Mothers’ Milk—Can We Improve the Neonatal Immunity Response With the Oldest Recipe in the Mammal’s Cookbook?*

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The first mammals appeared about 225 million years ago in the late Triassic epoch, and they expanded out of their nocturnal insectivore niche from the mid-Jurassic era onwards (1). During the Cenozoic era that began 66 millions years ago, mammals then took over the medium- to large-sized ecological niches and evolved into the current day diversity (2). Accordingly, from an evolutionary perspective, it would appear that the recipe for mother’s milk is very old indeed in the animal kingdom.
Mothers’ milk is essential for the survival of all mammals and even marsupial newborns, and until recent technological advances of modern medicine allowed for the development of nutritional alternatives, this also included humans. Still, the concentrated, first drops of human milk, the colostrum, contain not only nutrients but also equally rich in immunocomponents (3). Indeed, the colostrum contains the major component of the innate immune system, such as lactoferrin, lysozymes, lactoperoxidase, complement, and protein-rich polypeptides (4). Equally, a number of cytokines such as interleukins, tumor necrosis factor, and chemokines are present in the colostrum (5). Colostrum also contains components of the adaptive immune system, such as lymphocytes and antibodies like immunoglobulin A (IgA), IgG, and IgM.
It would seem, from an immunologic viewpoint, that colostrum serves a far greater purpose that simple nutrition. Yet, ironically, it may be that the population of neonates who need it the most, the very low birth neonates, also is the population who is unable to breastfeed or even tolerate large amount of enteral nutrition if given passively. Among others, the premature neonate is at increased risk of infection and immunologically associated illness such as necrotizing enterocolitis (NEC). It is therefore interesting from an evolutionary perspective that nature seems to have adapted to the situation in the case of a premature birth, as studies show that the colostrum of mothers who give birth prematurely is structurally different and for instance, contains elevated concentrations of lactoferrin for several weeks postpartum (6).
Naturally, much scientific endeavor has gone into elucidation: the relationship between the immature immune system of the premature child, the subsequent risk of immunologically associated illnesses, and the potentially beneficial effects of colostrum. Oral administration of colostrum to premature is feasible (7), and studies show that it may reduce the time required for achieving full enteral feeding (8) but also modifies the oral microbiota (9) among other positive effects on the immune system (10).
In this issue of Pediatric Critical Care Medicine, Zhang et al (11) report a randomized controlled study comparing the effects of orally administrating small doses of maternal colostrum on secretory Ig (sIg) and lactoferrin in very low birth weight infants. In this single-center study of 32 cases and 32 controls, the newborns weighing less than 1,500 grams at birth received either a small amount of their mother’s colostrum or saline during a period of 7 days. The subsequent measurements of sIgA and lactoferrin in saliva and urine aimed to explore the local and systemic effects of the orally administrated colostrum. Zhang et al (11) succeeded in demonstrating a modest difference between the groups, as there was a slightly higher saliva level of sIgA in the intervention group and an increased saliva level of lactoferrin over time in the intervention group. Furthermore, the authors report a nonstatistically significant tendency for lower prevalence of NEC, sepsis, and less days needed to reach full enteral feeding in the intervention group.

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