Human milk is a complex species-specific mammary glands’ secretion, which infants get through breastfeeding from their mothers as a complete source of nutrition until weaning (start of taking solid foods). Besides its nutritional part, it provides a degree of immunological protection to infants and decreases the rates of forthcoming diseases like diabetes and asthma. Hence it can be considered as a functional food, a food with an extra property of disease prevention. Human milk also supplies good bacteria to infants and has, in actuality, far more attractive healthful virtues. But, first we shall discuss the historical grey-shades of technical, social and microbiological understanding of human milk.
Past technical and social understanding of human milk
All of the human body fluids (urine, blood, saliva and spinal), except milk, have always been studied extensively during the course of development of medical physiology. Human milk, at first blush, has been considered as a readymade and readily available source of sugars, proteins and fats, in a ratio of 7:3:1, for infants. Although, it was told 130 years ago that breastfed infants have more chances of survival than bottle-fed ones, yet we could not attribute milk its due importance in child development. It is quite debatable, in fact, that why we took almost 100 years to realize the actual importance of human milk? Fifty years ago, researchers discovered the presence of oligosaccharides, a different sugar other than which is present in cow milk, in human milk, but couldn’t deduce its structural aspect in the absence of proficient techniques. This was the major reason behind the unexplored scientific status of milk at that time. According to a recent report published in science magazine, an eminent epidemiologist, from Cincinnati Children’s Hospital in Ohio, admitted that mother’s milk was “ignored as not modern”, across the globe, for past 50 years. Many research groups, including us in National Dairy Research Institute (NDRI, Karnal, India), face difficulties in getting human milk samples from citizens due to scientific unawareness and judgmental approach towards giving biological samples for research.
Past microbiological misbelief about mother’s milk
Microbiologically, human milk has always been supposed sterile and a milk sample from a woman with mastitis, an inflammation of breast tissue, was only considered positive for microbes. Moreover, mother’s milk was ignored, unfortunately, during the human microbiome project (HMP, U.S.A.-2008), where all human body samples, like fecal, skin, vaginal and nasal were analyzed for detection of diverse microbial communities together with the functions thereof.
Present advancements in knowledge regarding health benefits of mother’s milk
But now with an emergence of a technically advanced era, milk ingredients like human milk oligosaccharides (HMO’s) and their role in infant’s development have been identified. In recent years, breastfeeding has been encouraged across the continents both on socio-medical grounds and is regaining its vital importance for physical and immunological development of an infant. Moreover, emergence of “functional foods concept” ignited the exploitation of nutritional sources for their extra health benefits. All previous inevitable perceptions were catapulted at the bay after the growing interest of biologists in human milk microbiota (total live microbial content) and its microbiome (total genetic material of milk). Microbiologically, human milk is recognized, after the studies of Martin, McGuire, Rodríguez, Aagaard and Fernández et al., as a potential source of diverse range of beneficial microorganisms.
After an advent of advanced and high throughput technologies, mother’s milk has now been proved as a potential source of stem cells, vitamins, immune cells like macrophages and a throng of bioactive molecules (of protein, fat and carbohydrate nature). Human milk is also known for supplying to infant’s stomach, some proteins and inactive enzymes, which become active during gastric transit and provide a number of beneficial peptides (hydrolyzed parts of protein). A diverse range of physiological and immunological changes occur during late pregnancy, which construct, synergistically, a transfer route of mother’s intestinal good bacteria to mammary glands and finally into milk. These beneficial microbes are delivered to infant’s gut through breastfeeding. Bifidobacteria and Lactobacilli have cooperatively been considered as the guiding authority, comprising majority of good bacterial share of milk, and leads the healthier development of infant’s gut. At university of California, in 2006, a research group identified 200 types of HMO’s. But, these were revealed indigestible for humans then what could be the significance of having that sugary cocktail in mother’s milk. Answer came after a German report, that Bifidobacterium longum biovar infantis, a predominating early settler to infant’s gut, was found to harbor, on its DNA, all genes required to use that sugar mixture in milk. Hence, Bifidobacteria were recognized to be the sole utilizer of all those peculiar sugar types. This microbe in turn supports the growth of other beneficial bacteria, like Lactobacilli, and mutually promotes a healthier expansion of intestinal immune system. Moreover, these milk bacteria make fatty acids, outperform bad bacteria and educate infant’s immune status in a right way. Researchers theorize, on microbiological point of view, that mother’s milk offers a nutritious cocktail of good bacteria and employs these workhorses as a guiding model for healthier wellbeing of infant. This is a classic example of mother’s care to their infants, right from the start of their post-delivery lives. According to a recent review from “Nature” journal, primary establishment of infant’s gut bacteria has been considered important for the possible susceptibility of infants towards immunological disorders in the later stages of their lives. Besides milk sugar’s role as a nutrition to good bacteria, they have, itself, been found to decry many harmful bugs (Salmonella, Listeria, and Campylobacter), which would, otherwise, be causing deadly illness in premature and weak newborns. The transient presence of human milk microbiota in mammary glands, just for lactation period, can describe the rational importance of mother’s supply of beneficial bacteria to infant’s gut for better development of their immune system. Human milk, endowed with a myriad of nutritional factors, bioactive molecules and health promoting bacteria, can be considered as a “natural functional buffet” for infants and makes us to arrive at the conclusion that breastfeeding is nature's health plan.