similar in all three groups; values averaged 0.104 g/cm at the beginning of the study, and remained unchanged irrespective of mineral supplementation. Shortly before hospital discharge, study diets were discontinued and infants were fed standard proprietary formula or were nursed by their mothers. At 44 weeks postconceptional age (7 to 10 weeks after change in diet), infants were reexamined. Serum phosphorus concentrations increased, serum alkaline phosphatase concentrations decreased, and bone mineral content more than doubled to values comparable with those in term infants. Results at follow-up were comparable for all three initial diet groups and for infants who were formula-fed or breast-fed after hospital discharge. The lack of any significant effect of early maternal milk supplementation on bone mineralization by 44 weeks postconceptional age suggests that these methods of supplementation of maternal milk may not be warranted for healthy preterm infants.