A modified cows' milk formula suitable for low birthweight infants

Higher versus lower protein intake in formula-fed low birth weight infants

BACKGROUND

The ideal quantity of dietary protein for formula-fed low birth weight infants < 2.5 kilograms is still a matter of controversy and debate. In premature infants, the protein intake must be sufficient to achieve normal growth without negative effects such as acidosis, uremia, and elevated levels of circulating amino acids (e.g. phenylalanine levels). This systematic review evaluates the benefits and risks of higher (>= 3.0 g/kg/day) versus lower (< 3.0 g/kg/day) protein intakes during the initial hospital stay of formula-fed preterm infants < 2.5 kilograms.

OBJECTIVES

To determine whether higher (>= 3.0 g/kg/day) versus lower (< 3.0 g/kg/day) protein intakes during the initial hospital stay of formula-fed preterm infants < 2.5 kilograms result in improved growth and neurodevelopmental outcomes without evidence of short and long-term morbidity.

SEARCH STRATEGY

Two review authors searched MEDLINE (1966 - May 2005), CINAHL (1982 - May 2005), PubMed (1966 - May 2005), EMBASE (1980 - May 2005), the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 2, 2005), abstracts, conferences and symposia proceedings from Society of Pediatric Research, and American Academy of Pediatrics. Cross references were reviewed independently for additional relevant titles and abstracts for articles up to fifty years old.

SELECTION CRITERIA

Randomized controlled trials contrasting levels of formula protein intakes as low (< 3.0 g/kg/day), high (=> 3.0 g/kg/day but < 4.0 g/kg/day), or very high protein intake (=> 4.0 g/kg/day) during hospitalization of neonates less than 2.5 kilograms at birth who were formula-fed. Studies were not included if infants received partial parenteral nutrition during the study period or were fed formula as a supplement to human milk. Given the small number of studies that met all inclusion criteria, studies in which nutrients other than protein also varied (> 10% relative difference) were added in a post-facto analysis.

DATA COLLECTION AND ANALYSIS

Two review authors used standard methods of the Cochrane Collaboration and of the Cochrane Neonatal Review Group to independently assess trial eligibility and quality, and extracted data. In a 3-arm trial where two groups fell within the same predesignated protein intake group, weighted means and pooled standard deviations were calculated.

MAIN RESULTS

The literature search identified 37 studies, of which five met all the inclusion criteria. All five studies compared low (< 3.0 g/kg/day) to high protein intakes (=> 3.0 g/kg/day but < 4.0 g/kg/day). The overall analysis revealed an improved weight gain (WMD 2.36 g/kg/day, 95% CI 1.31, 3.40) and higher nitrogen accretion (WMD 143.7 mg/kg/day, 95% CI 128.7, 158.8) in infants receiving formula with higher protein content while other nutrients were kept constant. None of the studies reported IQ or Bayley scores at 18 months or later. No significant differences were seen in rates of necrotizing enterocolitis, sepsis or diarrhea. Of three studies included in the post-facto analysis, only one could be included in the meta-analysis. The post-facto analysis revealed further improvement in all growth parameters in infants receiving formula with higher protein content (weight gain: WMD 2.53 g/kg/day, 95% CI 1.62, 3.45, linear growth: WMD 0.16 cm/week, 95% CI 0.03, 0.30, and head growth: WMD 0.23, 95% CI 0.12, 0.35). There was no significant difference (WMD 0.25, 95% CI -0.20, 0.70) in the concentration of plasma phenylalanine between the high and low protein intake groups. One study (Goldman 1969) in the post-facto analysis documented a significantly increased incidence of low IQ scores, below 90, in infants of birth weight less than 1300 grams who received a very high protein intake (6 to 7.2 g/kg/day).

AUTHORS' CONCLUSIONS

This systematic review suggests that higher protein intake (=> 3.0 g/kg/day but < 4.0 g/kg/day) from formula accelerates weight gain. Based on increased nitrogen accretion rates, this most likely indicates an increase in lean body mass. Although accelerated weight gain is considered to be a positive effect, increase in other outcome measures examined may represent a negative or ambivalent effect. These include elevated blood urea nitrogen levels and increased metabolic acidosis. Limited information was available regarding the impact of higher formula protein intakes on long term outcomes such as neurodevelopmental abnormalities. As determined in this review, existing research literature on this topic is not adequate to make specific recommendations regarding the provision of very high protein intake (> 4.0 g/kg/day) from formula.

Validation of the Center for Medicare and Medicaid Services algorithm for eligibility for dialysis

The Center for Medicaid and Medicare Services (CMS) has recently revised their end-stage renal disease (ESRD) Medical Evidence Report, Medicare Entitlement, and Patient Registration CMS 2728 Form. The modified algorithm calls for the use of formulae to estimate glomerular filtration rate (GFR). The new criterion is defined as estimated GFR of less than 20 ml/min per 1.73 m(2). GFR is either estimated by Schwartz formula (C(SCH)) in children or Modification of Diet in Renal Disease formula (C(MDRD)) in adults. The purpose of this communication is to test the validity of the new CMS GFR algorithm in detecting children who need renal replacement therapy. We evaluated two cohorts of children. Group I included single-center data from 626 (125)I-iothalamate clearance studies (C(IO)) that were compared with the simultaneous estimation of GFR by C(SCH). Group II included data on 659 children from the patient incidence registry obtained from the ESRD Network of Texas between February 1996 and October 2003. In group I there were 76 children (76 C(IO)) with C(SCH) less than 20 ml/min per 1.73 m(2) of whom 50 (67%) had C(IO) less than 15 ml/min per 1.73 m(2). Of children with C(IO) less than 15 ml/min per 1.73 m(2), 62% had a C(SCH) less than 20 ml/min per 1.73 m(2). The ability of C(SCH) greater than 20 ml/min per 1.73 m(2 ) to predict C(IO) greater than 15 ml/min per 1.73 m(2 )(negative predictive value) is 0.95. The number of children who were started on dialysis in Texas within the study period was 659 (group II). The mean C(SCH)+/-SD was 10.8+/-7.7 ml/min per 1.73 m(2). Of the patients who were initiated on dialysis, 94% had C(SCH) less than 20 ml/min per 1.73 m(2). The results were sustained when race, gender, age range, and type of diagnosis were considered. The new CMS algorithm provides a good negative predictive estimate of GFR less than 15 ml/min per 1.73 m(2).

Nutrient requirements for preterm infant formulas

Achieving appropriate growth and nutrient accretion of preterm and low birth weight (LBW) infants is often difficult during hospitalization because of metabolic and gastrointestinal immaturity and other complicating medical conditions. Advances in the care of preterm-LBW infants, including improved nutrition, have reduced mortality rates for these infants from 9.6 to 6.2% from 1983 to 1997. The Food and Drug Administration (FDA) has responsibility for ensuring the safety and nutritional quality of infant formulas based on current scientific knowledge. Consequently, under FDA contract, an ad hoc Expert Panel was convened by the Life Sciences Research Office of the American Society for Nutritional Sciences to make recommendations for the nutrient content of formulas for preterm-LBW infants based on current scientific knowledge and expert opinion. Recommendations were developed from different criteria than that used for recommendations for term infant formula. To ensure nutrient adequacy, the Panel considered intrauterine accretion rate, organ development, factorial estimates of requirements, nutrient interactions and supplemental feeding studies. Consideration was also given to long-term developmental outcome. Some recommendations were based on current use in domestic preterm formula. Included were recommendations for nutrients not required in formula for term infants such as lactose and arginine. Recommendations, examples, and sample calculations were based on a 1000 g preterm infant consuming 120 kcal/kg and 150 mL/d of an 810 kcal/L formula. A summary of recommendations for energy and 45 nutrient components of enteral formulas for preterm-LBW infants are presented. Recommendations for five nutrient:nutrient ratios are also presented. In addition, critical areas for future research on the nutritional requirements specific for preterm-LBW infants are identified.

Evaluation of a special low birth weight formula, with and without the use of medium chain triacylglycerols

A special low birth weight formula containing 1.8 g/100 ml of medium chain triacylglycerols (Nenatal) was compared with 'modified' Nenatal (medium chain triacylglycerols (MCT) replaced by long chain triacylglycerols (LCT)) and standard modified baby milk (Cow and Gate Premium). 22 infants of birth weight less than 1500 g and gestational age less than 33 weeks were studied for three weeks when enteral feeds were well tolerated. Nenatal was given to all infants for the first and third weeks, during the middle week 11 infants received Premium and 11 infants received modified Nenatal. On Nenatal there was a significant elevation of serum beta-hydroxybutyrate and small amounts of medium chain fatty acids were detected in the serum. Glucose and long chain triacylglycerol levels were similar on all feeds. Incremental weight gain and energetic efficiency of weight gain was significantly greater on Nenatal than on Premium, but there was no difference in this respect between Nenatal and modified Nenatal. We conclude that the use of a special low birth weight formula is associated with increased weight gain, but this is not dependent on the presence of MCT in the feed. Therefore although feeds containing MCT are well tolerated, there seems little advantage in including MCT in the formulation of low birth weight feeds.

Amino acid and protein requirements in a preterm infant with classic phenylketonuria

A preterm infant with classic phenylketonuria required rather less than 90 mg/kg of phenylalanine and between 270 and 290 mg/kg tyrosine daily to achieve a rate of weight gain of around 20 g/kg per day. Using Lofenalac as the low phenylalanine food, the intake of tyrosine, an essential amino acid for patients with phenylketonuria seemed to be limiting in respect of growth.

The effect of a glucose polymer mixture (caloreen) on stool composition in normal neonates

Stool composition was studied in 10 newborn infants following (a) a modified milk formula (Cow & Gate Premium) and (b) a high energy formula [104 kcal (435 kJ) per 100 ml] in which the additional energy was provided in the form of 10 per cent Caloreen. The only significant difference in stool composition in the Caloreen-fed babies was a lower sodium concentration. The results suggest that the high energy diet did not produce diarrhoea or other changes in the stool composition which might have an adverse effect on the infant.

High volume milk feeds for preterm infants

Fifty nine preterm infants of between 1.0 and 2.0 kg birthweight who were fed 250 ml/kg/day of breast milk or standard formulas gained weight at the intrauterine rate without complications. It is suggested that high volume feeding is a satisfactory alternative to low birthweight formula milks and is more desirable in infants who are to be breast fed.

Double metabolic balances on low birthweight infants fed formulae of differing composition

The comparative nutritional merits of two infant milk formulae, Ready-to-Feed Premium Babyfood (Cow and Gate Ltd.) and Prematalac (Cow and Gate Ltd.) were examined--Prematalac is modified in an attempt to meet the specific requirements of the low birthweight infant. Nine premature infants were enrolled for two metabolic balance periods in a cross-over experimental design. At the onset the infants were randomly allocated one of two milks. Various anthropometric data were collected at the start and end of each 4 day balance. All infants received more energy and protein per kg body weight per day on Prematalac compared with Premium. Incremental weight, though satisfactory for both milks over the balance periods, was greater when Prematalac was fed compared with Premium (mean and (range) 46 (25-93), 19 (9-44) g per day respectively). No differences were detected for gain in length between the two milks. Mean percent digestibility of energy intake was similar for both milks (92%). Infants retained more nitrogen when fed Prematalac compared with Premium (mean (+SD) 477 (59) and 299 (30) mg per kg per day respectively). Neither milk was considered ideal, and we conclude that standard formulae are unable to support the potential for gain in lean body tissue of the premature infant.