Breastmilk And A Baby's Immune System
Breastfeeding has occurred over aeons. It’s normal for our species.
Many of us know breastmilk 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 breastmilk 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 breastmilk during babyhood.
Indeed, there are many possible ways breastmilk 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 for making 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: Breastmilk May Induce Local Immunity
There are many anti-infective and anti-inflammatory factors in breastmilk. Some of these factors (secretory IgA and lactoferrin) can be found in higher amounts 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 breastmilk 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: Breastmilk Is Not Sterile – For 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.
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.
Breastmilk also contains prebiotics (the food for the bacteria). In fact, the third most abundant component in breastmilk are oligosaccharides (prebiotics) and breastmilk has over 200 kinds!
Bacteria transferred to the baby when breastfeeding may help to stimulate the baby’s immune system to grow.
#4: Breastmilk Growth Factors May Help Develop A Baby’s Gut
Breastmilk contains many growth factors. Some of these growth factors (e.g 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: Breastmilk May Promote Oral Tolerance
Oral tolerance is when one’s immune system does not react when orally exposed to something that should be harmless (e.g. food).
Breastmilk contains a variety of potential allergens sourced from the mother’s environment (e.g. various food proteins). The presence of these in addition to the various immune modulating properties of breastmilk could mean breastmilk plays an important role in the development of oral tolerance.
Hence, breastmilk may be an important aspect to help prevent allergy and autoimmune diseases.
Science is really only beginning to unravel some of the complexities about breastmilk. It’s clear 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, breastmilk, since the beginning of human existence.” — Gabrielle Palmer
“Human milk is not a food… It is a highly specialised infant support system.” — Dr Stephen Buescher