Effect of carbohydrates on calcium absorption in premature infants

Enteral Nutrition in Preterm Infants (2022): A Position Paper From the ESPGHAN Committee on Nutrition and Invited Experts

OBJECTIVES

To review the current literature and develop consensus conclusions and recommendations on nutrient intakes and nutritional practice in preterm infants with birthweight <1800 g.

METHODS

The European Society of Pediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) Committee of Nutrition (CoN) led a process that included CoN members and invited experts. Invited experts with specific expertise were chosen to represent as broad a geographical spread as possible. A list of topics was developed, and individual leads were assigned to topics along with other members, who reviewed the current literature. A single face-to-face meeting was held in February 2020. Provisional conclusions and recommendations were developed between 2020 and 2021, and these were voted on electronically by all members of the working group between 2021 and 2022. Where >90% consensus was not achieved, online discussion meetings were held, along with further voting until agreement was reached.

RESULTS

In general, there is a lack of strong evidence for most nutrients and topics. The summary paper is supported by additional supplementary digital content that provide a fuller explanation of the literature and relevant physiology: introduction and overview; human milk reference data; intakes of water, protein, energy, lipid, carbohydrate, electrolytes, minerals, trace elements, water soluble vitamins, and fat soluble vitamins; feeding mode including mineral enteral feeding, feed advancement, management of gastric residuals, gastric tube placement and bolus or continuous feeding; growth; breastmilk buccal colostrum, donor human milk, and risks of cytomegalovirus infection; hydrolyzed protein and osmolality; supplemental bionutrients; and use of breastmilk fortifier.

CONCLUSIONS

We provide updated ESPGHAN CoN consensus-based conclusions and recommendations on nutrient intakes and nutritional management for preterm infants.

Calcium nutrition and metabolism during infancy

Calcium is a vital mineral for the developing newborn infant. This review discusses perinatal and neonatal calcium metabolism, with an emphasis on enteral calcium absorption and the nutritional factors affecting calcium bioavailability including the three major endocrine hormones involved in calcium metabolism: parathyroid hormone, vitamin D, and calcitonin. The placenta transports calcium to the fetus throughout pregnancy, with the largest amount of fetal calcium accumulation occurring in the third trimester. At birth, the newborn transitions to intestinal absorption to meet the body's calcium needs. Most calcium is absorbed by paracellular passive diffusion in the small intestine. Calcium intestinal absorption is affected by the type and amount of calcium ingested. It is also affected by the amount of intestinal calcium that is bound to dietary fats and proteins. One major consequence of decreased calcium absorption is metabolic bone disease in which there is a failure of complete mineralization of the bone osteoid.

Influence of changes in lactase activity and small-intestinal mucosal growth on lactose digestion and absorption in preterm infants

BACKGROUND

Feeding intolerance (ie, achieving and maintaining full enteral feedings) is a significant problem in preterm infants. A relation exists between feeding intolerance and incomplete lactose digestion.

OBJECTIVES

We sought to identify the factors relating to lactose digestion and absorption, lactase activity, and small-intestinal mucosal growth.

DESIGN

Lactose digestion and absorption, lactase-specific activity, and lumen-to-mucosa water flux as a measure of small-intestinal mucosal surface area were determined by using the triple-lumen perfusion technique on 2 occasions 3 wk apart in 10 preterm infants (x+/-SEM gestational age: 28.0+/-0.2 wk).

RESULTS

Lactose digestion and absorption and lactase activity doubled between studies (P=0.035 and P=0.041, respectively). The change in digestion and absorption was related to lactase activity (P=0.034, R2=0.38). Lactase activity correlated with gestational age at birth (P=0.012, R2=0.51). The number of days of feeding explained 80% of the variability in small-intestinal mucosal surface area (P=0.001).

CONCLUSIONS

To our knowledge, this is the first study to measure directly lactose digestion and absorption, lactase activity, and small-intestinal surface area in preterm infants. Changes in lactose absorption relate primarily to lactase activity rather than to mucosal growth. We showed directly a relation between enteral feeding and small-intestinal mucosal growth.

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.

Divalent metals inhibit and lactose stimulates zinc transport across brush border membrane vesicles from piglets

Interactions between metals of similar coordination chemistry are of relevance to infant nutrition due to the highly variable metal:metal ratios found in formulas. Using ratios similar to those found in infant formulas, our objectives were to determine the effects of metals and of lactose and other saccharides on Zn(+2) transport across intestinal brush border membranes. Brush border membrane vesicles prepared from intestines of 5 preweaned piglets were used to determine whether Ca(+2), Mg(+2), Fe(+2), Cu(+2), Cd(+2), or Mn(+2) would antagonize Zn(+2) uptake. (65)Zn(+2) uptake by brush border membrane vesicles was measured over 20 min with metal concentrations constant, and at 1 min with increasing metal concentrations. Zn(+2) bound to the external surface of vesicles was removed with ethylenediamine-tetraacetic acid. Lactose induced Zn(+2) uptake to a greater extent than glucose polymer, whereas maltose, galactose, or galactose/glucose had no effect. Over 20 min, a 10:1 concentration of Fe(+2), Cd(+2), Cu(+2), and Mn(+2) lowered Zn(+2) uptake significantly (P < 0.05). Higher concentrations of divalent cation significantly lowered Zn(+2) (0.2 or 0.1 mM) uptake for all metals tested (P < 0.05), except for Mn(+2) (0.1 mM Zn(+2)). Inhibition constant determination quantified relative competitive potential with Mg(+2) < Ca(+2) << Mn(+2) < Fe(+2) < Zn(+2) << Cu(+2). Relative amounts of Ca(+2), Mg(+2), and Fe(+2) similar to those found in infant formulas reduced Zn(+2) uptake by at least 40%. Our data demonstrate that dietary minerals compete during brush border membrane transport, and may help explain antagonistic mineral interactions observed in vivo. Divalent metal concentrations and lactose content of milk affect zinc absorption in neonates and must be carefully considered in formula design.

Transgalactooligosaccharides stimulate calcium absorption in postmenopausal women

The aim of this study was to investigate whether a product rich in transgalactooligosaccharides (TOS, Elix'or) stimulates true Ca absorption in postmenopausal women. The study was a double-blind, randomized crossover study, consisting of two 9-d treatment periods separated by a 19-d washout period. During the treatment periods, 12 subjects drank 200 mL yogurt drink twice (at breakfast and lunch) containing either TOS (20 g/d) or the reference substance, sucrose. On d 8 of each treatment period, (44)Ca and (48)Ca were administered orally and intravenously, respectively. Before and during the 36 h after isotope administration, urine was collected and the ratios of isotopes present were measured by inductively coupled plasma mass spectrometry (ICP-MS). From the isotope enrichments, true calcium absorption was calculated. TOS increased true calcium absorption 16%, from (mean +/- SD) 20.6 +/- 7.0% during the reference treatment to 23.9 +/- 6.9% during the TOS treatment (P: = 0.04, one-sided). In conclusion, in this study in postmenopausal women, greater Ca absorption was observed after consumption of a product rich in TOS (Elix'or) compared with the reference treatment. This increase in Ca absorption was likely due solely to TOS. The increased Ca absorption was not accompanied by increased urinary Ca excretion, meaning that TOS also may indirectly increase the uptake of Ca by bones and/or inhibit bone resorption.

Infant feeding: a critical look at infant formulas

Commercially available infant formulas serve as the best alternative to human milk when breastfeeding is not possible. Infant formulas are designed specifically to mimic the composition of human milk or the functional aspects of human milk feeding. This review highlights the issues related to the composition of infant formulas. The most hotly debated issue currently is whether to add long-chain polyunsaturated fatty acids to infant formulas. Other controversial topics include the safety and efficacy of soy-based protein formulas, protein quantity and quality as they relate to the infant's nutritional needs and feeding tolerance, and the replacement of lactose with other carbohydrate sources for specialized infant formulas. Recent modifications in the fat blend of infant formulas have led to improved fat digestibility. However, the full spectrum of benefits associated with the addition of nucleotides awaits further study. Modifications to infant formulas are made when the preponderance of scientific evidence suggests that the compositional change will better meet the nutritional needs of the infant.

Can the elimination of lactose from formula improve feeding tolerance in premature infants?

OBJECTIVE

To determine whether a low-lactose formula (LLF, <5% lactose) would ameliorate feeding intolerance in premature infants.

STUDY DESIGN

Prospective, randomized, controlled trial involving 306 infants <36 weeks' gestation and weighing <1800 g who received either lactose-containing formula (LCF) 24 kcal/oz or a specially prepared LLF, which was comparable to the LCF except for the functional replacement of lactose with maltose. We examined outcome variables of feeding intolerance and cases of necrotizing enterocolitis (NEC) and suspected NEC.

RESULTS

One hundred forty-nine infants were assigned to receive LCF, of which 99 infants received LCF only. One hundred fifty infants were assigned to receive LLF, of which 102 infants received LLF only. The remaining infants received LCF or LLF plus some quantity of human milk or human milk alone. Infants receiving LLF had improved enteral caloric intake and weight gain, reached full feeds faster, had less gastric residual, spent less time without oral intake, and had fewer feedings stopped than the LCF group. The number of cases of NEC and suspected NEC was similar in both groups.

CONCLUSION

Low-lactose premature infant formula improved feeding tolerance. There was no evidence that LLF altered the incidence of NEC, but the incidence of NEC in this study was too low to draw conclusions.

Early feeding, feeding tolerance, and lactase activity in preterm infants

OBJECTIVE

We sought to ascertain whether the timing of feeding initiation affected the development of intestinal lactase activity and whether there are clinical ramifications of lower lactase activity.

STUDY DESIGN

Preterm infants (26 to 30 weeks' gestation; n = 135) were randomly assigned to begin enteral feedings at either 4 (early group) or 15 days of age (standard group). At 10, 28, and 50 days of age lactase activity was determined by measuring the urinary ratio of lactulose/lactose after the 2 sugars were administered.

RESULTS

Lactase activity increased significantly over time. Infants in the early group had greater lactase activity at 10 days of age (by 100%) and 28 days of age (by 60%) than the standard group. At 10 days of age lactase activity was greater in milk- versus formula-fed infants. The time required to achieve full enteral feedings, the number of abnormal abdominal x-ray examinations, and the total number of abdominal x-ray examinations were inversely related to lactase activity.

CONCLUSIONS

Early feeding increases intestinal lactase activity in preterm infants. Lactase activity is a marker of intestinal maturity and may influence clinical outcomes. Whether the effects of milk on lactase activity were due to the greater concentration of lactose in human milk compared with that in formula must be determined.

Randomised controlled trial of a synthetic triglyceride milk formula for preterm infants

AIMS

To test whether use of infant formula containing synthetic structured triglycerides results in: (i) increased palmitate absorption; (ii) increased total fat absorption; (iii) reduction in calcium soap formation in the gut; and hence (iv) increased calcium absorption.

METHODS

A randomised study was made of 24 infants comparing three formulas, one containing the synthetic fat Betapol with 74% of palmitate in the 2-position, which was substantially higher than in the two comparison diets (8.4% and 28%). The hypothesised outcomes were tested using balance studies, detailed chemical analysis of stool specimens and dual calcium isotope tracers (44calcium orally and 46calcium intravenously).

RESULTS

Three of the four hypotheses were confirmed: use of a formula rich in 2-position palmitate (i) improved palmitate (16:0) and also (18:0) absorption; (ii) reduced the formation of insoluble calcium soaps in the stool; and (iii) improved calcium absorption, determined by the dual tracer technique from 42 (SE 3)% to 57 (7)%.

CONCLUSION

Synthetic triglycerides that mimic the stereoisometric structure of those in breast milk may have a valuable role in the design of formulas used for preterm infants in neonatal intensive care units.