High-protein formulas: evidence for use in preterm infants

High protein intake on later outcomes in preterm children: a systematic review and meta-analysis

BACKGROUND

Appropriate protein intake is crucial for growth and development in children born preterm. We assessed the effects of high (HP) versus low protein (LP) intake on neurodevelopment, growth, and biochemical anomalies in these children.

METHODS

Randomised and quasi-randomised trials providing protein to children born preterm (<37 completed weeks of gestation) were searched following PRISMA guideline in three databases and four registers (PROSPERO registration CRD42022325659). Random-effects model was used for assessing the effects of HP (≥3.5 g/kg/d) vs. LP (<3.5 g/kg/d).

RESULTS

Data from forty-four studies (n = 5338) showed HP might slightly reduce the chance of survival without neurodisability at ≥12 months (four studies, 1109 children, relative risk [RR] 0.95 [95% CI 0.90, 1.01]; P = 0.13; low certainty evidence) and might increase risk of cognitive impairment at toddler age (two studies; 436 children; RR 1.36 [0.89, 2.09]; P = 0.16; low certainty evidence). At discharge or 36 weeks, HP intake might result in higher weight and greater head circumference z-scores. HP intake probably increased the risk of hypophosphatemia, hypercalcemia, refeeding syndrome and high blood urea, but reduced risk of hyperglycaemia.

CONCLUSIONS

HP intake for children born preterm may be harmful for neonatal metabolism and later neurodisability and has few short-term benefits for growth.

IMPACT STATEMENT

Planned high protein intake after birth for infants born preterm might be harmful for survival, neurodisability and metabolism during infancy and did not improve growth after the neonatal period. Protein intake ≥3.5 g/kg/d should not be recommended for children born preterm.

Acidified Feedings in Preterm Infants: A Historical and Physiological Perspective

The use of acidified milk for feeding infants has a long, interesting history that appears to have developed from the use of buttermilk in Holland as early as the late 19th century for feeding infants with diarrhea. Physicians in the early 20th century assumed that the observed benefits were from buttermilk's acidity leading to the practice of acidifying infant formula. The historical and physiological perspective on the use of acidified infant formula is now especially relevant with the emergence of an acidified liquid human milk fortifier for preterm infants. Here, we review that history, with a deeper dive into the contemporary research on the use of acidified human milk fortifiers, the consequences for preterm infants, and the underlying physiological mechanisms. KEY POINTS: · In the late 19th and early 20th century acidified feedings were in common use for sick infants.. · By the mid-20th century, acidified feedings tested in preterm infants resulted in acidic physiology and poor growth.. · The current practice of acidifying feedings in preterm infants has been associated with metabolic acidosis, poor tolerance, and delayed growth..

Carbohydrate supplementation of human milk to promote growth in preterm infants

BACKGROUND

Preterm infants are born with low glycogen stores and require higher glucose intake to match fetal accretion rates. In spite of the myriad benefits of breast milk for preterm infants, it may not adequately meet the needs of these rapidly growing infants. Supplementing human milk with carbohydrates may help. However, there is a paucity of data on assessment of benefits or harms of carbohydrate supplementation of human milk to promote growth in preterm infants. This is a 2020 update of a Cochrane Review first published in 1999.

OBJECTIVES

To determine whether human milk supplemented with carbohydrate compared with unsupplemented human milk fed to preterm infants improves growth, body composition, and cardio-metabolic and neurodevelopmental outcomes without significant adverse effects.

SEARCH METHODS

We used the standard search strategy of Cochrane Neonatal to search Cochrane Central Register of Controlled Trials (CENTRAL 2019, Issue 8) in the Cochrane Library and MEDLINE via PubMed on 22 August 2019. We also searched clinical trials databases and the reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials.

SELECTION CRITERIA

Published and unpublished controlled trials were eligible if they used random or quasi-random methods to allocate preterm infants in hospital fed human milk to supplementation or no supplementation with additional carbohydrate.

DATA COLLECTION AND ANALYSIS

Two review authors independently abstracted data and assessed trial quality and the quality of evidence at the outcome level using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) method. We planned to perform meta-analyses using risk ratios (RRs) for dichotomous data and mean differences (MDs) for continuous data, with their respective 95% confidence intervals (CIs). We planned to use a fixed-effect model and to explore potential causes of heterogeneity via sensitivity analyses. We contacted study authors for additional information.

MAIN RESULTS

One unblinded, quasi-randomised controlled trial (RCT) assessing effects of carbohydrate supplementation of human milk in the form of a prebiotic in 75 preterm infants was eligible for inclusion in this review. We identified two publications of the same trial, which reported different methods regarding blinding and randomisation. Study authors confirmed that these publications pertain to the same trial, but they have not yet clarified which method is correct. We were unable to reproduce analyses from the data presented. At 30 days of age, the mean weight of preterm infants in the trial was greater in the prebiotic carbohydrate-supplemented group than in the unsupplemented group (MD 160.4 grams, 95% CI 12.4 to 308.4 grams; one RCT, N = 75; very low-quality evidence). We found no evidence of a clear difference in risk of feeding intolerance (RR 0.64, 95% CI 0.36 to 1.15; one RCT, N = 75 infants; very low-quality evidence) or necrotising enterocolitis (NEC) (RR 0.2, 95% CI 0.02 to 1.3; one RCT, N = 75 infants; very low-quality evidence) between the prebiotic-supplemented group and the unsupplemented group. Duration of hospital stay was shorter in the prebiotic group than in the control group at a median (range) of 16 (9 to 45) days (95% CI 15.34 to 24.09) and 25 (11 to 80) days (95% CI 25.52 to 34.39), respectively. No other data were available for assessing effects of carbohydrate supplementation on short- and long-term growth, body mass index, body composition, and neurodevelopmental or cardio-metabolic outcomes.

AUTHORS' CONCLUSIONS

We found insufficient evidence on the short- and long-term effects of carbohydrate supplementation of human milk in preterm infants. The only trial included in this review presented very low-quality evidence, and study authors provided uncertain information about study methods and analysis. The evidence may be limited in its applicability because researchers included a small sample of preterm infants from a single centre. However, the outcomes assessed are common to all preterm infants, and this trial demonstrates the feasibility of prebiotic carbohydrate supplementation in upper-middle-income countries. Future trials should assess the safety and efficacy of different types and concentrations of carbohydrate supplementation for preterm infants fed human milk. Although prebiotic carbohydrate supplementation in preterm infants is currently a topic of active research, we do not envisage that further trials of digestible carbohydrates will be conducted, as this is currently done as a component of multi-nutrient human milk fortification. Hence we do not plan to publish any further updates of this review.

Carbohydrate supplementation of human milk to promote growth in preterm infants

BACKGROUND

Preterm infants are born with low glycogen stores and require higher glucose intake to match fetal accretion rates. In spite of the myriad benefits of breast milk for preterm infants, it may not adequately meet the needs of these rapidly growing infants. Supplementing human milk with carbohydrates may help. However, there is a paucity of data on assessment of benefits or harms of carbohydrate supplementation of human milk to promote growth in preterm infants. This is a 2018 update of a Cochrane Review first published in 1999.

OBJECTIVES

To determine whether human milk supplemented with carbohydrate compared with unsupplemented human milk fed to preterm infants improves growth, body composition, and cardio-metabolic and neurodevelopmental outcomes without significant adverse effects.

SEARCH METHODS

We used the standard search strategy of the Cochrane Neonatal Review Group to search the Cochrane Central Register of Controlled Trials (CENTRAL; 2017, Issue 8), MEDLINE via PubMed (1966 to 21 February 2018), Embase (1980 to 21 February 2018), and the Cumulative Index to Nursing and Allied Health Literature (CINAHL; 1982 to 21 February 2018). We also searched clinical trials databases, conference proceedings, and reference lists of retrieved articles for randomised controlled trials (RCTs) and quasi-randomised trials.

SELECTION CRITERIA

Published and unpublished controlled trials were eligible if they used random or quasi-random methods to allocate preterm infants in hospital fed human milk to supplementation or no supplementation with additional carbohydrate.

DATA COLLECTION AND ANALYSIS

Two review authors independently abstracted data and assessed trial quality and the quality of evidence at the outcome level using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) method. We planned to perform meta-analyses using risk ratios (RRs) for dichotomous data and mean differences (MDs) for continuous data, with their respective 95% confidence intervals (CIs). We planned to use a fixed-effect model and to explore potential causes of heterogeneity via sensitivity analyses. We contacted study authors for additional information.

MAIN RESULTS

One unblinded, quasi-randomised controlled trial (RCT) assessing effects of carbohydrate supplementation of human milk in the form of a prebiotic in 75 preterm infants was eligible for inclusion in this review. We identified two publications of the same trial, which reported different methods regarding blinding and randomisation. Study authors confirmed that these publications pertain to the same trial, but they have not yet clarified which method is correct. We were unable to reproduce analyses from the data presented. At 30 days of age, the mean weight of preterm infants in the trial was greater in the prebiotic carbohydrate-supplemented group than in the unsupplemented group (MD 160.4 grams, 95% CI 12.4 to 308.4 grams; one RCT, N = 75; very low-quality evidence). We found no evidence of a clear difference in risk of feeding intolerance (RR 0.64, 95% CI 0.36 to 1.15; one RCT, N = 75 infants; very low-quality evidence) or necrotising enterocolitis (NEC) (RR 0.2, 95% CI 0.02 to 1.3; one RCT, N = 75 infants; very low-quality evidence) between the prebiotic-supplemented group and the unsupplemented group. Duration of hospital stay was shorter in the prebiotic group than in the control group at a median (range) of 16 (9 to 45) days (95% CI 15.34 to 24.09) and 25 (11 to 80) days (95% CI 25.52 to 34.39), respectively. No other data were available for assessing effects of carbohydrate supplementation on short- and long-term growth, body mass index, body composition, and neurodevelopmental or cardio-metabolic outcomes.

AUTHORS' CONCLUSIONS

We found insufficient evidence on the short- and long-term effects of carbohydrate supplementation of human milk in preterm infants. The only trial included in this review presented very low-quality evidence, and study authors provided uncertain information about study methods and analysis. The evidence may be limited in its applicability because researchers included a small sample of preterm infants from a single centre. However, the outcomes assessed are common to all preterm infants, and this trial demonstrates the feasibility of prebiotic carbohydrate supplementation in upper-middle-income countries. Future trials should assess the safety and efficacy of different types and concentrations of carbohydrate supplementation for preterm infants fed human milk. Although prebiotic carbohydrate supplementation in preterm infants is currently a topic of active research, we do not envisage that further trials of digestible carbohydrates will be conducted, as this is currently done as a component of multi-nutrient human milk fortification. Hence we do not plan to publish any further updates of this review.

Preterm formula use in the preterm very low birth weight infant

Whereas human milk is the recommended diet for all infants, preterm formulas are indicated for enteral feeding of preterm very low birth weight infants when sufficient maternal breast milk and donor human milk are not available. Feeding with preterm formulas helps to ensure consistent delivery of nutrients. The balance of risks and benefits of feeding preterm formulas versus supplemented maternal and donor breast milk for preterm infants, however, is uncertain. Numerous studies and extensive practice have shown improved growth with preterm formulas, but there is concern for increased risks of necrotizing enterocolitis, possibly from cow milk antigen in the formulas or from different gut microbiomes, increased duration of total parenteral nutrition, and increased rates of sepsis in infants receiving preterm formulas. Furthermore, whereas preterm formulas improve neurodevelopmental outcomes compared to term formulas and unfortified donor milk, they do not produce neurodevelopmental outcomes better than fortified human milk, again indicating that maternal milk has unique properties that formulas need to mimic as closely as possible.

Early gradual feeding with bovine colostrum improves gut function and NEC resistance relative to infant formula in preterm pigs

It is unclear when and how to start enteral feeding for preterm infants when mother's milk is not available. We hypothesized that early and slow advancement with either formula or bovine colostrum stimulates gut maturation and prevents necrotizing enterocolitis (NEC) in preterm pigs, used as models for preterm infants. Pigs were given either total parenteral nutrition (TPN, n = 14) or slowly advancing volumes (16-64 ml·kg(-1)·day(-1)) of preterm infant formula (IF, n = 15) or bovine colostrum (BC, n = 13), both given as adjunct to parenteral nutrition. On day 5, both enteral diets increased intestinal mass (27 ± 1 vs. 22 ± 1 g/kg) and glucagon-like peptide 2 release, relative to TPN (P < 0.05). The incidence of mild NEC lesions was higher in IF than BC and TPN pigs (60 vs. 0 and 15%, respectively, P < 0.05). Only the IF pigs showed reduced gastric emptying and gastric inhibitory polypeptide release, and increased tissue proinflammatory cytokine levels (IL-1β and IL-8, P < 0.05) and expression of immune-related genes (AOAH, LBP, CXCL10, TLR2), relative to TPN. The IF pigs also showed reduced intestinal villus-to-crypt ratio, lactose digestion, and some plasma amino acids (Arg, Cit, Gln, Tyr, Val), and higher intestinal permeability, compared with BC pigs (all P < 0.05). Colonic microbiota analyses showed limited differences among groups. Early feeding with formula induces intestinal dysfunction whereas bovine colostrum supports gut maturation when mother's milk is absent during the first week after preterm birth. A diet-dependent feeding guideline may be required for newborn preterm infants.

Expressing breast milk at home for 24-h periods provides viable samples for macronutrient analysis

AIM

This study aimed to evaluate the reproducibility of macronutrient measurements of domestic pooled human milk from mothers with preterm infants and to see how the results affected human milk fortifications.

METHODS

We asked 28 new mothers to express their breast milk for 24 h on two consecutive days and repeat the process at weekly intervals. The samples were analysed using mid-infrared technology to calculate the differences between the milk collected on two consecutive days for reproducibility and the total protein supply with standard fortification.

RESULTS

There was a significant linear correlation between the two consecutive days with regard to protein (r = 0.94, p < 0.001), lipids (r = 0.86, p < 0.001), lactose (r = 0.91, p < 0.001) and 24-h volume (r = 0.96, p < 0.001). The percentage of the samples that would provide a protein supply of 3.5-4.5 g/kg/d with a fortification of 0.6 and 1.2 g protein/100 mL at a volume of 170 mL/kg were 28% and 41%, respectively.

CONCLUSION

The domestic pooling of 24-h expressed human milk for macronutrient analysis was a simple and reliable way of obtaining representative data. Standard fortification implies there is a risk of under- and over-nutrition, and individual fortification may improve the nutrition of preterm infants.

Bolus vs. continuous feeding to optimize anabolism in neonates

PURPOSE OF REVIEW

Neonates with feeding difficulties can be fed by orogastric tube, using either continuous or bolus delivery. This review reports on recent findings that bolus is advantageous compared to continuous feeding in supporting optimal protein anabolism.

RECENT FINDINGS

Whether bolus or continuous feeding is more beneficial has been controversial, largely due to limitations inherent in clinical studies, such as the presence of confounding variables and the inability to use invasive approaches. Recent studies using the piglet as a model of the human neonate showed that, compared to continuous feeding, bolus feeding enhances protein synthesis and promotes greater protein deposition. The increase in protein synthesis occurs in muscles of varying fiber type and in visceral tissues whereas muscle protein degradation is largely insensitive to feeding pattern. This higher protein synthesis rate is enabled by the rapid and profound increases in circulating amino acids and insulin that occur following a bolus feed, which activate the intracellular signaling pathways leading to mRNA translation.

SUMMARY

Recent findings indicate that bolus feeding enhances protein synthesis more than continuous feeding and promotes greater protein anabolism. The difference in response is attributable to the pulsatile pattern of amino acid-induced and insulin-induced translation initiation induced only by bolus feeding.