What are the benefits of breastfeeding your baby? How do babies build up their immune system and gut flora from nothing? And, are there probiotics in breast milk?
While writing 7 Things You Didn't Know About Raw Milk, I kept racing down (fascinating — but mostly irrelevant) rabbit trails about breast milk. It got curious-er and curious-er. 😉 So I decided to write another blog post!
Let's explore a few of the ways breast milk affects development of the infant gut…
If you were or are unable to breastfeed your baby, please know that this is not a condemnation. It is an exploration of the wonders of breast milk — while recognizing that many women cannot breastfeed their baby for reasons outside of their control.
First: A Note On The Lymphatic System
Our discussion begins with the lymphatic system, which functions as a vital part of the immune system.
In case you need a refresher (me, too!), the lymphatic system transports fluid through the body. Similar to veins, it does this by moving fluid back to the bloodstream from the body's various tissues. But first, it filters the fluid through lymph nodes to remove any damaged cells, cancer cells, bacteria, or viruses — thus helping to protect the body from infection. (Source.)
The Entero-Mammary Pathway
Now, back to breast milk. Research suggests that the lymphatic system of lactating females ferries immunoglobulins (antibodies) from the gut-associated lymphoid tissue (GALT) to the mammary glands.
In other words, if you're a mother, the antibodies in your gut travel into your milk! This is called the entero-mammary pathway or the enteromammaric link.
So, how does it work?
Well, the GALT stores antibodies and other immune cells. It's significant because that 1 tissue actually contains up to 70% of all immune cells in the entire body. A huge part of your immune system is stationed in your gut!
When a pathogen is recognized in the gut, production of pathogen-specific antibodies begins. In males and non-lactating females, these antibodies travel from the GALT to the gut and other lymphatic glands to combat the pathogen. In lactating females, these antibodies travel to the mammary glands as well.
Breast milk actually contains all immunoglobulins — M, A, D, G, and E — although IgA is the most abundant. Once IgA arrives in the mammary glands, it gains a secretory component so it is resistant to digestive enzymes in the baby's gut.
And now for perhaps the most wonderful part: Mother and baby share the same epidemiological environment. The mother gives pathogen-specific antibodies to her baby. And, at least initially, her baby will most likely encounter the same pathogens as the mother. This preps the baby in the best way possible. (Source.)
Are There Probiotics In Breast Milk?
Although human milk was traditionally believed to be sterile, studies now show that lactic acid bacteria (aka probiotics) are present in breast milk. They may help the baby fight infections and encourage the development of a healthy immune system (source and source).
How do probiotics get into breast milk in the first place?
Well, we know that antibodies travel from the gut to the mammary gland via the lymphatic system, and then to the baby. Does the lymphatic system transport anything else?
The mother's vagina and skin contribute bacteria to her baby — and so can her gut. While still up for debate, intestinally-derived probiotic bacteria may travel through the lymphatic system to the mammary gland within a mononuclear phagocyte.
Other Protectors Of The Infant Gut In Breast Milk
While the baby's immune system and gut flora develop, what helps to keep bad bacteria at bay?
The presence of lactic acid bacteria and antibodies help, but that's not all. Breast milk has even more to offer…
Not only does this glycoprotein stimulate growth of the intestinal lining and prevent inflammation, but by binding with iron, it renders the metal unavailable to pathogenic bacteria.
We humans need iron — and so do most bacteria. Without iron, they are unable to grow. This means that lactoferrin can be termed bacteriostatic. I'm waiting for the day when I'll be able to use that word in casual conversation! 😉 (Source and source.)
Finally, we have the bifidus factor. Let's define a few terms.
The smallest unit of a carbohydrate is a monosaccharide — also known as a simple sugar. When 2 monosaccharides bond together, they form a disaccharide (such as the milk sugar lactose!). An oligosaccharide is a small number of simple sugars (but still more than 2) bonded together. Lastly, a polysaccharide is composed of long, sometimes nonlinear, chains of sugar molecules.
Now, let's put that information to good use. The bifidus factor is most likely an oligosaccharide that encourages the growth of Bifidobacteria (probiotics) in the infant gut.
While intestinal enzymes easily digest lactose in the small intestine, bifidus factor is indigestible and reaches the large intestine intact. There, it ends up as food for Bifidobacteria. This means that it is a prebiotic (read about the benefits of prebiotics here)!
Bifidobacteria then prevents the growth of pathogenic bacteria. (Source.)
In addition to feeding probiotic bacteria, the oligosaccharide portion of breast milk also seems to inhibit bad bacteria directly. It does this by preventing pathogens from attaching to the mucous membranes in the infant gut (source and source).
How Is Breast Milk Different From Other Raw Milks?
For one thing, while defense factors like IgA and lactoferrin comprise only 5% of bovine milk proteins, they make up to 30% of human milk proteins (source)!
Furthermore, human milk has a higher total percentage of fat and carbohydrate (mostly lactose) than cow milk and a lower total percentage of protein (On Food and Cooking, pg 13).
No doubt you agree, the benefits of breastfeeding are numerous! Breast milk provides protection from a number of infant diseases, and in some cases, this protection extends a number of years beyond infancy. A few such diseases include otitis media, respiratory tract infections, and diarrhea. (Source.)
And in addition to the immediate benefits of breast milk, according to this study, breastfed babies also have a lower risk of developing diabetes, obesity, cancer, and cardiovascular disease in later life. They also performed better in intelligence tests during childhood. These effects dilute with time. (Source.)
In closing, I will leave you with this quote:
“A pair of substantial mammary glands has the advantage over the two hemispheres of the most learned professor's brain, in the art of compounding a nutritious fluid for infants.” –Oliver Wendell Holmes, Sr.
Did you know about the benefits of breastfeeding? Did you know there are probiotics in breast milk? Have you breastfed, or do you want to breastfeed, your baby?
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