What Role Does the Microbiome Actually Play in Human Development?
We’ve posted many fascinating articles about the microbiome and its relationship to personal hygiene, obesity, antibiotics, mental health and much more. But let’s take a moment to go back to basics (and back to birth) to review how decisive the microbiome is in human development.
From the moment you were born, your microbiome was growing up alongside (or rather, inside) you! Your mother and, if you were nursed, her breastmilk is where it all began. Scientists believe the first three years of life are the most crucial for our developing microbiomes. So instead of eating birthday cake, ring in baby’s first birthdays with a breastmilk-shake instead! OK, fine, with whipped cream and a cherry on top.
If you were taking a pop quiz on the basics of the microbiome, you would profit greatly from reading a recent article titled “Role of the Microbiome in Human Development”, published by Prof. Maria Gloria Dominguez-Bello, Filipa Godoy-Vitorino, Rob Knight, and Martin J Blaser (a New York University research professor). In this article, we’ll summarize the highlights of their paper, in which they take stock of all the known ways the microbiome impacts human development, beginning with 1) our evolution, 2) maternal/ fetal relationships, and 3) future perspectives on the microbiome’s impact on our nutrition and growth.
The Circle of Life: Evolution and Birth
As mentioned above, individual human development from birth onward involves microbiota, but did you consider that the entire human species development couldn’t have happened if it weren’t for microbiota? The microbiome co-evolved with humankind, and in turn shaped phenotypes in our ancestral lineage. Phenotypes refer to our actual physical characteristics: visible ones like height and eye color, but also overall health, disease history, and even our temperament! The authors put it thus, and how poetic it sounds!
The microbiota occupies the interface between our bodies and the exterior, and interactions with the environment (including diet, sun-light, bathing, cosmetics) cross this interface. The microbiota is at the same time self and non-self […].
If an interface is a point where two systems meet and interact, it may be helpful to think of microbiota as porters to an apartment building that is our body, keeping close tabs on who (or rather what) strolls in from outside.
The microbiota of the fetus’s mother affect the fetus indirectly
Now let’s zoom back in to look at the microbiota of the individual. In mammals like humans, the womb is immune protected, which means bacteria cannot colonize inside it: the uterus, fetus, and placenta appear free of any microbiota. The microbiota of the fetus’s mother, however, affect the fetus indirectly. Labor and birth “mark the first major exposure to a complex microbiota and is the primordial mechanism for intergenerational microbiota transfer in mammals”. How does one generation (mother) pass microbiota on to the next (baby)? It’s all in the anatomy. The birth canal is adjacent to the rectal canal, which allows for transfer of the mother’s gut and vaginal microbiota to her child. For this reason, C-section delivery as well as any administered antibiotics during vaginal delivery alter bacterial colonization in the baby. The transfer doesn’t stop there: breast feeding, according to the authors, enables development of the sensory and motor capabilities of the brain in babies at a level that is nothing less than remarkable.*
And After We’re Born?
Early human development doesn’t play out inside a bubble. Human density, home architecture, ventilation, diet, clothing, exercise, personal care products and medicines, but also where in the world you live all factor in. So how does one maintain a “healthy” microbiota for themselves and their children in this industrial urban world? The authors conclude by urging for more studies that assess how well the microbiome matures across a population of healthy individuals compared with disease states, in the same way that science has already charted norms for maturation of height and weight in children — “essentially a growth curve for the developing microbiome.” Only then can we learn associations between disturbances to the microbiota, host responses and diseases in the hopes of restoring them for our future generations.
*To understand more on the development of a baby’s gut bacteria in the first three years of life, see article