Milk, Microbes and the importance of Breast-feeding

Milk, as you may know, is a mammalian feature, with variants accordingly to the specific needs of each species. But from what is it made of? And which is its function?

What’s milk?

Although diurnally variation of human milk composition over lactation and between mothers, we can divide it up to three major parts, namely: carbohydrates (mainly lactose, 70 g/L), lipids (40 g/L) and H.M.O.s (Human Milk Oligosaccharides, 5–15 g/L). These oligosaccharides, as complex sugars, were perfect to be used by babies as energy sources. Nevertheless, babies do not digest them imposing a pertinent question — Why do we need them for?

The “why’s” were pilling up and, in 1954, Richard Kuhn together with Paul Gyorgy found out that, after H.M.O.s passed by the stomach and small intestine unharmed, arrived to the large intestine, where most of our bacteria live, to nourish them.


All of them? No. In 1990, Bruce German identified all the H.M.O.s and tried to fed them to bacteria to find out which sugar fed which microbe. Nothing grew — they thought. Sixteen years later, the same team discovered that the oligosaccharides had, after all, specific targets, mainly Bifidum longum infantis.

The human microbiome is formed by a wide set of microorganisms living in association with the human body. Being almost sterile inside the womb, an infant’s gut is rapidly colonized as soon as it is out by thousand of bacteria species transferred from mother to child through birth and breastfeeding. With food coming in, B. infantis comes up to be our dominant microbe, teaching our immune system how to respond on the presence of several bacteria species — friendly ones and pathogenic ones. Besides, B. infantis produces biotin, vitamin B12, pyridoxin and, in far greater amounts than most of the other species in the Bifidobacterium family, thiamine, nicotinic acid and folic acid.

Later on, new experiments lead to new conclusions: H.M.O.s are not just food for bugs. H.M.O.s may be antiadhesive antimicrobials that, working as soluble receptors, induce pathogen attachment to them rather than to infant mucosal surfaces, hence lowering the risk for infections. Moreover, H.M.O.s, between other things, may be a sialic acid source for the child — helping the development of the brain and cognition.

To keep in the mind: formula feeding or cow milk, between others, although good solutions for mothers with no milk, do not provide the new born with the essential tools for their full development. If you can, breastfeed. Is important to remember that bacteria present in breast milk are among the first microbes entering the infant body, having a main role on microbiome establishment in the newborn and, consequently, in their health.

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