Nature vs. nurture. What is it that shapes our microbiome?
Gut microbiota represent a changing ecosystem that is continuously tested by many factors such as unbalanced diet, stress, antibiotic use...
What determines my microbiome? Our hair color, height, lactose (in)tolerance, and much more truly depends on our genes. But, when it comes to one's microbiome, genetics play less of a role. To a great extent, our microbial composition is environmentally driven.
What makes a healthy microbiome? Scientists accelerated research on the human gut microbiome when they realized that healthy and unhealthy individuals have vastly different gut flora. They wondered why. Healthy individuals tend to show a greater 1) diversity and 2) abundance in the composition of their gut flora.
What does diversity and abundance mean? Give me an example! Imagine your microbiota as a painting, where “gut bug” type is shown as a colorful dot. Various and healthy bugs will look like a painting with a plethora of colors. Few and uniform bugs will add up to a chunky, gray monolith. To be healthy, you want a lush landscape by Georges Seurat, not a pencil sketch by Picasso.
How can I achieve a healthy microbiome? Fortunately, you can steer the composition of your microbiome. Studies have shown large intra-individual variations in the microbial composition, meaning that the composition is bacterial strains is flexible and adaptable. The exact time-line of this adaptation is still being researched, but there likely are micro- and macro-variations in the microbiome composition.
When does my microbiome change? The microbiome evolves your entire life, with your core microbiota population shaped already during your infancy. You start as a blank slate – the intestines of the new-born are sterile and devoid of any bacteria. But, right at birth, the environment takes over: The newborn is immediately populated by the microbes from their mother's vaginal, fecal and skin microbiome as well as from the environment where they are delivered. The first exposure to the outside world largely determines the starting point of the microbiota profile. To recycle the metaphor from earlier, this is where the size and palette of our microbiome painting is set up. Logically, infants born via vaginal route have a more diverse microbiome compared to the C-section babies. This diversity is believed to be beneficial and protective right from the start. By the age of 3, child's gut flora is comparable in composition and diversity to those of adults. As we get older, our gut population becomes relatively stable. This stability is largely environmentally driven – we develop a diet and lifestyle routine that we stick to.
How can I take control of my gut health? The microbiome is largely shaped by our diet. The Western diet, rich in sugar, highly processed foods and low in fiber has been shown to decrease the diversity of the microbiota and specifically drive down the beneficial strains. Diet rich in whole foods and insoluble fiber are associated with a diverse and robust microbiome. Of course, the complete scientific picture is more nuanced, but this top-level view provides a helpful shortcut.
Other lifestyle choices can help: there are studies demonstrating that daily exercise supports good microbial diversity and strengthens the protective barrier functions of the intestine.
Your social life matters, too: interactions with other humans as well as pets are also effective transmission vectors. Individuals with larger social networks seem to have more diverse gut microbiomes. So going to that yoga class or after-work socializing turns out to be beneficial for your gut flora, too.
What's the take home? Gut microbiota represent a changing ecosystem that is continuously tested by many factors such as unbalanced diet, stress, antibiotic use or disease. The richer and more diverse the microbiota, the higher your resistance to external threats. So, while it is increasingly understood that microbiome diversity is key, we must mention that there is no single, one-size-fits-all recipe for a healthy microbiome, much like there is not a perfect painting. Fortunately, nature has equipped us with a resilient canvas and society is giving us plenty of lifestyle and nutrition choices. So, you decide what your painting will look like!
References
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6351938/