Have you ever felt butterflies in your stomach? Emotions are connected to our gut, as well as the brain function. This is known as the gut-brain axis.
Your brain affects your gut health, and vice versa. In between these two points, we have the gut microbiota, which largely affects the gut-brain axis.
In this psot, we review the impact of the gut microbiota in the gut-brain axis!
What’s the Gut Microbiota?
These microorganisms have established, through evolution, a symbiotic relationship with the host (humans). While you give them a place to live, they benefit you by supporting your intestinal development and maturation (source)
Everyone of us shows a different gut microbiota, making it part of our identity. If we had the tools to identify 100% the gut microbiota, we could use it as our biological ID (no more ID cards or passports).
The gut microbiota is developed during the first years of life (source). After that, your lifestyle (diet, physical exercise, stress, family life,...) will shape the gut microbiota along your lifespan.
Health Benefits of the Gut Microbiota
We have ten times more bacterial cells than human cells... imaging how much these microorganisms can impact your health.
The gut microbiota has a big word in your health. Although research is still in progress, we know a bit of how the gut microbiota can benefit you!
There are four main functions the gut microbiota shows to improve:
Metabolic Function: The gut microbiota can help your digestion and convert them in nutrients you can use to produce energy (source)
Inmunity: The intestinal barrier is the first main defense we have in our body. The gut microbiota improves permeability of the intestinal barrier (source). It also interacts and boosts the inmune system (source).
Prevent Diseases: The 'good' bacteria prevents from the 'bad' bacteria to colonize our gut. This lowers the risk of diseases, and improves your overall health.
Brain Function: The connection between the brain and gut is interfered by the gut microbiota. But more about this in the next 5min... Scroll down!!
Introduction to the Gut-Brain Axis
Have you ever felt butterflies in your stomach? Have you felt stomach pain when you were going through tough moments?
The interaction between the gut and brain is quite obvious. The communication system between your gut and brain is called the gut-brain axis. Your brain affects your gut health and your gut may even affect your brain health (source)
You've seen the impact of the gut microbiota in your gut health. Adding this to the gut-brain axis equation, we end up with the microbiota–gut–brain (MGB or BGM) axis (source). This concept refers to the role of the gut microbiota in the biochemical signaliging event between the central nervous system and gastrointestinal tract
Scientific Definition - Gut-Brain Axis
The gut-brain axis (GBA) consists of bidirectional communication between the central and the enteric nervous system, linking emotional and cognitive centers of the brain with peripheral intestinal functions (source)
The gut as your 'second brain'
A lot of people consider the gut the 'second brain' (source). There's an interplay between the brain and the gut. Keeping your gut healthy can, then, improve your brain function (and vice versa)
The digestive tract contains 500 million neurons. These are connected to your brain through the nervous system (source)
The enteric nervous system is independent of the central nervous system. It includes neural circuits responsible of motor functions and other related tasks.
The vagus nerve connects the gut and brain. It sends biochemical signals in both directions (source). It acts as the highway between both structures.
The Gut-Brain Communication
The gut and brain are strongly connected. The connection is such, that your brain is able to 'sense' the environment in your gut, as well as you gut modulates depending on your 'brain status'.
The mechanisms proposed for the communication between the gut and brain rely on 5 different pathways:
Vagus Nerve: as one of the main neural channels, the vagus nerve creates a two-ways highway between both organs (study)
Metabolites: the gut microbiota, present in our gut, produce a series of metabolites that cross the blood-brain barrier and interact with the brain (study)
Inflammation: the gut microbiota is a good modulator of inmunity and inflammation (study). The brain is highly susceptible to these two. Therefore, it's regulated by the gut microbiota.
Enteric Nervous System: the enteric nervous system is independent of the central nervous system. It's able to drive electrical signals throughour the digestive system and give feedback to the central nervous system. From there, it'll reach the brain.
Neurotransmitters: a big part of the neurotransmitters are produced in our gut (study). Almost 95% of serotonin is produced by the gut microbiota, but other molecules such as dopamine or GABA are also produced there (study)
The Gut Microbiome and the Gut-Brain Axis
The gut microbiome has a lot to say in the gut-brain axis. In fact, some people refers to the microbiota-gut-brain axis (MGB). As part of your enteric system, the gut microbiota can affect your mood, prevent brain disorders, or even improve your cognitive function.
Gut Microbiota can Improve your Mood
Due to the link between the enteric and central nervous system (study), it's not crazy to think there's a relation between our gut health and our mood.
These findings started back in 1998, when rats fed with Campylobacter led to anxiety-like behaviour (study). From there, germ-free animal experiments and human studies have evdienced the impact of the gut microbiota in your mood.
Microorganisms in your gut produce metabolites called short chain fatty acids (SCFAs). These compounds are able to cross the blood-brain barrier, acting as decisive humoral influencers (study).
There are other mechanisms proposed to understand the MGB connection. The contribution of the gut microbiota in inflammation, inmunity, intestine permeability, production of bioactive peptides,... may affect your mood and brain function as well (study)
Mental Disorders and the Gut-Brain Axis
There's growing evidence on the gut-brain axis role on mental health and prevention of mental disorders.
The effect of the gut-brain axis on preventing mental disorders has been largely studied. Different strains seem to have different roles on the development of different mental disorders.
Through resarch, we are now able to identify the major responsible microorganism species for the main mental disorders. To date, we know that the gut microbiota and gut-brain axis may improve the status of MDD, BPAD, anxiety, psychosis, and neurodegenerative disorders (study)
The Gut-Brain Axis on the Brain Function
The intestinal microbiota is able to produce many neurotransmitters such as dopamine, serotonin, norepinephrine, and δ-amino butyric acids (GABA) that also exercise their own effects on the brain (source)
Due to the strong connection between gut and brain, your brain is able to 'sense' the environment in the gut. Specific microorganisms have been identified as major responsibles of learning and working memory (study), or neurodevelopment (study)