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How gut bacteria arrive in breast milk to form milk microbiome

gut residents being immunoported to the breast

Breast milk contains around 1000-10 000 bacteria / per ml. So where do the bacteria come from ? YOUR GUT. Surprised ?

You’re committed to breast feed. Awesome – you’re giving your baby the perfect mix of nutrients and “things”, to ensure baby grows up BIG AND STRONG.

Shoo, the list of extra goodies, mother nature is packing into breast milk is pretty long. It includes,

Nucleotides
Fatty acids
Immunoglobulins (antibodies)
Glycoproteins (HMGPs)
Cytokines
Immune cells
Lysozyme
Lactoferrin
Immunomodulatory factors such as exosome and micro-RNAs
Stem cells
Oligosaccharides

And bacteria.

The life force in milk

Breast milk contains around 1000-10 000 bacteria / per ml, these bacteria are the milk microbiome.

Don’t panic………… they’re not the kind of bacteria, that cause disease, these are good guys. They will become your baby’s microflora, the collection of bacteria that teach your baby’s immune system, the A B Cs.

Who to AVOID.
Who to BEFRIEND
Who to CULTIVATE

Getting this right, will help baby fight infections, avoid auto-immune disorders and minimize metabolic troubles, for the rest of their life.

In fact, they are so important, this is the reason breast milk comes loaded with oligosaccharides, it is the third most prevalent nutrient in breast milk (each litre has between 5-15 g of oligosaccharides). The oligosaccharides aren’t providing nutrition for your baby, they’re there to feed the bacteria, so they are happy and healthy.

So where do the bacteria come from ?

The BIG migration

YOUR GUT.

Surprised ?

Scientists are just beginning to piece together the details of the great migration. It is an epic journey, requiring the bacteria to

First escape the intestine, by crossing the intestinal epithelium.
Then, they must evade the immune system and reach the mammary gland.
Finally, they must squeeze across the epithelial membranes in the breast tissue, landing in the milk….
To finally be slurped down, when baby suckles.

So how do they do it ?

They’re being IMMUNOPORTED

Bacteria are too small and vulnerable to make this big move unsupported.

The evidence suggests they’re being deliberately transported by the immune system. The cells doing the IMMUNOPORTING are a specialized type of cell, known as the dendritic cells. Dendritic cells big job, is to survey the body and collect information about who is around. They then, pass this information to the T-cells, who respond appropriately.

Which usually means, they come out guns blazing.

But, in this case, the dendritic cells, dump their LIVE cargo, in the breast tissue.

Hormones process the live cargo

How they manage to arrive ALIVE is still a mystery. It is suspected that progesterone, ensures they are not “digested” by the dendritic cells, prior to arrival.

They arrive at the breast, just as the milk production machine, is about to go on line.

The breast re-construction process, designed to ensure the breasts are big enough and ready, to keep junior supplied with nourishment, is largely complete. Prolactin, the foreman in charge of “Operation MILK”, has made the nipple and areola larger, the ducts and alveoli have all been extended and the blood supply enhanced.

In the final stages of lift off, prolactin gives the order to the claudin proteins inside the tight junctions – to loosen their grip. The epithelial cells move apart……………… making the epithelial layer permeable enough to allow milk to slip through.

Finally, the oxytocin surge, which is designed to push baby out, also causes the mioepithelial cells to contract, pushing the bacteria through the layer.

Plop, plop……………………. thousands of bacteria are “winging” their way to baby.

The colostrum is especially full of bacteria, but the bacteria continue to be sent to baby, ensuring baby develops a healthy microflora.

It’s only healthy if you’re healthy

Which bacteria make the epic journey ?

Scientists are not sure……………. they do know, every Mom has a unique milk microbiome.

And since it begins with your gut. Your milk microbiome is going to be related to your gut microbiome. So…………….. you need to ensure you’re feeding, seeding and not accidentally or deliberately, weeding your gut microbiome unnecessarily – to ensure your milk microbiome, is healthy.

Human milk: a source of more life than we imagine. Beneficial Microbes (2013) 4(1): 17-30. P.V. Jeurink, J. van Bergenhenegouwen, E. Jiménez, L.M.J. Knippels, L. Fernández, J. Garssen, J. Knol, J.M. Rodríguez and R. Martín.