The Gut-Brain Axis and Microflora

There are many things that I find incredible and truly interesting, but the topic of the gastrointestinal microflora and influence on the gut brain axis is one that really intrigues me.  It is a far reaching subject, having interwoven itself into many health concerns that we contend with on a daily basis.  When it comes to gastrointestinal health, we all have our ups and downs, with obvious digestive concerns on some days, not so much others.  However, I think we truly miss the boat, not only in connections with health concerns that we may have, but also regarding opportunities to intervene and take control for the better.  

Gut Brain Axis and Microflora

Gut Brain Axis and Microflora

I’ve learned over the years that what truly intrigues me, doesn’t always intrigue another, or maybe we find interest in the same subject matter, but on different levels.  This topic is one of those, that many may find interest in, but not to the same level as I, which is fine.  Given this, I try to hone down the material, keeping it focused on the main points of concern.  This is not always easy to do, as I do get consumed with the material and excited to see the connections.  The topic of GI microflora, gut brain axis, and health is a complex but yet, very interesting topic of discussion.  The more research being conducted, the more complex it becomes and the more we are able to make connections.

In a prior article, we discussed the topic of depression, which is a condition that a high percentage of people contend with either themselves or in another on an almost daily basis.  Another condition, which is not far removed, is anxiety or anxiety related disorders.  Moving along this same path, we have others including Alzheimer’s, generalized cognitive disorders and “brain fog“.  The interesting thing to me, as I dig through research, is that despite each condition having it’s own name, many can be tied back to one another, being almost a progression of the prior, and more importantly being linked back to gastrointestinal health.

The Gut Brain Axis

The gut brain axis (GBA) is simply put, a connection between the workings of the mind and the functions of the gastrointestinal tract.  It is bi-directional, meaning that a dysfunction of the mind can impact the functions of the GI tract, but it can also work the opposite way as well.  A dysfunction of the GI tract can hinder or impact normal function of the mind and central nervous system.  In scientific terms, the GBA is bi-directional connection between the central nervous system (CNS) and then enteric nervous system (ENS), being related to the digestive tract.  It is linking the impact of emotions and cognition with the functions of the digestive tract.  In reality, we are talking about possible connections between the enteric nervous system (gut), central nervous system, autonomic nervous system and the hypothalamic-pituitary-adrenal axis (HPA).  It is also linking emotional and cognitive function with not just gastrointestinal function, but also immune health, intestinal permeability (leaky gut), GI motility disorders (IBS, IBD) and endocrine gland function. (1) This covers pretty much every action in our body!

We don’t have to read this research to know that this problem or interactions exists.  The gut brain axis is a real thing, in all of us. We’ve all experienced ‘butterflies’ in our stomach or experienced intermittent digestive upset.  If we look back on these events, many times they are directly tied to something we ate, but more times they are connected to a stressful event we were enduring.  Maybe it was an argument, a deadline at work or a presentation we had to make.  These ’emotional’ or stressful events, triggered a reaction in our gut.  It happens, but if we extend it to a daily occurring event on a low level, considering dietary or stressful lifestyles, maybe we can begin to just get a glimpse of what may really be going on health wise.

The Microbiome & Health

The gastrointestinal microbiota is the population of bacteria that is present within the GI tract.  This population can vary from one individual to the next, to certain degrees, and is highly dependent not just on diet, but also other factors such as stress and even disease.  The bacterial populations present within the gut can not only impact digestion and GI function, but extend into the workings of the central nervous system, endocrine function, immune function, inflammation and even metabolic regulation.

A dysbiosis is the term used to describe a GI microflora that is out of balance, creating health concerns for that individual. This can again, be a primary digestive concern, or created secondarily to other health and mental conditions, including stress.  The bottom line is that the microflora within our GI tract can get out of balance, with some populations becoming more dominant while others less so, which can then impact health on many levels.  Cases of IBS, IBD and even cases of brain fog, are primary examples of dysbiosis, but seeing how they are also connected with mood disorders, one can question who came first?  Mood disorder or dysbiosis? Considering that our brain chemistry can influence the microbiota and the other way around, as well.

Everything appears to be connected, without getting to detailed in our discussion.  If our mood is sour, due to a primary event, then this can influence the GI microflora through alterations in the neurochemistry of our body.  Our mind becomes depressed and with this, our GI tract can become depressed or sluggish or even accelerated.  As we slow down or speed up motility, within our gut, then this can theoretically also impact bacterial populations and their growth rates.  Include into this the impact of diet and influence of stress, we can quickly double the problem.

The microflora is not just involved in digestion, but through the beneficial metabolites produced which include short chain fatty acids; butyric acid, propionic acid and acetic acid.  These metabolites can then influence the nervous system, brain neurochemistry and even memory and learning.(1)

Probiotics and the Microbiome

Prebiotics, probiotics and antibiotics have all been researched and demonstrated interesting results, not just on gut health, but on mood and overall well being.  Antibiotics are often used in cases of small intestinal bacterial overgrowth (SIBO), which can help to eliminate negative bacterial overgrowths, but also may impact the perceived ‘good’ bacteria as well.  Prebiotics are also helpful in many, as they can help to promote the growth of the ‘good’ bacteria by providing necessary substrates, including fiber, which is one reason why science promotes a healthy diet. Probiotics are a growing field and one of interest, working together potentially with prebiotics and diet modifications.  Many probiotics have been investigated, but two tend to stand out in human medicine; Lactobacillus and Bifidobacteria species. Both have demonstrated positive gains, but to me, Bifidobacterium species appear to be the ones of interest when it comes to the influence of the microbiome and mental health.  This is not just cognitive disorders, including memory or Alzheimer’s, but also includes generalized depression or anxiety.

In rodent models, treatment with Bifidobacteria longum species restored tight cell junctions (leaky gut), attenuated the HPA stress response and activities of the autonomic nervous system. (1)  In a study of colitis in rodents, supplementation with Bifidobacgteria longum reduced anxiety-like effects while also altering brain chemistry. (2)  When it comes to overall influence on the general microbiome, supplementation with 20 milion CFU’s of Bifidobacteria longuum BB536, resulted in moderate increases in short chain fatty acid production, reduction of putrefactive substances, but also appeared to alter the entire microbiome through increases of Bifidobacteria, Lactobacillus and also reduction in potentially harmful species, including Clostridium. (3) In another article, we discussed probiotics in more depth.

Summing Up Brain Gut Axis and Influence of the Microflora

In the end, unlike the catch line for Las Vegas, what happens in the gut doesn’t stay in the gut.  The effects are far reaching.  The gut is not just a primary contributor to our health, through diet and stress interactions, but is also a secondary bystander, being influenced by our mind and emotions.  This is the gut brain axis which can influence digestion and overall health. The bottom line impact appears to be localized to changes in the bacterial populations or microbiome, which then influences our health on many levels including mood and cognitive function.  The good news is that science shows us that there are opportunities to intervene and potentially, we are in more control than what we originally thought. There are many opportunities to intervene, the question is what choice do you make?


Author:  Tom Schell, D.V.M., CVCH, CHN



  1. Carabotti, M et al. The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems. Annals of Gastro. 2015. 28, 203-9
  2. Bercik, P et al. The anxiolytic effect of Bifidobacterium longum NCC3001 involves vagal pathways for gut-brain communication. Neurogastro Motil. 2011. Dec 23(12): 1132-39
  3. Ogata, T. et al. Effects of Bifidobacteria longum BB536 yogurt administration on the intestinal environment in healthy adults. Micro Ecol Health. 1999. 11:41-46


(Visited 581 times, 1 visits today)

1 comment on “The Gut-Brain Axis and Microflora”

Leave A Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.