The human microbiome refers to the ecosystem of microorganisms that reside in and on our bodies. These bugs- bacteria, fungi, parasites, viruses- live with us in a symbiotic relationship, meaning that we need them to survive just as much as they need us. In fact, we have nearly ten times more microbes (most of them bacteria) in our body than we do human cells. (1) The largest of these ecosystems resides within our gut. This gut microbiome is incredibly diverse and highly unique and is greatly linked to our overall immune health.
Our microbiome has the ability to do all of the following:
aid in digestion
protect the body against pathogens
assist in detoxification of toxins found in foods
control the majority of the body’s immune system
modulate inflammatory pathways
The Brain-Gut Connection
Although unknown to most, we depend on our microbiome for survival. An imbalance has been implicated in many chronic disease states. The gut, as a result of the microbiome, is intricately connected with all of the body’s systems, specifically our immune system.
Perhaps the most astonishing is the link between the gut and the brain. The gastrointestinal tract is home to what’s known as the enteric nervous system, which consists of more or less 100 million neurons. (2) While these neurons don’t assist in conscious thinking or decision-making, they allow us to connect with and feel our internal environment. Think about the last time you had to give an important presentation, and you felt sick to your stomach? The brain and the gut communicate with each other in ways that we are only recently starting to understand.
Part of this connection is the influence of our microbiome on the enteric nervous system. The gut produces a very large amount of brain chemicals. It’s thought that up to 95% of serotonin (the feel-good neurotransmitter) in the body is produced in the microbiota. (3) This makes an interesting argument for the role of nutrition as a means for treatment for depression, anxiety, and others.
The Impact of the Microbiome on Mental Health
The primary channel of communication between the gut and the brain is the vagus nerve, which travels from the brainstem to the abdomen. This communication pathway is bidirectional; our microbes are able to send chemical messages up the vagus nerve to communicate with our brain, just as neurons send information down into the gut. Research is now looking into the impact of the microbiome on mental and psychological health. The functions and responsibilities of the gut microbiota begin to breakdown once we start losing biodiversity ( i.e., strains of bacteria, etc.)
Our mental health can directly impact the biodiversity of our microbiome. When we are in a flurry of chronic stress, we overproduce cortisol, which increases the permeability of our gut lining, this contributes to a condition known as leaky gut.
When we are under a normal amount of stress, we create an environment that surpasses Bifidobacteria and Lactobacillus, two healthy strains of gut bacteria.
Alternatively, feelings of fear and anger increase the population of Bacteroides Fragilis; this is a strain of pathogenic bacteria. (4)
Not only does emotional state influence our microbiome, but our microbiome has a direct effect on our psycho-emotional state – This relationship is bidirectional.
Research done on mice showed that by changing the composition of the gut, the mice had a dramatic change in behavior. The same studies have also been done in humans, and the results show the same patterns- changes in the microbiome result in behavior changes and changes in mental state- and these results can and have been measured through tools like functional MRIs. (5)
Keeping Your Gut Healthy
All of the above means that tending to the health of our gut is imperative to achieve optimal health, including our psychological health. We need to keep our microbiota populated with a vast amount of biodiversity.
There are a few ways of keeping our microbiome happy and thriving, but the most influential factor related to gut health and overall microbiome health is nutrition and the food we eat. (6)
