Nutrient accretion in preterm infants fed formula with different protein:energy ratios

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 is still a matter of debate. Protein intake must be sufficient to achieve normal growth without leading to negative effects such as acidosis, uremia, and elevated levels of circulating amino acids.

OBJECTIVES

To determine whether higher (≥ 3.0 g/kg/d) versus lower (< 3.0 g/kg/d) protein intake during the initial hospital stay of formula-fed preterm infants or low birth weight infants (< 2.5 kilograms) results in improved growth and neurodevelopmental outcomes without evidence of short- or long-term morbidity. Specific objectives were to examine the following comparisons of interventions and to conduct subgroup analyses if possible. 1. Low protein intake if the amount was less than 3.0 g/kg/d. 2. High protein intake if the amount was equal to or greater than 3.0 g/kg/d but less than 4.0 g/kg/d. 3. Very high protein intake if the amount was equal to or greater than 4.0 g/kg/d.

SEARCH METHODS

We used the standard search strategy of Cochrane Neonatal to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2019, Issue 8), in the Cochrane Library (August 2, 2019); OVID MEDLINE Epub Ahead of Print, In-Process & Other Non-Indexed Citations, Ovid MEDLINE(R) Daily, and Ovid MEDLINE(R) (to August 2, 2019); MEDLINE via PubMed (to August 2, 2019) for the previous year; and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) (to August 2, 2019). We also searched clinical trials databases and the reference lists of retrieved articles for randomized controlled trials (RCTs) and quasi-randomized trials.

SELECTION CRITERIA

We included RCTs contrasting levels of formula protein intake as low (< 3.0 g/kg/d), high (≥ 3.0 g/kg/d but < 4.0 g/kg/d), or very high (≥ 4.0 g/kg/d) in formula-fed hospitalized neonates weighing less than 2.5 kilograms. We excluded studies if infants received partial parenteral nutrition during the study period, or if infants were fed formula as a supplement to human milk.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures expected by Cochrane and the GRADE approach to assess the certainty of evidence.

MAIN RESULTS

We identified six eligible trials that enrolled 218 infants through searches updated to August 2, 2019. Five studies compared low (< 3 g/kg/d) versus high (3.0 to 4.0 g/kg/d) protein intake using formulas that kept other nutrients constant. The trials were small (n = 139), and almost all had methodological limitations; the most frequent uncertainty was about attrition. Low-certainty evidence suggests improved weight gain (mean difference [MD] 2.36 g/kg/d, 95% confidence interval [CI] 1.31 to 3.40) and higher nitrogen accretion in infants receiving formula with higher protein content (3.0 to 4.0 g/kg/d) versus lower protein content (< 3 g/kg/d), while other nutrients were kept constant. No significant differences were seen in rates of necrotizing enterocolitis, sepsis, or diarrhea. We are uncertain whether high versus low protein intake affects head growth (MD 0.37 cm/week, 95% CI 0.16 to 0.58; n = 18) and length gain (MD 0.16 cm/week, 95% CI -0.02 to 0.34; n = 48), but sample sizes were small for these comparisons. One study compared high (3.0 to 4.0 g/kg/d) versus very high (≥ 4 g/kg/d) protein intake (average intakes were 3.6 and 4.1 g/kg/d) during and after an initial hospital stay (n = 77). Moderate-certainty evidence shows no significant differences in weight gain or length gain to discharge, term, and 12 weeks corrected age from very high protein intake (4.1 versus 3.6 g/kg/d). Three of the 24 infants receiving very high protein intake developed uremia.

AUTHORS' CONCLUSIONS

Higher protein intake (≥ 3.0 g/kg/d but < 4.0 g/kg/d) from formula accelerates weight gain. However, limited information is available regarding the impact of higher formula protein intake on long-term outcomes such as neurodevelopment. Research is needed to investigate the safety and effectiveness of protein intake ≥ 4.0 g/kg/d.

Lactational Stage of Pasteurized Human Donor Milk Contributes to Nutrient Limitations for Infants

BACKGROUND

Mother's own milk is the first choice for feeding preterm infants, but when not available, pasteurized human donor milk (PDM) is often used. Infants fed PDM have difficulties maintaining appropriate growth velocities. To assess the most basic elements of nutrition, we tested the hypotheses that fatty acid and amino acid composition of PDM is highly variable and standard pooling practices attenuate variability; however, total nutrients may be limiting without supplementation due to late lactational stage of the milk.

METHODS

A prospective cross-sectional sampling of milk was obtained from five donor milk banks located in Ohio, Michigan, Colorado, Texas-Ft Worth, and California. Milk samples were collected after Institutional Review Board (#07-0035) approval and informed consent. Fatty acid and amino acid contents were measured in milk from individual donors and donor pools (pooled per Human Milk Banking Association of North America guidelines). Statistical comparisons were performed using Kruskal-Wallis, Spearman's, or Multivariate Regression analyses with center as the fixed factor and lactational stage as co-variate.

RESULTS

Ten of the fourteen fatty acids and seventeen of the nineteen amino acids analyzed differed across Banks in the individual milk samples. Pooling minimized these differences in amino acid and fatty acid contents. Concentrations of lysine and docosahexaenoic acid (DHA) were not different across Banks, but concentrations were low compared to recommended levels.

CONCLUSIONS

Individual donor milk fatty acid and amino acid contents are highly variable. Standardized pooling practice reduces this variability. Lysine and DHA concentrations were consistently low across geographic regions in North America due to lactational stage of the milk, and thus not adequately addressed by pooling. Targeted supplementation is needed to optimize PDM, especially for the preterm or volume restricted infant.

High-protein formulas: evidence for use in preterm infants

Relatively high amounts of protein are required to achieve normal fractional protein synthetic rates during the late second through early third trimester of fetal growth. Once preterm infants achieve higher protein intakes for sustained periods, growth begins to approximate that of the normally growing fetus and long-term neurodevelopmental outcomes are improved. Preterm formulas have been developed that are enriched in protein. This review discusses several factors when using standard preterm formulas and high-protein preterm formulas in the neonatal intensive care unit, with an emphasis on quantity and quality of enteral protein delivery and risks to insufficient and/or excess protein administration.

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 is still a matter of debate. Protein intake must be sufficient to achieve normal growth without negative effects such as acidosis, uremia, and elevated levels of circulating amino acids.

OBJECTIVES

To determine whether higher (≥ 3.0 g/kg/d) versus lower (< 3.0 g/kg/d) protein intake during the initial hospital stay of formula-fed preterm infants or low birth weight infants (< 2.5 kilograms) results in improved growth and neurodevelopmental outcomes without evidence of short- and long-term morbidity.To examine the following distinctions in protein intake. 1. Low protein intake if the amount was less than 3.0 g/kg/d. 2. High protein intake if the amount was equal to or greater than 3.0 g/kg/d but less than 4.0 g/kg/d. 3. Very high protein intake if the amount was equal to or greater than 4.0 g/kg/d.If the reviewed studies combined alterations of protein and energy, subgroup analyses were to be carried out for the planned categories of protein intake according to the following predefined energy intake categories. 1. Low energy intake: less than 105 kcal/kg/d. 2. Medium energy intake: greater than or equal to 105 kcal/kg/d and less than or equal to 135 kcal/kg/d. 3. High energy intake: greater than 135 kcal/kg/d.As the Ziegler-Fomon reference fetus estimates different protein requirements for infants based on birth weight, subgroup analyses were to be undertaken for the following birth weight categories. 1. < 800 grams. 2. 800 to 1199 grams. 3. 1200 to 1799 grams. 4. 1800 to 2499 grams.

SEARCH METHODS

The standard search methods of the Cochrane Neonatal Review Group were used. MEDLINE, CINAHL, PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials (CENTRAL; The Cochrane Library) were searched.

SELECTION CRITERIA

Randomized controlled trials contrasting levels of formula protein intake as low (< 3.0 g/kg/d), high (≥ 3.0 g/kg/d but < 4.0 g/kg/d), or very high (≥ 4.0 g/kg/d) in formula-fed hospitalized neonates weighing less than 2.5 kilograms were included. Studies were excluded if infants received partial parenteral nutrition during the study period or were fed formula as a supplement to human milk. Studies in which nutrients other than protein also varied were added in a post-facto analysis.

DATA COLLECTION AND ANALYSIS

The standard methods of the Cochrane Neonatal Review Group were used.

MAIN RESULTS

Five studies compared low versus high protein intake. Improved weight gain and higher nitrogen accretion were demonstrated in infants receiving formula with higher protein content while other nutrients were kept constant. No significant differences were seen in rates of necrotizing enterocolitis, sepsis, or diarrhea.One study compared high versus very high protein intake during and after an initial hospital stay. Very high protein intake promoted improved gain in length at term, but differences did not remain significant at 12 weeks corrected age. Three of the 24 infants receiving very high protein intake developed uremia.A post-facto analysis revealed further improvement in all growth parameters in infants receiving formula with higher protein content. No significant difference in the concentration of plasma phenylalanine was noted between high and low protein intake groups. However, one study (Goldman 1969) documented a significantly increased incidence of low intelligence quotient (IQ) scores among infants of birth weight less than 1300 grams who received a very high protein intake (6 to 7.2 g/kg).

AUTHORS' CONCLUSIONS

Higher protein intake (≥ 3.0 g/kg/d but < 4.0 g/kg/d) from formula accelerates weight gain. However, limited information is available regarding the impact of higher formula protein intake on long-term outcomes such as neurodevelopmental abnormalities. Available evidence is not adequate to permit specific recommendations regarding the provision of very high protein intake (> 4.0 g/kg/d) from formula during the initial hospital stay or after discharge.

Zinc and copper requirements in preterm infants: an examination of the current literature

BACKGROUND

Zinc and copper are essential for preterm infants, but recommended requirements from different groups vary widely. Recommended zinc intakes have steadily increased over the years. Although this would be expected to impair copper absorption, recommended copper intakes have not risen in parallel.

OBJECTIVES

To systematically review the literature on zinc and copper retention in preterm infants; to examine the effect on zinc intake on copper retention; and to estimate the zinc and copper intakes required to meet the levels of zinc and copper retention required for normal growth.

DESIGN

Studies reporting zinc and/or copper retention in preterm infants (<36 weeks of gestation) during the first 120 days of life were identified using PubMed. Only studies reporting net retention were included.

RESULTS

Fourteen studies on zinc retention reporting data on 45 different groups were identified. Eleven studies (32 groups) were identified reporting copper retention. Zinc retention was significantly higher at higher zinc intakes, and higher in formula-based diets than in human milk based diets. Zinc intakes of between 1.8-2.4 mg/kg/d (from formula based diets) and 2.3-2.4 mg/kg/d (from human-milk based diets) were required to achieve adequate zinc retention. Copper retention was significantly positively correlated with copper intake and significantly negatively correlated with zinc intake. At the zinc intakes suggested previously (1.8-2.4, 2.3-2.4 mg/kg/d), copper intakes of between 200 and 250 mcg/kg/d are required to ensure adequate copper retention.

CONCLUSIONS

Our results support the higher zinc intakes recommended in recent guidelines. However, they suggest that recommended copper intakes have not kept pace with increasing zinc intakes, and that preterm infants may need higher copper intakes than currently recommended.

From parenteral to enteral nutrition: a nutrition-based approach for evaluating postnatal growth failure in preterm infants

BACKGROUND

Nutrition practices for preterm infants include phases of parenteral nutrition (PN), full enteral nutrition (EN), and the transitional phase in between. Our aim was to identify the nutrition phases during which infants are most likely to exhibit poor growth that would affect risk for growth failure (GF) at discharge and to examine factors associated with GF.

METHODS

A retrospective chart review was conducted on infants born <32 weeks' gestation. The neonatal intensive care unit stay was divided into 3 nutrition phases: (1) full PN, (2) transitional PN + EN, and (3) full EN. Weekly growth rates were calculated, and for each growth velocity <10 g/kg/d, the coinciding phase was recorded. GF was defined as a discharge weight below the 10th percentile. The nutrition phases during which growth inadequacy predicted GF at discharge were determined, correcting for other clinical factors associated with GF.

RESULTS

In total, 156 eligible infants were identified. Seventy-six infants (49%) were discharged with weights <10%. Incidence of poor growth was highest during the transitional phase (46%) and was predictive of GF when adjusted for gestational age, birth weight, and severity of illness. Although energy intakes during the transitional phase were comparable to baseline parenteral provision, protein intakes progressively decreased ( P < .0001), consistently providing 3 g/kg/d as PN was weaned. Serum urea nitrogen also declined and was correlated with protein intake (r = -0.32, P < .001).

CONCLUSION

Growth was compromised during the transitional phase, likely related to decreased protein intake. Optimizing protein provision while PN is weaned is an important strategy to prevent postnatal growth failure.

Selected macro/micronutrient needs of the routine preterm infant

Requirements for optimal nutrition, especially for micronutrients, are not well defined for premature infants. The "reference fetus," developed by Ziegler et al,(1) has served as a model to define nutritional needs and studies designed to determine nutrient requirements. Revision of nutrient requirements and provision of optimal nutrition may lead to improved outcomes in preterm infants. Appropriate provision of nutrients also may help prevent nutritional disorders, such as metabolic bone disease and anemia. In this review, we discuss calcium, phosphorus, magnesium, vitamin D, iron, and copper, and define optimal intakes based on the available published data.

The effects of varying protein and energy intakes on the growth and body composition of very low birth weight infants

Objective

To determine the effects of high dietary protein and energy intake on the growth and body composition of very low birth weight (VLBW) infants.

Study design

Thirty-eight VLBW infants whose weights were appropriate for their gestational ages were assessed for when they could tolerate oral intake for all their nutritional needs. Thirty-two infants were included in a longitudinal, randomized clinical trial over an approximate 28-day period. One control diet (standard preterm formula, group A, n = 8, 3.7 g/kg/d of protein and 129 kcal/kg/d) and two high-energy and high-protein diets (group B, n = 12, 4.2 g/kg/d and 150 kcal/kg/d; group C, n = 12, 4.7 g/kg/d and 150 kcal/kg/d) were compared. Differences among groups in anthropometry and body composition (measured with bioelectrical impedance analysis) were determined. An enriched breast milk group (n = 6) served as a descriptive reference group.

Results

Groups B and C displayed greater weight gains and higher increases in fat-free mass than group A.

Conclusion

An intake of 150 kcal/kg/d of energy and 4.2 g/kg/d of protein increases fat-free mass accretion in VLBW infants.

Formula milk versus donor breast milk for feeding preterm or low birth weight infants

BACKGROUND

When sufficient maternal breast milk is not available, the alternative sources of enteral nutrition for preterm or low birth weight infants are donor breast milk or artificial formula milk. Feeding preterm or low birth weight infants with formula milk might increase nutrient input and growth rates. However, since feeding with formula milk may be associated with a higher incidence of feeding intolerance and necrotising enterocolitis, this may adversely affect growth and development.

OBJECTIVES

To determine the effect of formula milk compared with donor human breast milk on growth and development in preterm or low birth weight infants.

SEARCH STRATEGY

The standard search strategy of the Cochrane Neonatal Review Group was used. This included electronic searches of the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 2, 2007), MEDLINE (1966 - May 2007), EMBASE (1980 - May 2007), CINAHL (1982 - May 2007), conference proceedings, and previous reviews.

SELECTION CRITERIA

Randomised controlled trials comparing feeding with formula milk versus donor breast milk in preterm or low birth weight infants.

DATA COLLECTION AND ANALYSIS

Data were extracted using the standard methods of the Cochrane Neonatal Review Group, with separate evaluation of trial quality and data extraction by two reviewer authors, and synthesis of data using relative risk, risk difference and weighted mean difference.

MAIN RESULTS

Eight trials fulfilled the inclusion criteria. Only one trial used nutrient-fortified donor breast milk. Enteral feeding with formula milk compared with donor breast milk resulted in higher rates of growth in the short term. There was no evidence of an effect on long-term growth rates or neurodevelopmental outcomes. Meta-analysis of data from five trials demonstrated a statistically significantly higher incidence of necrotising enterocolitis in the formula fed group: typical relative risk 2.5 (95% confidence interval 1.2, 5.1); typical risk difference: 0.03 (95% confidence interval 0.01, 0.06; number needed to harm: 33 (95% confidence interval 17, 100).

AUTHORS' CONCLUSIONS

In preterm and low birth weight infants, feeding with formula milk compared with donor breast milk results in a higher rate of short-term growth but also a higher risk of developing necrotising enterocolitis. There are only limited data on the comparison of feeding with formula milk versus nutrient-fortified donor breast milk. This limits the applicability of the findings as nutrient fortification of breast milk is now a common practice in neonatal care. Future trials may compare growth, development and adverse outcomes in infants who receive formula milk versus nutrient-fortified donor breast milk given as a supplement to maternal expressed breast milk or as a sole diet.

Enteral intake for very low birth weight infants: what should the composition be?

Providing optimal nutrition to satisfy the growth needs of very low birth weight infants is critical. The available preterm formulas and fortified human milk diets provide protein intakes of approximately 3.5 to 3.6 g/kg/d when volumes sufficient to provide 120 kcal/kg/d are fed to these infants. These intakes support growth and protein accretion at about or slightly greater than intrauterine rate and lead to relatively increased fat deposition. However, most very low birth infants fed these diets remain below the 10th percentile of the intrauterine growth standards at discharge. There is clear evidence that, with respect to growth, very low birth infants are likely to benefit from a higher protein intake; however, there is no clear evidence that energy intakes greater than 120 kcal/kg/d are needed. Although the upper limit of protein intake and the ideal protein:energy ratio remain controversial, there is enough evidence to support the beneficial and safe use of formulas providing protein:energy ratio of 3.2 to 3.3 g/100 kcal.

Energy requirements

The determination of the appropriate energy and nutritional requirements of a newborn infant requires a clear goal of the energy and other compounds to be administered, valid methods to measure energy balance and body composition, and knowledge of the neonatal metabolic capacities. Providing an appropriate amount of energy to newborn infants remains a challenge considering the great number of newborn infants who suffer in-hospital growth retardation. The energy requirements of a newborn infant are influenced by several factors - basal metabolism, growth, energy expenditure, and energy losses - which change continuously during development. Calculating the energy requirements of preterm infants is subject to error if general recommendations are applied without recognition of the large variation in factors that influence, for example, energy expenditure. Therefore, energy recommendations should be individualized and preferably based on measurements of energy expenditure. In particular, extremely low birth-weight and very low birth-weight infants are prone to develop negative energy and nutrient balances, due to low energy intake, low energy reserves and high energy demands. Early energy accretion is not only essential for growth but also influences neurodevelopmental outcome and physical health in the long term, thereby underlining the importance of adequate neonatal nutrition.

High protein pre-term infant formula: effect on nutrient balance, metabolic status and growth

Several lines of evidence suggest that formula with protein content of 3.0 g/100 kcal does not fully meet the protein needs of very-low-birth weight infants. Our purpose was to compare nitrogen balance, metabolic status and growth in infants fed a standard (3.0 g/100 kcal; RegPro) and high (3.6 g/100 kcal; HiPro) protein infant formula. Infants were fed both formulas, each formula for one week in balanced cross-over design. Metabolic status was monitored throughout. Nutrient balance and plasma amino acids were determined at the end of each week. Data were analysed using a linear mixed model. Eighteen infants were studied. Nine infants received the RegPro and nine received HiPro formula first. Nitrogen intake, absorption and retention were greater with the HiPro formula. None of the infants developed uremia or metabolic acidosis but retinol-binding-protein and weight gain were greater with the HiPro formula. Increased protein accretion paralleled by better weight gain without evidence of metabolic stress indicates that a formula with a protein content of 3.6 g/100 kcal better meets protein needs in these rapidly-growing infants. Further studies are needed to determine whether these short-term outcomes will be translated into long-term benefits.

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.

Protein requirements in preterm infants: effect of different levels of protein intake on growth and body composition

This study compares growth and body composition in preterm infants (< or =1750 g birth weight, < or =34 wk gestation) fed three iso-caloric formulas (80 kcal/100 mL) with different protein concentrations (A = 3.3 g/100 kcal, B = 3.0 g/100 kcal, C = 2.7 g/100 kcal). The study began when full enteral feeding (150 mL/kg/d) was established and lasted until term plus 12 wk corrected age (T + 12 wca). Nutrient intake was closely monitored throughout the study; daily during initial hospital stay and following discharge averaged between each clinic visit. Anthropometry and serum biochemistries were determined weekly during initial stay and at each clinic visit. Body composition was measured after hospital discharge and at T + 12 wca. Seventy-seven infants were recruited. No differences were detected in birth/enrollment characteristics between the groups. Protein intake was closely paralleled by changes in serum urea nitrogen and differed between the groups. Infants in group A were heavier and longer and had greater head circumference at discharge, but this was confounded by a slightly older corrected age in this group. There were no significant anthropometric differences at term or T + 12 wca. No differences were detected in body composition between the groups following discharge or at T + 12 wca. An intake of 3.3 g/100 kcal appears safe and may promote increased growth before initial hospital discharge. After discharge, intakes greater than 2.7 g/100 kcal do not appear to offer clear advantage. Further studies are needed to more precisely define protein requirements in these nutritionally at-risk infants.

Energy intake, metabolic balance and growth in preterm infants fed formulas with different nonprotein energy supplements

OBJECTIVE

To study metabolic and energy balances, growth and composition of increased body mass in healthy preterm infants fed control formula or control formula with three different nonprotein energy supplements.

PATIENTS AND METHODS

Growing preterm infants (birth weight < 1,500 g and gestational age < 31 weeks) were fed standard preterm formula (control group) or the same formula enriched with three different nonprotein energy supplements. An energy supplement of 23 kcal/kg/day was achieved by adding medium-chain triglyceride and dextrinomaltose in three different caloric ratios: 33:66 in group A, 66:33 in group B, and 85:15 in group C. Energy balance was determined by open-circuit continuous (5-6 hours) measurements of energy expenditure, with simultaneous measurement of 24-hour urinary nitrogen excretion. Metabolic balance was determined by measurements of energy intake, energy oxidation, and energy output in urine and stool. The composition of body mass accretion was determined as the accretion of fat and protein in the total weight gain.

RESULTS

The fat accretion (4.9, 5.9, 6.2, and 3.8 g/kg/day in groups A, B, C and D, respectively) correlated directly with fat intake. Infants receiving standard energy intake had a fat percentage of weight gain significantly lower (28%) than that of the high-energy intake groups (31%, 40%, and 38% in groups A, B, and C, respectively). This difference corresponded to the results obtained from skinfold thickness measurements.

CONCLUSIONS

Excess nonprotein energy is stored as fat regardless of its source (fat or carbohydrate). High caloric and medium-chain triglyceride intake in otherwise healthy growing preterm infants does not promote nitrogen retention.

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.

Enhanced-calorie formulas: considerations and options

The long-term developmental impact of nutrition on the preterm newborn has recently been shown to be of even greater importance than previously recognized. Very immature or ill infants are challenged by the need for a high caloric intake, but are unable to tolerate large fluid volumes. These patients may require enhanced-calorie formulas to achieve the desired growth goals. Formula enhancement has traditionally been performed by uniquely developed recipes of base formula concentration with the addition of powdered formula or single components such as medium-chain triglycerides oil, protein, or polycose. These mixtures have been largely unstudied for bioavailability, long-term outcomes, and tolerance. Deviation from recommended protein, fat, carbohydrate, mineral, and vitamin delivery limits may impair growth or lead to undesirable side effects. The practitioner must have an understanding of when and how to use an enhanced formula and the important monitoring and assessment needs of the patient receiving enhanced-calorie formula.

Stability of respiratory quotient and growth outcomes of very low birth weight infants

Nutritional management of very low birth weight (VLBW) infants involves promoting growth at rates that mimic intrauterine rates. Nutritional intake at the recommended energy level to promote growth results in fat accretion at levels that exceed intrauterine rates for fat accretion. The respiratory quotient (RQ), the ratio of carbon dioxide produced to oxygen consumed during oxidation, provides a measure of the percentage of substrates used for energy. An RQ of greater than 0.9 indicates carbohydrate is used to meet energy needs, allowing the majority of fat intake to be stored as new tissue. The purpose of this study was to examine the stability of the RQ across time in relation to nutritional intake and growth in VLBW infants. Subjects were 9 enterally fed VLBW infants. Measurements to determine the RQ were obtained weekly for 3 weeks by indirect calorimetry. Nutritional intake and growth velocity were examined. There was no significant difference in the RQ across 3 weeks. The mean (+/- SD) RQs for each of the 3 weeks were 1.08 (+/- 0.04), 1.06 (+/- 0.05), and 1.06 (+/- 0.07), respectively. No significant differences were found across the 3 weeks for any of the macronutrient variables. Growth velocity for the period was 15.7 g/kg/day. By discharge from the NICU, 66% of the infants had weights less than the 10th percentile on an intrauterine growth reference. An RQ greater than 1.0 indicates VLBW infants are depositing excess fat. However, increased accretion rates of fat did not improve the growth outcomes of these VLBW infants.

Formula milk versus term human milk for feeding preterm or low birth weight infants

BACKGROUND

Term (mature) human breast milk, compared with artificial formula milks, may provide insufficient nutrition for growth and development in preterm or low birth weight infants. However, human milk may confer advantages to infants in terms of a decreased incidence of adverse outcomes.

OBJECTIVES

To determine if formula milk compared with term human breast milk leads to improved growth and development without significant adverse effects in low birth weight or preterm infants.

SEARCH STRATEGY

The standard search strategy of the Cochrane Neonatal Review Group was used. This included electronic searches of the Cochrane Controlled Trials Register, MEDLINE, EMBASE and previous reviews including cross references.

SELECTION CRITERIA

Randomised controlled trials comparing feeding with formula milk versus term human milk in low birth weight or preterm infants.

DATA COLLECTION AND ANALYSIS

Data were extracted using the standard methods of the Cochrane Neonatal Review Group, with separate evaluation of trial quality and data extraction by each author and synthesis of data using relative risk, risk difference and weighted mean difference.

MAIN RESULTS

Six trials, all initiated more than 20 years ago, fulfilled the pre-specified inclusion criteria. Four small trials compared feeding with standard calorie formula milk versus unfortified term human milk. Two trials compared feeding with calorie-enriched formula milk versus unfortified term human milk. No trials comparing feeding with formula milk versus nutrient-fortified term human milk were found. Only one trial reported longer term follow up of growth and development. In preterm and low birth weight infants, enteral feeding with formula milk compared with unfortified term human milk resulted in a greater rate of growth in the short term. We did not find a statistically significant difference in the incidence of necrotising enterocolitis, but this was evaluated as a pre-defined outcome in only one trial. The single trial that evaluated longer-term outcomes did not find evidence of an effect on longer-term growth and neurodevelopment.

REVIEWER'S CONCLUSIONS

In preterm and low birth weight infants, feeding with formula milk, compared with unfortified term human milk, leads to a greater rate of growth in the short term. The limited data available do not allow definite conclusions on whether adverse outcomes, including necrotising enterocolitis, are increased in infants who receive formula milk compared with term human milk. There are no data from randomised trials on the comparison of feeding with formula milk versus nutrient-fortified breast milk. This limits the implications for practice of this review as nutrient fortification of breast milk is now a common practice in neonatal care. Future trials may compare growth, development and adverse outcomes in infants who receive adapted "preterm" formula milks versus nutrient-fortified human breast milk.

Formula milk versus preterm human milk for feeding preterm or low birth weight infants

BACKGROUND

Preterm human breast milk, compared with artificial formula milk, may provide insufficient nutrition for preterm or low birth weight infants. However, human milk may confer advantages in terms of a decreased incidence of gastrointestinal and neurodevelopmental adverse outcomes.

OBJECTIVES

To determine if formula milk compared with preterm human milk leads to improved growth and development without significant adverse effects in preterm or low birth weight infants.

SEARCH STRATEGY

The standard search strategy of the Cochrane Neonatal Review Group was used. This included electronic searches of the Cochrane Controlled Trials Register, MEDLINE, EMBASE and previous reviews including cross references.

SELECTION CRITERIA

Randomised controlled trials comparing feeding with formula milk versus preterm human milk in preterm or low birth weight infants.

DATA COLLECTION AND ANALYSIS

Data were extracted using the standard methods of the Cochrane Neonatal Review Group, with separate evaluation of trial quality and data extraction by each author and synthesis of data using relative risk and mean difference.

MAIN RESULTS

Only one small trial fulfilled the pre-specified inclusion criteria (Gross 1983). In preterm and low birth weight infants, enteral feeding with protein-enriched standard calorie formula milk compared with unfortified donated preterm human milk resulted in a greater rate of short term weight gain, but not of increase in length or head circumference. In the group randomised to receive formula milk, there was an increase in the risk of feed intolerance of borderline statistical significance, but no evidence of an effect on necrotising enterocolitis. There are no data on long term growth parameters or on neurodevelopmental outcomes. There are no randomised comparisons of feeding with the preterm milk of the infant's mother versus formula milk.

REVIEWER'S CONCLUSIONS

There are very limited data from randomised trials of feeding preterm or low birth weight infants with formula milk compared with preterm human milk. This may relate to a perceived difficulty of allocating an alternative enteral feed to an infant in cases where the infant's mother wishes to feed with expressed breast milk.

Short-term growth and substrate use in very-low-birth-weight infants fed formulas with different energy contents

BACKGROUND

Currently available preterm formulas with energy contents of 3350 kJ (800 kcal)/L promote weight and length gain at rates at or above intrauterine growth rates but disproportionately increase total body fat.

OBJECTIVE

The objective of this study was to determine whether fat accretion in formula-fed, very-low-birth-weight (VLBW) infants could be decreased and net protein gain maintained by reducing energy intakes from 502 kJ (80 kcal)*kg(-)(1)*d(-)(1) [normal-energy (NE) formula] to 419 kJ (100 kcal)*kg(-)(1)*d(-)(1) [low-energy (LE) formula] while providing similar protein intakes (3.3 g*kg(-)(1)*d(-)(1)).

DESIGN

The study was a randomized, controlled trial enrolling 20 appropriate-for-gestational-age (AGA) and 16 small-for-gestational-age (SGA) VLBW infants (mean birth weight: 1.1 kg; mean gestational age: 31 wk); energy expenditure and nutrient balance were measured at 4 wk of age and anthropometric measurements were made when infants weighed 2 kg.

RESULTS

The percentage of fat in newly formed tissue was significantly lower in AGA infants fed the LE formula (n = 9) than in those fed the NE formula (n = 10) (9% compared with 23%; analysis of variance, P = 0.001). Energy expenditure was higher in AGA infants fed the NE formula than in those fed the LE formula. Skinfold thickness was markedly lower in AGA infants fed the LE formula than in those fed the NE formula, resulting in a lower estimated percentage body fat (8.0 +/- 1.9% and 10.8 +/- 3.5%, respectively; P < 0.05). Three of 6 SGA infants fed the LE formula were excluded during the study because of poor weight gain.

CONCLUSIONS

Body composition can easily be altered by changing the energy intakes of formula-fed VLBW infants. Energy intakes in these infants should be >419 kJ (100 kcal)*kg(-)(1)*d(-)(1).

[Surveillance of the very-low birthweight infant: growth and nutrition]

In very low birth weight (VLBW) infants careful growth and nutritional supervision are necessary in order to reduce the incidence of persistent growth retardation after 2 to 3 years of age. Recently, post-discharge formulas with higher protein, energy and mineral content has been developed with the aim to promote catch up growth and mineral accretion during the first months of life. Based upon the most recent nutritional and growth data, the authors propose guidelines for the nutrition and growth follow-up of VLBW infants after discharge from the neonatal unit.