Breastmilk - a baby's first defense mechanism

by Heidi Lam
LLL Hong Kong - Chinese Group

We live in a world full of micro-organisms such as bacteria, viruses and fungi. Bacteria exist all over the human body – on the skin, in the gut and in the mucosal membranes. These are needed for a normal life. When we look closely into the immunology of breastmilk, it is amazing how Mother Nature protects our babies to survive in this bacteria-filled world.

Born naturally: from sterile to germs 
Babies live in a rather sterile environment inside their mothers’ wombs. Suddenly, one day, the baby is born right next to the mother’s anus – an area teeming with bacteria. Next, the baby is put onto the mother’s chest and licks her skin – bringing him into contact with a new range of bacteria. 

So what happens to all those germs? These are actually normal bacteria or microflora that will colonize the baby’s skin, gut and various mucosal membranes. The microflora will prevent the growth of dangerous bacteria by competing with them for nutrients and space. In the baby’s gut, the normal bacteria flora is composed of more “good” bacteria like bifidobacteria and lactobacilli, and less “bad” ones such as E coli and Staphylococcus aureus. 

However, human babies are born very immature compared to other mammals. Their body systems are still developing and the epithelium lining of the infant’s gut is not yet intact. This means germs and antigens may get through the “holes” of the “leaky gut” and enter the bloodstream and body tissues. 

If this happens, a war erupts between the bacteria and the baby’s still-immature immune system. The baby defends his body against the “invader” and starts a series of reactions. 

The baby needs to use a lot of energy to fight this war, so normal growth and development may be compromised. If the baby’s system is not capable of reacting properly, the baby may get sick. 

Breastmilk defenses 
Let’s go back to the newborn. The tiny baby moves over his mother’s chest and touches her nipple. He latches on and gets colostrum in reward. 

Having contact with so many germs right after birth, the baby initially has a far greater need for immunological protection than for nutrition. Mother Nature is well aware of this! Colostrum is produced in small quantities, but it has a high concentration of a major protein component called SIgA antibodies. SIgA antibodies in breastmilk are specific to the mother’s gut bacteria. 

Can you see how lucky it is that baby is born next to mother’s anus? Being born in this location means he gets the same bacteria as his mother, which the SIgA antibodies are targeting. 

Components work together 
Other breastmilk protein components, such as lactoferrin and lysozyme, work together with SIgA to protect the baby. Moreover, carbohydrates called oligosaccharides act as food for the “good” bacteria and enhance the growth of bifidobacteria and lactobacilli. More “good” bacteria in the gut means less space and food for the “bad” pathogenic bacteria to grow. 

This is excellent news for the baby’s still-immature immune system. Breastmilk fights the enemies before they can enter the bloodstream and tissue. Infection is avoided and the baby does not need to react with inflammation, tissue damage, clinical symptoms, nor to lose energy. War is avoided! 

The importance of normal gut bacteria 
This initial contact between the mother’s bacteria and breastmilk is a good learning opportunity for the baby’s immune system. Normal bacterial colonization in the baby’s gut significantly stimulates the growth of his immune system, which learns how to defend the baby from infection. It also learns not to overreact to normal substances such as food or pollen, which may otherwise induce allergic reactions. 

See what a perfect system has been created by Mother Nature! 

The risks of tampering with nature 
Now let’s consider another scenario. If a baby is born via Caesarean section, he doesn’t come into contact with mother’s gut flora near the anus. Hospital routines may cause the baby to be separated from his mother and placed in a nursery. The baby will be handled by various members of hospital staff. If breastfeeding is delayed he might not feed well and most likely he will be given formula milk. 

In this case, the baby has undergone a colonization of bacteria which are different to those of his mother. He has come into contact with germs from other people, but the SIgA antibodies in his colostrum can’t fight these “strangers” as effectively as the well-known germs from his mother. What’s more, the early start of artificial feeding means the baby does not have the supply of necessary SIgA and other factors to promote the growth of “good” bacteria in the gut, nor to help kill and block out pathogenic bacteria. The baby’s immune system is still immature, so when some bacteria attach to the mucosa in the gut or urinary tract, they may cause infection. 

A war is being fought between the baby’s immature immune system and the germs. 

Furthermore, cow’s milk protein, found in formula milk, is a common allergen. It may leak through the immature gut and enter the bloodstream, causing an allergic reaction. 

By comparing these different scenarios, we can see breastfeeding is a natural way to defend our babies against all the bacteria out there. Of course a Caesarean section is sometimes necessary, and many babies born this way still manage to breastfeed. However, it’s useful to be mindful of the effects of giving birth in too sterile an environment. To combat the absolute hygiene required by the operating theatre during a C- section, some practitioners advise wiping some of the mother’s amniotic fluid onto the baby’s body in order to recreate a more natural birth environment. 

Our world is teeming with bacteria. Breastmilk and a vaginal birth encourage the work of the “good guy” bacteria – which keep the “bad guy” bacteria at bay. 

​​​Close to the Heart Vol. 14, No. 2 (Mid-Year 2013)

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