Microbiome 101: What's the Deal?

The microbiome is a collection of trillions of microbes (bacteria, viruses, fungi, and other microscopic bugs) that live in, on, and around us. These bugs are often cited to outnumber us 10:1, meaning 10 bugs to each 1 of our human cells. Hardly seems possible, but remember they are much tinier than our cells, so we’ll give it to them. In a nutshell, our microbiome is an extension of us in a very real way. It serves as a link between many of our internal organ systems and is the primary mode of communication between our inner world and the environment. We wouldn’t be as human as we are without them, they complete us!

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A note because I’m a stickler for definitions: Microbiota refers to all of the microbes of a particular body system as a collective. Microbiome technically refers to the genes of the microbiota, but we use them interchangeably. There’s a microbiota/biome associated with the skin, lungs, mouth, and vagina. Any part of your body that meets the outside world has a microbiome, even the eyes! This article focuses on the microbiome of the gut, which is indeed outside our body.  I love this fun reminder from my colleague Dr. Mark Iwanicki that this is due to our donut design.

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So what does it do?

The gut micobiome has its hands everywhere, impacting nearly every system of the body.  The overarching theme is that it’s a two way street in each system.  It impacts and is impacted by everything, so sensitive!  Much like Dawson, you don't want to upset it. 

For a healthy digestive system:

The gut microbiome helps us to breakdown and absorb our food, ensuring we squeeze every last bit of energy and nutrition from it. Sometimes we can’t get essential vitamins simply from our food, so it makes them from scratch for us. (1) It is also a key player in dealing with dietary fats.  Bile acids (that gross stuff you never vomited in high school after drinking too much) are bounced back and forth between the gut microbiome and the liver. Along the way they expertly handle cholesterol and other fats, keeping what we need and eliminating the rest. Don’t give the microbiome too much applause though, because truth be known it’s responsible for all of our farts. 

For a healthy neuroendocrine system: 

Neurotransmitters and hormones are the molecules that make us act and feel like humans, giving us sensations and emotions and regulating our most fundamental bodily functions. The hormone serotonin, often called the “happiness hormone” is estimated to be 90% produced and regulated by our gut microbiome. But serotonin does far more than regulate our mood. It supports gut function, our immune system, and even our bones. (2) Not to mention it’s a precursor for the “sleep hormone” melatonin, giving our guts direct impact on the quality of our sleep. You guys know from experience that psychological stress effects your digestive function. So you won’t be surprised to learn that your nervous system and your gut are linked in a myriad of ways. We’ll get into plenty of that later, but for now, know that your gut bacteria are absolutely central to the function of your nervous system and the way you respond to the world. (3)

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And we haven’t even gotten to the good parts yet …

For a healthy immune system:

A large portion of your immune system resides in your gut (Gut-Associated Lymphoid Tissue), and it is a bustling site for training on who’s a friend and who’s a foe.  The microbiome informs your immune system how it should respond to different pathogens it encounters, and serves as a regulator of sorts. (4) When your body accidentally mistakes your own cells for the enemy (as in autoimmunity), a healthy gut microbiome will step in on your behalf, and signal to the immune system to take it down a notch. (5) Isn’t it funny that we thought the immune system was there to control bacteria, when it appears the bacteria do a good bit of controlling our immune system? Nature has a good sense of humor.

Epigenetic functions:

I saved the best for last. Have you ever heard that complex diseases like cancer and autoimmune disease are caused by a combination of genetics and environmental triggers? Personally, I was always disappointed in that answer because it’s incomplete. How exactly does the environment wake up which genes? It’s a stretch, and we may never know completely, but the microbiome is revealing itself as a key player. (6) The metabolic byproducts of the microbiome (anywhere, not just the gut) can directly influence the expression of our DNA. How wild is that? But now that we’re onto it, it makes sense, right? On our bodies the microbiome always exists at the interface between our inner world and our outer world, our genes and our environment.

We’ve sufficiently scratched the surface, and I hope you enjoyed it! We’ve so much to talk about in the future. Please leave a comment with your questions or suggestions for future topics below