The Human Microbiome is the collection of all the microorganisms living in association with the human body. These communities consist of a variety of microorganisms including eukaryotes, archaea, bacteria and viruses.
– NIH Human Microbiome Project
Or, more specifically, the microbiome refers to the collective genome of all the microbiota in/on the human body. And there are a lot of them. I don’t want to alarm you, but you have about 10 times more microbial cells living within you than human cells. These microbes live in all sorts of nooks and crannies in your body: your skin, mouth, nose, ears, vagina and especially your gut. But don’t worry, although some of these microbes are total free loaders, and some can cause various health issues (we will get into that later in this 4-part microbiome 101 series), many of our resident microbes actually play an integral role in human health and wellness.
What do our resident microbes do for us?
So. Many. Things. What follows is not an exhaustive list, but a brief overview of the myriad ways in which the microbes living within us play an integral in our health (and even our happiness!), so you can get an idea of just how important these little cohabitants are for humans.
Aid in digestion
Diversity is essential here. Different bacteria have different roles to play in digestion, so you want healthy microbial diversity in your gut. Bacteria help digest macronutrients, including certain fibers that we are unable to digest. Very importantly, bacteria create short chain fatty acids (SCFA) from the fermentation of fiber. SCFAs, which include butyrate, acetate and propionate, have anti-inflammatory properties and are essential for supporting gut health.
Help metabolize drugs
The composition of your microbiota can determine how much of certain drugs will reach the bloodstream (so fascinating, right?!). This means that your microbiota can actually affect the efficacy and toxicity of certain pharmaceuticals, which has huge potential future research implications for people who tend to react poorly to certain medications, or to guide dosing. Not only pharmaceuticals, but the microbes in our gut are essential in the mechanism of how some herbs have an impact on our health. In some studies, a herb that shows poor absorption still has a health effect, and in those cases sometimes that is due to the interaction between the herb and the microbiota.
Produce vitamins and amino acids
Some of our friendly resident bacteria produce vitamin K, which is necessary for blood clotting, as well as some B vitamins, which are cofactors in a whole host of enzymatic process in the human body. They also produce amino acids, which are the building blocks for proteins and are required to make hormones and neurotransmitters.
Create healthy vaginal pH
The vagina has a whole beautiful microbiome of its own. Having a healthy vaginal microbiome, which is predominantly made up of lactobacillus genus, keeps the vaginal pH acidic. An acidic vaginal ecosystem helps to maintain homeostasis and health in the vagina. This acidic environment helps to protect against overgrowth of microorganisms that can cause infections such as candida and bacterial vaginosis (BV). I have worked with numerous women who are stuck in a frustrating cycle of alternating vaginal candidaisis and bacterial vaginosis. That cycle often occurs because the anti-fungal and antibacterial treatments, while effective at killing things off, do not address the root cause, which is often an imbalanced vaginal microbiome and ecosystem.
Part of our immune system
Certain microbes interact with and directly influence our immune system and some of them even secrete antibiotics towards other bacteria. Furthermore, the SCFA butyrate made by our resident friendly microbes plays an important role in differentiation and induction of a number of the cells in our immune system, including T-cells and macrophages. Additionally, our friendly resident microbes help to “crowd out” pathogenic microbes by competing with them for attachment sites and nutrients. Dr. Martin Blaser in his book “Missing Microbes,” goes so far as to say that the microbiome is the “third arm” of the immune system (the first arm being innate immunity and the second arm adaptive immunity).
Support mood
The brain-gut-microbiome axis goes both ways: our microbiome affects our nervous system/brain and vice versa. As far as the microbes’ role goes, they play in the production of neurotransmitters, including serotonin, dopamine and GABA. In fact, the vast majority of serotonin in your body is made in the gut via enterochromaffin cells, with which your microbiome is constantly communicating. Microbes can also affect our mood via the vagus nerve, as well as via their effect on the endocrine system. All these reasons are why, whenever I am working with someone who has any mental health concerns, I am always going to address gut health.
Play a role in hormone balance
The microbes in your gut have an impact on the HPA-axis (hypothyalamus-pituitary-adrenal) axis, which modulates your body’s response to stress. Microbes are also responsible for a percentage of the conversion of thyroid hormone from T4 to T3 and a healthy microbiota is necessary to eliminate estrogen from the body via stool (conjugated estrogen is eliminated via stool, but an imbalanced microbiota cause estrogen to become unconjugated, therefore re-absorbed into the body).
Modulate inflammation
The gut microbiome impacts levels of inflammation not only inside the gastrointestinal tract, but also in the rest of the body. Certain “unfriendly” bacteria produce compounds that are inflammatory and trigger further inflammatory cascades in our bodies. Dysbiosis refers to an imbalanced/unhealthy microbiome, and often is associated with higher levels of chronic inflammation. While it is normal for our bodies to have acute periods of inflammation (ex. when fighting off a virus), chronic inflammation is harmful and drives nearly every chronic disease. Therefore, when working to heal any chronic disease it is essential to address the health of the microbiome.
In part 2 of Microbiome 101 I’ll discuss what factors shape your unique microbiome. To have it sent directly to your inbox, you can sign up for my mailing list, below!