Nutritive and Bioactive Proteins in Breastmilk

Abstract

Protein ingested with breast milk provides indispensable amino acids which are necessary for new protein synthesis for growth and replacement of losses via urine, feces, and the skin. Protein gain in the body of an infant is highest during the first months when protein concentrations in breast milk are higher than during later stages of lactation. Low-birth-weight infants have higher protein needs than term infants and need protein supplements during feeding with breastmilk. Based on our better understanding of protein evolution in breastmilk during the stages of lactation, new infant formulas with lower protein concentration but better protein quality have been created, successfully tested, and are now available in many countries. Besides providing indispensable amino acids, bioactive protein in breast milk can be broadly classified into 4 major functions, that is, providing protection from microbial insults and immune protection, aiding in digestive functions, gut development, and being carriers for other nutrients. Individual proteins and their proposed bioactivities are summarized in this paper in brief. Indeed, some proteins like lactoferrin and sIgA have been extensively studied for their biological functions, whereas others may require more data in support to further validate their proposed functions.

A randomized controlled trial protocol comparing the feeds of fresh versus frozen mother’s own milk for preterm infants in the NICU

“…Carbohydrates, particularly human milk oligosaccharides (HMO), are important for protection against infection, particularly NEC [29]. Furthermore, a multitude of proteins are present in human milk that form its essential nutrition and also play contributory roles in infant immune protection as well as the development of the immune system and the gut [30,31]. Lipids come in many different forms and provide a major source of energy found in human milk [32].…”

Distinct roles for the mTOR pathway in postnatal morphogenesis, maturation and function of pancreatic islets

“…Beyond the scope of the current study, future experiments will need to identify the key regulators upstream of mTOR that stimulate this pathway in response to enteral nutrition. We hypothesize that there could be many direct and indirect sources of mTOR activation, including components within the mother's milk and amino acids such as leucine (González and Hall, 2017;Haschke et al, 2016;Millward, 2012). In addition, the connection between enteroendocrine cells, the neuroendocrine system, and the endocrine pancreas in regulating global nutrient homeostasis has been well documented (Heijboer et al, 2006).…”

Human milk: composition and health benefits

“…Indeed, proteins are essential to allow for infants' healthy growth but they act also as carriers for other nutrients (i.e., lactoferrin, haptocorrin, alfa-lactalbumin, folate-binding protein, beta-casein), promote gut development (growth factors, lactoferrin) and nutrients absorption (bile salt-stimulated lipase, amylase, alfa1-antitrypsin), and possess immune and antimicrobial activity (lactoferrin, secretory IgA, osteopontin, cytokines, lysozyme, etc.). 12 Milk proteins can be grouped into three major classes: caseins, whey and mucins. Caseins are assembled in micelles whereas whey proteins are present in solution.…”

“…Taken all together, these data suggest that proteins are involved in the mechanisms responsible for the beneficial health effects associated with breastfeeding, such as the reduced risk of developing morbidities, particularly infections. 12,13 Increasing evidence indicates that the quantity and the quality of protein in human milk play a crucial role in modulating infant growth and body composition. A high protein intake in infancy has actually been associated with an increased weight gain and risk of developing obesity later in life through the activation of the insulin-like growth factor-1 axis.…”