Growth and protein status of term infants fed soy protein formulas differing in protein content

OBJECTIVE

The purpose of this study was to compare growth and protein status of healthy term infants from 2 to 112 days of age fed a commercially available soy-based formula (IS) and a similar formula (EF) containing less protein (2.91 vs 2.45 g/100 kcal).

DESIGN

A controlled, randomized, blind parallel clinical trial was conducted in 32 male and 32 female infants. Infants were enrolled at 2 days of age, and their assigned formula was their only feeding to 112 days of age. At this time their weight, length, and head circumference were measured. Weight, length, and head circumference were measured and formula intake, formula intolerance and stool characteristics were recorded at 8, 28, 56, and 112 days of age. Plasma urea nitrogen (PUN), total protein, albumin, and transthyretin were determined at 56 and 112 days.

RESULTS

There were no statistically significant differences in weight, length, head circumference, or gains in these measures. PUN concentration was significantly lower in infants fed EF than IS at 56 and 112 days. Plasma total protein, albumin, and transthyretin concentrations were not different between the two feeding groups at the two testing periods. Tolerance to the two formulas was similar. Stool characteristics did not differ between the two groups.

CONCLUSION

A soy-based formula containing 2.45 g protein/100 kcal and approximately 640 mumol of total sulfur containing amino acids/100 kcal adequately meets the protein needs of term infants from 2 to 112 days of age.

Growth and metabolic response of premature infants fed whey- or casein-dominant formulas after hospital discharge

We conducted a double-blind, randomized study to test the hypothesis that a whey-dominant formula permits a growth and metabolic advantage over a casein-dominant formula in preterm infants after hospital discharge. Nineteen low birth weight infants were studied for 6 months from the time of discharge. Ten received a casein-dominant formula, and nine received a whey-dominant formula. Growth (weight, length, head circumference, mid-arm circumference, and skin-fold thickness), biochemical measurements (alkaline phosphatase activity, acid-base status, and hemoglobin, serum total protein, albumin, and urea nitrogen levels), and quantity of formula intake did not differ significantly between the groups over a 6-month study period. Serum transthyretin and urea nitrogen concentrations differed significantly between the two feeding groups at the day of entry into the study only. The results indicate that, after hospital discharge, premature infants fed a whey-dominant formula do not differ in growth or biochemical measurements from those fed a casein-dominant formula.

Growth and adiposity of term infants fed whey-predominant or casein-predominant formulas or human milk

Growth, estimated composition of weight gained, and stool patterns of term infants who were fed either a whey-predominant formula or a casein-predominant formula in a random design and of breast-fed infants were compared. All infants (N = 111) were healthy, singleton products of uncomplicated pregnancies. Birth weights and other anthropometric measures in the first few days of life were not different among the three feeding groups. Formula or breast milk was the infants' principal source of energy from birth to age 16 weeks. Average energy intakes of formula-fed infants and change of intakes with age were similar in both groups at all ages. Feeding groups were not significantly different at any age in weight, length, weight or length gain, head circumference, skinfold measurements, upper arm fat area and muscle area, or estimated total body fat. Stools of infants on the whey-predominant formula differed from both the breast-fed and casein-predominant formula groups.

Nutritional balance studies in very-low-birth-weight infants: role of whey formula

Although the optimal type and amount of protein for feeding very-low-birth-weight (VLBW) infants is not well defined, a protein composition with a whey protein to casein ratio of 60/40 is generally considered desirable. This study used the metabolic balance technique to compare nitrogen retention rates in 19 VLBW (less than 1,530 g) infants fed either an experimental whey protein-predominant formula (WPF) containing ultra filtered whey protein or a conventional casein-predominant formula (CPF) containing approximately 20% more protein and more minerals. Blood chemistries and anthropometric measurements were assessed serially. Although infants fed CPF received and retained more protein than infants fed WPF, nitrogen retentions were 73.1 and 74.5% of intake, respectively, and not different between the two feeding groups. The data suggest that proteins from either WPF or CPF are adequately utilized by VLBW infants. Although WPF permitted nitrogen retention rates similar to fetal accretion rates, CPF more nearly met estimated nitrogen requirements of the low-birth-weight infant. Infants fed WPF showed a more favorable course with respect to their metabolic acid-base status, characterized by normal buffer base concentrations and less predisposition to metabolic acidosis. We conclude that whey-predominant protein is preferable to casein-predominant protein in the diet of VLBW neonates because it may lessen the risk of metabolic acidosis and its potential adverse effects.

Survey: methods of feeding low-birth-weight infants

The directors of 269 neonatal intensive care units were surveyed to determine how low-birth-weight infants are being fed. Feeding practices were based on birth weight, with the smallest infants receiving parenteral nutrition for the longest time after birth. First enteral feedings usually were given by the nasogastric route in infants with birth weight of 1,500 g or less, but transpyloric feedings were used in 15% of neonatal intensive care units for infants with birth weight less than 1,000 g. The initial enteral feeding was sterile water in 56% to 58% of the neonatal intensive care units, but was glucose water or milk in the others. Once enteral feeding was established, both human milk from the infant's own mother and commercial formula were used. Whether human milk was mixed or alternated with infant formula, or whether some infants in the nursery were fed human milk while others were fed formula, was not determined. The type of infant formula fed to low-birth-weight infants depended on the infant's birth weight and clinical status. Both human milk and formula were supplemented with energy (fat or carbohydrates) and vitamins, but not with calcium and phosphorus, in most neonatal intensive care units. Some vitamins, such as vitamins A and D, may be oversupplemented, while others, such as folic acid, may be undersupplemented.

Growth and plasma amino acid concentrations in term infants fed either whey-predominant formula or human milk

We found no significant differences in mean growth measurements or mean plasma amino acid concentrations in 14 healthy full-term infants fed a whey-predominant cow milk formula and 15 healthy full-term infants who were breast-fed. Plasma taurine concentrations did not differ despite a tenfold higher level of taurine in human milk versus that in the formula. Plasma amino acid concentrations were measured one hour after feeding when the infants were 3 days and 2, 8, and 16 weeks of age. Weight, length, head circumference, crown-rump length, and skinfold thickness were measured at 3 days, 2 weeks, and 1, 2, 4, and 6 months of age. This study indicates that a whey-predominant cow milk formula compares favorably with human milk as a primary feeding for full-term infants.