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

Lyophilized (freeze-dried) human milk for preterm infants: a scoping review

Freeze-drying (FD), or lyophilization, is commonly used to preserve foods. FD offers potential to create a human milk-derived human milk fortifier, and an alternative to freeze-storing human milk. However, processing human milk is known to affect its components. This scoping review explores the effect of FD on the; macronutrient, micronutrient, vitamin, bioactive components, microbes and anti-microbial factors in human milk, and studies where lyophilized human milk has been given to newborn infants. 48 articles were identified after full text review. FD human milk reduces the fat globule size and as well as the quantity of enzymes, vitamin C and immunoglobulin. Common serum electrolyte disturbances have been reported when preterm infants' are fed FD human milk however it appears a promising method to avoid exposure of preterm infants' to cows' milk. Due to limited data, further studies exploring the safety and efficacy of FD human milk in preterm infants are needed.

Human Milk-Derived Fortifiers Compared with Bovine Milk-Derived Fortifiers in Preterm Infants: A Systematic Review and Meta-Analysis

This systematic review assessed outcomes after using human milk-derived fortifier (HMF) compared with bovine milk-derived fortifier (BMF) in preterm infants. Six randomized controlled trials (RCTs) were included. Meta-analysis using a random-effects model showed the following results: 1) lower risk of necrotizing enterocolitis (NEC; ≥Stage II) (RR: 0.38; 95% CI: 0.15, 0.95; P = 0.04, I2 = 9%; n = 334, 4 RCTs) and surgical NEC (RR: 0.13; 95% CI: 0.02, 0.67; P = 0.02, I2 = 0%; n = 209, 3 RCTs) in the HMF group; 2) no significant difference in mortality (RR: 0.40; 95% CI: 0.14, 1.15; P = 0.09, I2 = 0%; n = 334, 4 RCTs); 3) lower weight gain in the HMF group [mean difference (MD) = -1.08 g · kg-1 · d-1; 95% CI: -1.96, -0.21 g · kg-1 · d-1; P = 0.02, I2 = 0%; n = 241, 4 RCTs]; 4) no differences for length (MD = -0.11 cm/wk; 95% CI: -0.26, 0.04 cm/wk; P = 0.14, I2 = 68%) and head circumference (MD = -0.02 cm/wk; 95% CI: -0.08, 0.05 cm/wk; P = 0.59, I2 = 23%); and 5) no significant difference in late-onset sepsis (RR: 0.96; 95% CI: 0.56, 1.67; P = 0.90, I2 = 63%; n = 334, 4 RCTs). The beneficial effects of HMF for NEC were no longer significant in sensitivity analyses after excluding studies with high risk of bias. Quality of evidence as per Grading of Recommendations, Assessment, Development and Evaluation (GRADE) analysis was low to very low, and hence the confidence in these results is low. In summary, fortification of milk in preterm infants with HMF compared with BMF decreased the risk of NEC but was associated with lower weight gain. Given the low quality of evidence, adequately powered and well-designed RCTs without the influence of industry are required in this field.

The Use of Multinutrient Human Milk Fortifiers in Preterm Infants: A Systematic Review of Unanswered Questions

There is evidence that multinutrient fortification of human milk increases in-hospital growth of preterm infants, but fortification has not been shown to improve long-term growth and neurodevelopmental outcome. We aimed to ascertain whether randomized controlled trials have determined the effect of early versus late introduction of fortifiers on growth and/or other outcomes, and have compared the efficacy/adverse effects of human milk-based versus cow milk-based fortifiers. We conclude that there is little evidence that early introduction of human milk fortification affects important outcomes, and limited evidence that a bovine fortifier places the infant at a higher risk of NEC.

Considerations in meeting protein needs of the human milk-fed preterm infant

Preterm infants provided with sufficient nutrition to achieve intrauterine growth rates have the greatest potential for optimal neurodevelopment. Although human milk is the preferred feeding for preterm infants, unfortified human milk provides insufficient nutrition for the very low-birth-weight infant. Even after fortification with human milk fortifier, human milk often fails to meet the high protein needs of the smallest preterm infants, and additional protein supplementation must be provided. Although substantial evidence exists to support quantitative protein goals for human milk-fed preterm infants, the optimal type of protein for use in human milk fortification remains uncertain. This question was addressed through a PubMed literature search of prospective clinical trials conducted since 1990 in preterm or low-birth-weight infant populations. The following 3 different aspects of protein quality were evaluated: whey-to-casein ratio, hydrolyzed versus intact protein, and bovine milk protein versus human milk protein. Because of a scarcity of current studies conducted with fortified human milk, studies examining protein quality using preterm infant formulas were included to address certain components of the clinical question. Twenty-six studies were included in the review study. No definite advantage was found for any specific whey-to-casein ratio. Protein hydrolyzate products with appropriate formulations can support adequate growth and biochemical indicators of nutrition status and may reduce gastrointestinal transit time, gastroesophageal reflux events, and later incidence of atopic dermatitis in some infants. Plasma amino acid levels similar to those of infants fed exclusive human milk-based diets can be achieved with products composed of a mixture of bovine proteins, peptides, and amino acids formulated to replicate the amino acid composition of human milk. Growth and biochemical indicators of nutrition status are similar for infants fed human milk fortified with human milk protein and bovine milk protein.

The use of human milk for premature infants

Various methods have been reported and used clinically to augment the nutrient supply for human milk-fed premature infants. These methods include specialized maltinutrient powdered mixtures (fortifiers), complete liquid formulas designed to be mixed with human milk, complete powdered formulas to be mixed with human milk, and alternate feeding of human milk and preterm formula. Although the optimum nutrition of premature infants is unknown, data are accumulating to suggest that human milk, fortified with additional nutrients, is appropriate for tube-fed infants. The use of fortified human milk typically provides premature infants adequate growth, nutrient retention, and biochemical indices of nutritional status when fed at approximately 180 mL/kg/d compared with unfortified human milk. Data are needed to determine the precise quantity of nutrients to be added as supplements. Nutrient interactions have not been explored in detail. Although large quantities of calcium seem to be needed, the exogenous calcium may affect fat absorption adversely. Manipulation of milk may affect the intrinsic host-defense properties of the milk. Compared with preterm formula, the feeding of fortified human milk may provide significant protection from infection and NEC. Lastly, the potential stimulation of an enteromammary pathway through skin-to-skin contact provides species-specific antimicrobial protection for premature infants. Several of these areas require additional exploration. Thus, for premature infants, neonatal centers should encourage the feeding of fortified human milk, together with skin-to-skin contact, as reasonable methods to enhance milk production while potentially facilitating the development of an enteromammary response.

Protein metabolism in the extremely low-birth weight infant

Although extensive data are available on the impact of nutrient and protein administration on growth, plasma amino acids, and nitrogen balance in the newborn and growing infants, relatively few studies have carefully examined the dynamic aspects of protein metabolism in vivo and particularly in the micropremie or ELBW infant. These studies show that the very preterm infants, either because of immaturity or because of the intercurrent illness, have high rates of protein turnover and protein breakdown. This high rate of proteolysis is not as responsive to nutrient administration. Intervention strategies aimed at promoting nitrogen accretion, such as insulin, human growth hormone, or glutamine, have not thus far resulted in enhanced protein accretion and growth. This may be, in part, due to limitations in delivery of adequate calorie and nitrogen.

Effects of nutrients in human milk on the recipient premature infant

As the rate of survival of premature infants is increasing, more attention is necessarily focused on improving the quality of survival through optimal nutritional management. The nutritional needs of the premature infant are greater than at any other time in the life cycle. The benefits of human milk for term infants are well known. Emerging data suggest that human milk may especially benefit the premature infant. The human milk-fed premature infant may experience improved health (such as lower rates of infection and necrotizing enterocolitis), gastrointestinal function, and neurodevelopment. These factors may outweigh the concerns about adequate growth, nutrient accretion, and biochemical indices of nutritional status attributed to the lower nutrient content of human milk compared with preterm formula. Some of the nutritional concerns may be met by the use of multinutrient supplements during the time infants receive tube-feeding, generally the time prior to attaining complete oral feeding in-hospital. The available data suggest that the quality of survival of premature infants can be improved, both in the short-term and long-term, through the feeding of human milk.

Feeding strategies for premature infants: beneficial outcomes of feeding fortified human milk versus preterm formula

BACKGROUND

In a large-scale study of feeding strategies in premature infants (early vs later initiation of enteral feeding, continuous vs bolus tube-feeding, and human milk vs formula), the feeding of human milk had more effect on the outcomes measured than any other strategy studied. Therefore, this report describes the growth, nutritional status, feeding tolerance, and health of participating premature infants who were fed fortified human milk (FHM) in comparison with those who were fed exclusively preterm formula (PF).

METHODS

Premature infants were assigned randomly in a balanced two-way design to early (gastrointestinal priming for 10 days) versus late initiation of feeding (total parenteral nutrition only) and continuous infusion versus intermittent bolus tube-feeding groups. The type of milk was determined by parental choice and infants to receive their mother's milk were randomized separately from those to receive formula. The duration of the study spanned the entire hospitalization of the infant. To evaluate human milk versus formula feeding, we compared outcomes of infants fed >50 mL. kg-1. day-1 of any human milk (averaged throughout the hospitalization) with those of infants fed exclusively PF. Growth, feeding tolerance, and health status were measured daily. Serum indices of nutritional status were measured serially, and 72-hour nutrient balance studies were conducted at 6 and 9 weeks postnatally.

RESULTS

A total of 108 infants were fed either >50 mL. kg-1. day-1 human milk (FHM, n = 62) or exclusively PF (n = 46). Gestational age (28 +/- 1 weeks each), birth weight (1.07 +/- 0.17 vs 1.04 +/- 0.19 kg), birth length and head circumference, and distribution among feeding strategies were similar between groups. Infants fed FHM were discharged earlier (73 +/- 19 vs 88 +/- 47 days) despite significantly slower rates of weight gain (22 +/- 7 vs 26 +/- 6 g. kg-1. day-1), length increment (0.8 +/- 0.3 vs 1.0 +/- 0.3 cm. week-1), and increment in the sum of five skinfold measurements (0.86 +/- 0.40 vs 1.23 +/- 0.42 mm. week-1) than infants fed PF. The incidence of necrotizing enterocolitis and late-onset sepsis was less in the FHM group. Overall, there were no differences in any measure of feeding tolerance between groups. Milk intakes of infants fed FHM were significantly greater than those fed PF (180 +/- 13 vs 157 +/- 10 mL. kg-1. day-1). The intakes of nitrogen and copper were higher and magnesium and zinc were lower in group FHM versus PF. Fat and energy absorption were lower and phosphorus, zinc, and copper absorption were higher in group FHM versus PF. The postnatal retention (balance) surpassed the intrauterine accretion rate of nitrogen, phosphorus, magnesium, zinc, and copper in the FHM group, and of nitrogen, magnesium, and copper in the PF group.

CONCLUSIONS

Although the study does not allow a comparison of FHM with unfortified human milk, the data suggest that the unique properties of human milk promote an improved host defense and gastrointestinal function compared with the feeding of formula. The benefits of improved health (less sepsis and necrotizing enterocolitis) associated with the feeding of FHM outweighed the slower rate of growth observed, suggesting that the feeding of FHM should be promoted actively in premature infants.

Metabolic and energy balance in small- and appropriate-for-gestational-age, very low-birth-weight infants

This study compared nutrient utilization and postnatal weight gain composition in eight appropriate for gestational age (AGA: birth weight 1293 +/- 107 g; gestational age 28.8 +/- 1.4 weeks) and eight symmetrically growth-retarded (SGA: birth weight 1110 +/- 230 g; gestational age 32.7 +/- 1.9 weeks), very low-birth-weight (VLBW) infants. There was no significant difference in protein, mineral and energy intake between AGA and SGA infants. Nitrogen absorption (84 +/- 3 and 83 +/- 4%) and nitrogen retention (356 +/- 48 and 352 +/- 43 mg/kg/day) were similar in both groups. Fat absorption tended to be lower in AGA (78 +/- 15%) than in SGA (87 +/- 4%) infants. Calcium, phosphorus and magnesium absorptions were similar in AGA and SGA infants. Metabolizable energy utilization was similar in both groups; about 55% was expended and 45% stored in new tissues. Energy expenditure was 58 +/- 4 kcal/kg/day in SGA infants and 61 +/- 9 kcal/kg/day in AGA infants. Weight gain and its composition were similar in both groups. We conclude that nutrient and energy utilization are similar in AGA and symmetrically growth-retarded, VLBW infants.