5 Ways Breast-Milk Is Important For The Immune System.

Breastfeeding has occurred over eons and is normal for our species. Many of us know breast-milk is important to support a baby’s immune system. Some of us are aware that not breastfeeding increases the risk of infection. However, many people think breast-milk only helps support a baby’s immune system while he receives it. Surprisingly, this is not quite true. In fact, there are many longer term health risks associated with not breastfeeding. Part of this is likely due to the lack of breast-milk during babyhood. Indeed, there are many possible ways breast-milk is important for the immune system in the long term.
Here are 5 of them:

1. Larger Thymus Gland:
Breastfed babies tend to have larger thymus glands than formula fed babies. Or, formula fed babies tend to have smaller thymus glands. The thymus gland is the central organ of the immune system. It’s important in the production of white blood cells, which are an important part of our immune defence. It also makes other cells (regulatory T cells) which are important to help prevent autoimmune diseases. A larger thymus gland may be an important factor for optimal functioning of our immune system long term.


2. Breast-milk May Induce Local Immunity:
There are many anti-infective and anti-inflammatory factors in breast-milk. Some of these factors (secretory IgA and lactoferrin) can be found in higher amounts in the urine of breastfed versus formula fed babies. This may be a reason why formula fed babies have an increased risk of urinary tract infections. This is evidence that breast-milk induces local immunity in the urinary tract of breastfed babies because the size of proteins such as secretory IgA and lactoferrin are too big to be able to be filtered by the kidneys. Hence, it’s possible they get there by greater production of immune factors in a breastfed baby’s urinary tract.

3. Breast-milk Is Not Sterile – For A Good Reason:
More research than ever is highlighting how our gut microbiome (the microbes such as bacteria and their associated immune cells in our gut) play an important role in our health. Although we don’t know exactly how, we know that early life events (example- how we are born and fed as babies) play an important role in developing the microbiome.

In its early stages, the gut microbiome is highly plastic (meaning it can be easily altered) and influenced by the effects of early life events. As the baby develops, the gut microbiome loses it plasticity and becomes more resistant to change. This may ‘lock in’ an ideal or a non-ideal gut microbiome well into adulthood. Breastfed babies take in bacteria from the mother’s skin and in her milk. These bacteria are the beneficial type which make a home in their gut and on their skin, helping to keep them healthy by developing a healthy gut microbiome. Breast-milk also contains prebiotics (the food for the bacteria). In fact, the third most abundant component in breast-milk are oligosaccharides (prebiotics) and breast-milk has over 200 kinds! Bacteria transferred to the baby when breastfeeding may help to stimulate the baby’s immune system to grow.

4. Breast-milk Growth Factors May Help Develop A Baby’s Gut:
Breast-milk contains many growth factors. Some of these growth factors (example- HCF and EGF) may assist with the development of the gut including its lining. This could be an important part of how breastfeeding helps a baby’s gut to maintain its integrity and prevent pathogens from getting through.

5. Breast-milk May Promote Oral Tolerance:
Oral tolerance is when one’s immune system does not react when orally exposed to something that should be harmless (example- food). Breast-milk contains a variety of potential allergens sourced from the mother’s environment (example- various food proteins). The presence of these in addition to the various immune modulating properties of breast-milk could mean breast-milk plays an important role in the development of oral tolerance.

Hence, breast-milk may be an important aspect to help prevent allergy and autoimmune diseases. Science is really only beginning to unravel some of the complexities about breast-milk. It’s clear that breastfeeding plays an important role in the development of the immune system both in the short and long term.

On a final note, here are some really interesting quotes:
“If a multinational company developed a product that was a nutritionally balanced and delicious food, a wonder drug that both prevented and treated disease, cost almost nothing to produce and could be delivered in quantities controlled by the consumer’s needs, the very announcement of its find would send its shares rocketing to the top of the stock market. The scientists who developed the product would win prizes and the wealth and influence of everyone involved would increase dramatically. Women have been producing such a miraculous substance, breast-milk, since the beginning of human existence.” — Gabrielle Palmer

“Human milk is not a food… It is a highly specialized infant support system.” — Dr Stephen Buescher.