Breastfeeding, Immune Function, and Healthy Gut Bacteria

Written by:

Maia James


Earlier today, my husband, Daylon, sent me an article about a new study that shows that breastfeeding is linked to a healthy gut in infants because of the way specific genes are expressed. While the conclusions of this study are fascinating, the details are esoteric and the article is too science-y for me.

Since Daylon has a Ph.D. in molecular embryology and works in the medical field, I asked him some questions that helped me understand the crux of this article. Here’s what he had to say:

Most people are aware of the connection between the flora in your gut and your general gastrointestinal health (see: fecal transplants as a treatment for IBS) as well as the capacity for the flora in our bodies to regulate healthy homeostasis (see: why antibiotics result in yeast infections).

People are also generally aware of the notion that lack of proper immune stimulus (e.g., bacterial/viral infections and/or exposure to allergens) can result in poor immune responsiveness in adulthood and/or allergies. Indeed, many lines of evidence have been presented in recent years supporting the hypothesis that a childhood of exposure leads to a healthy immune system; another vivid example is the one involving pigs in mud versus clean pigs.

Ok, I’m with you. But get to the part about THIS study. 

Basically, this breastfeeding study builds on what everyone already knew, but in a different context. Because the intestinal epithelia (the skin lining the inside of the intestines) is shed in feces at an astonishing rate (one-sixth of its total each day), you can examine the “expression profile” of those cells. At the same time, you can also measure the types of bacteria that are colonizing the gut by virtue of their own non-human “expression profile.”

Ok, so what did the study find?

These researchers made two important discoveries:

  1. There were more types of microbes present in the gut of a breastfed baby.
  2. In spite of this putatively “pathogenic” finding (more flora is often mistakenly presumed to equal a more virulent burden), the immune response in the intestine had adjusted to cope with the increased diversity of flora. The researchers can tell how the cells in the gut are responding because they are shed in the feces, from which they can be isolated and tested. 

By tying these points to other studies of immune capacity and early exposure to bacteria, it is reasonable to believe that the lack of bacterial diversity in the formula-fed gut may result in imbalances in the acute phase (an interesting though data-light explanation for colic), but more importantly, may result in long term complications surrounding the health of the gastrointestinal and immune systems.

So is it the absence of breast milk or the presence of formula that causes problems (and vice versa when it comes to the benefits)?

I’m sure that the natural balance of sugars in breast milk are suitable for a range of biota, while formula either negatively or positively selects for a subset, leaving an unbalanced repertoire that leads to a relatively incomplete immune stimulus.

While Daylon’s synopsis may still be a little dense for some of us (I secretly just had to look up the word “putatively”), I understand the gist of the article now, and I think this is further incentive for mothers to breastfeed for at least the first year.

Stay sane,

Maia, Founder & CEO

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