Protein in Neonatal and Infant Nutrition: Recent Updates

86th Nestlé Nutrition Institute Workshop, Beijing, May 2015

J. Bhatia, R. Shamir, Y. Vandenplas

• Publisher: S. Karger
• Year: 2016
• ISBN:
  9783318054835
• Topic: Medicine
• Subtopic: Nutrition, Dietics & Bariatrics

Protein plays a vital role in growth and development and is able to 'program' healthy growth by influencing gene methylation for positive long-term health outcomes. The understanding of these mechanisms is critical to support and improve the health of future generations in both the short and long term.The first part of this book reviews the role of hydrolyzed proteins in infant feeding and the evidence-based benefits of their use in non-breastfed infants at risk of allergy and in infants with functional gastrointestinal disorders. The second part focuses on human milk and its potential alternatives in the feeding of healthy term infants. The final section is dedicated to preterm infants, their nutrition needs, and physiological capacities to ingest adequate amounts of protein for appropriate growth and development. Presenting the latest scientific findings on protein in early nutrition, this publication provides essential reading for pediatricians and researchers alike.

Hydrolyzed Protein in Infant Feeding

Bhatia J, Shamir R, Vandenplas Y (eds): Protein in Neonatal and Infant Nutrition: Recent Updates.
Nestlé Nutr Inst Workshop Ser, vol 86, pp 1-10, (DOI: 10.1159/000442697)
Nestec Ltd., Vevey/S. Karger AG., Basel, © 2016

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Proteins, Peptides and Amino Acids: Role in Infant Nutrition

Sophie Nutten

Nutrition and Health Research Department, Nestlé Research Center, Lausanne, Switzerland

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Abstract

Proteins are polymers composed of 30 or more amino acids; some of them are essential dietary components, since they are not synthetized by human metabolic processes. They are crucial for healthy growth and development and influence major functions of the body. The infant’s first year is a critical time of rapid growth and development, which must be supported by a high rate of protein synthesis. Breast milk, as a single specific food source in the first months of life, is providing the total protein and essential amino acids required. Infant formulas have been designed for infants who cannot be breastfed. They should be similar to breast milk in their composition and their functional outcomes, insuring appropriate growth, optimal development, maturation of the immune system, easy digestion and healthy metabolic programming. By modifying their protein components, specific infant formulas have also been developed for specific needs. For example, partially hydrolyzed (prevention of atopic dermatitis) and extensively hydrolyzed or amino-acid-based infant formulas (reduction in allergy symptoms) have been designed for the management of cow’s milk protein allergy. In conclusion, proteins provided via breast milk or infant formula are essential components of the infant’s diet; therefore, the specific quality, quantity and conformation of proteins are of utmost importance for healthy growth and development.

© 2016 Nestec Ltd., Vevey/S. Karger AG, Basel

Proteins, Peptides and Amino Acids: Definitions

Proteins, from the Greek proetios (meaning ‘first’), are a fundamental component for life. They are the second most abundant chemical compound in the body after water. Following digestion, dietary proteins are absorbed as amino acids, which then contribute to the total amino acid pool, from which the body’s proteins are synthetized. Proteins are the main building blocks of the body and are involved in maintaining numerous body functions, in repairing or replacing cells or tissues, and in growth.

Table 1. Essential and nonessential amino acids

Nonessential amino acids (can be synthetized by the human body)	Conditionally essential amino acids (can be synthetized by the human body except in certain conditions)	Essential amino acids (cannot be synthetized by the human body; must be supplied through nutrition)
Alanine	Arginine	Histidine
Aspartate	Asparagine	Isoleucine
Glutamate	Cysteine^1	Leucine
	Glutamine	Lysine
	Glycine	Methionine
	Proline	Phenylalanine
	Serine	Threonine
	Tyrosine^1	Tryptophan
		Valine
^1 Requires essential amino acid precursors (methionine and phenylalanine).

They are polymers, built from 20 different amino acids. The distinction between proteins and peptides is their size. Peptides are chains of 2-30 amino acids and proteins are peptides that consist of more than 30 amino acids. The various properties of peptides and proteins depend not only on their component amino acids and their sequence in peptide chains, but also on the way the peptide chains are stretched, coiled or folded in space in secondary structures. Proteins and large peptides adopt a geometric shape, which is referred to as tertiary structure, and finally many proteins are actually assemblies of several polypeptides, which are known as protein subunits.

Unlike other macronutrients such as fat or carbohydrates, the body does not have major protein stores. Therefore, proteins must be supplied from dietary sources. Some amino acids are essential dietary components, since they are not synthetized by human metabolic processes. All 20 amino acids are important for protein synthesis, but some can be synthetized from other metabolic precursors: they are called the nonessential amino acids. Others cannot be synthetized by the human body and then have to be supplied through nutrition: they are the essential amino acids. A third category consists of the conditionally essential amino acids; they can be synthetized by the human body except in certain conditions (e.g. trauma, stress, sepsis or surgery) when the physiological demands may result in the need for these nonessential amino acids to be greater than the body’s ability to produce them (table 1).

Fig. 1. Proteins influence all aspects of growth and development.

Proteins are nutrients essential to life. They are present in and vital to every living cell. They are essential for healthy growth and development, and also influence major functions of the body (fig. 1). In the form of skin, hair, callus, cartilage, muscles, tendons and ligaments, proteins hold together, protect and provide structure to the body. In the form of enzymes, hormones, antibodies and globulins, they catalyze, regulate and ensure proper functioning of the body. In the form of hemoglobin, myoglobin and various lipoproteins, they transport oxygen and other substances in the organism.

Protein Needs in Infancy

Current research is dedicated to understand the role and importance of nutrition in early postnatal life on health in later life. Optimal patterns of infant feeding are important first to support healthy growth and development in infancy but also as determinants of health in later life. It is known that inadequate nutrition and retardation of growth in infancy can result in permanent stunting as well as potentially long-lasting deficits in neurological function or metabolic health for example [1, 2].

The infant’s first year of life is a critical time of rapid growth and development. Growth and development between birth and weaning are crucial for long-term well-being. The rapid growth of the baby (the body weight of a baby doubles by 6 months) must be supported by a high rate of protein synthesis. The rate of protein synthesis and turnover are then exceptionally high in infants relative to their body weight. In the first month of life, they need around 3.5 times as much protein per kilogram of body weight as an adult. Although growth velocity, and thereby protein requirements, rapidly declines during the first 3 months of life, at the age of 4-6 months, infants still need more than 60%, and at 6-12 years around 40% more protein than adults per kilogram of body weight.

Requirements for proteins are expressed in terms of total proteins and individual amino acids, meaning that both the quantity and the quality of proteins supplied are important.

Breast Milk

The infant’s nutritional requirements in early life are primarily satisfied by a single and highly specific food source: breast milk. Human milk is recommended as the optimal nutrient source for infants and is associated with several short- and long-term benefits for child health. Health benefits of breast milk are multiple, but a reduced risk of infectious diarrhea and acute otitis media are the best documented [3], and evidence from developing countries demonstrates that under conditions of poor hygiene breastfeeding can be a matter of life or death [4]. It has also been suggested that breastfeeding is associated with a reduced risk of cardiovascular events, overweight, obesity, type 2 diabetes and disorders of the immune system, as well as with better cognitive development [5, 6].

There is no singular standard for breast milk composition: human milk composition is dynamic. Differences in the nutrient content of breast milk are observed within feeds, across the period of lactation (foremilk differs from hind milk, and colostrum is very different from transitional and mature milk) and between women [7, 8]. At least some of these changes in the composition of breast milk during lactation reflect changes in the requirements of infants, which are linked to changes in growth velocity and maturation of immunological and physiological functions. The complexity is also given by the diverse composition of breast milk. Nutrients (such as proteins, lipids, carbohydrates, minerals, vitamins and trace elements) are of high importance to meet the nutritional needs of young infants and ensure healthy normal growth and development, but human milk also contains numerous bioactive proteins and peptides including antimicrobial and immune-modulating factors, enzymes, hormones and growth factors [9, 10]. Several of these compounds affect the infant’s immune status, conferring a passive protection against infection, and facilitate immune development and maturation.

Although it is variable within mothers and across lactation, the macronutrient composition of human milk is conserved across populations. The mean macronutrient composition of mature, term milk is estimated to be approximately 0.9-1.2 g/dl for proteins, 3.2-3.6 g/dl for fat and 6.7-7.8 g/dl for lactose [11].

The proteins of human milk are divided into the whey and casein fractions comprising a large number of different proteins and peptides [12, 13]. The most abundant proteins are caseins, α-lactalbumin, lactoferrin, secretory IgA, lysozyme and serum albumin [9]. Nonprotein nitrogen-containing compounds, including urea, ureic acid, creatinine, creatine, amino acids and nucleotides, cover approximately 25% of human milk nitrogen.

Both total protein content and concentrations of individual protein...

Table of contents

• Cover Page
• Front Matter
• Hydrolyzed Protein in Infant Feeding
• Protein in the Feeding of Term Infants
• Protein in the Feeding of Preterm Infants
• Subject Index