Jun Kim Ph.D.

Recently breast milk even seems to have become a significant commodity with for-profit companies such as Prolacta Biosciences processing 2.4 million ounces in 2014, which compares to 3.1 million ounces dispensed in 2013 by all 18 nonprofit milk banks in the Human Milk Banking Association of North America. Such high demand may be justified given that the human milk has been considered as the gold standard for infant feeding throughout history and across different cultures, although there seems to be some questionable applications[1]. Despite the extensive literature describing advantages of human milk it still surprises scientists with new discoveries that allow a glimpse of how perfectly it is made for newborns[2].

It is widely acknowledged that there are many benefits in breast feeding that are physiological, environmental, socioeconomic, as well as psychological[3]. Well-controlled scientific analysis of breast feeding is inherently challenging, because it is unethical and practically impossible to conduct a double-blind randomized trial comparing breastfeeding and formula feeding. Yet, reduction in infection rates is a widely recognized health benefit of breastfeeding. According to the American Academy of Pediatrics (AAP), any breastfeeding reduced the risk of gastroenteritis by 64% and of otitis media by 23%[3]. Further, exclusive breastfeeding for more than 4 months reduced the risk of lower respiratory tract infection by 72%[3]. There are also studies showing benefits of breastfeeding in neurodevelopment, obesity, allergy, and autoimmune disorders, but mostly they are observational studies and require better controls for more reliable results[3–6].

In addition to carbohydrate, protein, and fat, breast milk provides vitamins, minerals, digestive enzymes, and hormones. Breast milk also contains human milk oligosaccharides (varies between women), antibodies and lymphocytes from the mother that help the baby resist infections[7]. Such components seem to be individualized for each infant. When the mother comes into contact with the baby and subsequently, the pathogens that colonize the baby, she then makes the appropriate antibodies and immune cells that can be passed to her baby through her breast milk[8]. More antibodies are found in the initial milk produced, named colostrum, and this helps to protect the newborn until its own immune system is functioning properly[9]. Therefore, some of the key health benefits from breastmilk is personalized for the baby and comes not only from the dietary nutrition but also from interactions with the mother.

Breast milk is not sterile but contains as many as 600 different species of various bacteria, including Bifidobacterium breve, B. adolescentis, B. longum, B. bifidum, and B. dentium[10]. These bacteria can come from the baby’s mouth, but more intriguingly they can also come from the mother’s gut. Studies suggest that immune cells in the mother’s gut can pick up bacteria and carry them around the body using the lymphatic system[11]. These cells can then end up in the mammary glands and eventually in the breastmilk. A study showed that in 1 day-old newborns Enterococcus and Streptococcus were the microorganisms most frequently isolated[12]. From 10 days of age until 3 months, bifidobacterial become the predominant group. Lactobacilli and bifidobacterial are some of the most common bacteria found in breast milk and may contribute to the initial establishment of the microbiota in the new born.

Probiotics isolated from breast milk are suggested to have various health benefits. Some of the strains have been shown to produce anti-microbial compounds to inhibit the growth of E. coli, Salmonella spp. and Listeria monocytogenes[13]. It has also been shown that they can improve the intestinal barrier function by reducing intestinal permeability[13]. Most importantly they compete with entero-toxigenic bacteria for nutrients and for colonization sites[14]. Clinical studies such as those involving L. reuteri and L. salivarius show various benefits when treated[15,16]. Furthermore, these probiotics are some of the first microorganisms that the newborns contact, which is crucial for determining the subsequent course of immune system development[11]. Probiotics are known to induce a TH1 response, and down regulate the production of TH2 cytokines, responsible for the allergic response[17]. Also a clinical trial showed that supplementation of infant formulas with rhamnosus LGG improved neonate growth pattern[18].

Cellular and molecular insights on how human breast milk and breastfeeding influence child development are important, because they can lead to novel therapeutic approaches. For example, molecules and probiotic species discovered in human breastmilk have shown promising results in clinical studies for diseases such as cancer, inflammation, and infections[13,19,20]. Many of these probiotic species are already being used in infant formula or dietary supplements, and it would be exciting to see more active uses as actual treatments. However, it is also important to keep in mind that some of the benefits cannot be artificially generated with a few ingredients as they involve a genetic, molecular, and psychological interaction between the mother and the child.

Sources

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