Introduction: You’re Not Just Human

Not to make you paranoid, but scientifically speaking, your “gut-feelings” may not be solely of human origin! Rather, they may be mediated by the microorganisms that are inhabiting your gastrointestinal (GI) tract just as much, if not more, than your brain.

It may sound creepy, but it’s true!

In case you haven’t heard, we are host to trillions of tiny microbes (microbiota) inside and outside our bodies. In fact, our GI tract alone is home to 10¹⁴ cells of thousands of different species of microbiota. These critters began moving-in to inhabit us very early in life and they have been found to influence our physical and emotional health in many important ways.

Astonishingly, these bugs in our bellies literally have a brain of their own and are in a two-way communication with our head brain. This bi-directional connection between the enteric (gut) nervous system and the central nervous system is termed the “gut-brain axis.”

In this article, I’m going to highlight key points everyone should know about the gut-brain axis. This will assist in better understanding and treatment of emotional, mental, and neurological imbalances.

It is based on my recent review article on this topic published on Rupa health.

Where Do Gut Feelings Come From?

Over the past few decades, an explosion of evidence has emerged on how our microbiome (the sum of all the genetic information in our microbiota) has incredible power over our mind and body. Doctors and scientists were amazed when it was discovered that a population of microbes in our GI tract not only produced the majority of the body’s serotonin, but also various other metabolites and neurotransmitters. These signaling chemicals impact our cognitive health and interplay with our brain and nervous system in complex ways through multiple pathways.

The scientific findings on the gut-brain connection have had immense implications on how we view mental health and are shifting our viewpoint on the origin and treatment of psychiatric illness. Specifically, we now have evidence that there exists a biological and physiological basis for psychological, neurological, age-related, and neurodegenerative disorders that is rooted in the gut.

Understanding The Gut-Brain Connection

In my article on Rupa Health, I review in more detail exactly how our gut and brain are connected.

Topics include:

A. How our Gut and Brain Communicate

Our gut and brain message each other via several routes.

These include:

1. the immune system (our gut houses over 70% our immune system which has an impact on our brain and neurological processes)
2. tryptophan metabolism (the precursor to the “feel-good” neurotransmitter, serotonin)
3. the vagus nerve (a nerve extending from our brain and into our GI tract. It is akin to a gut-brain “highway” that “transports” communication via signaling molecules.)
4. the enteric nervous system (the neurons and supporting cells of the gut that influence systemic processes)
5. metabolites of microbes that act as signaling molecules and effect health outcomes, such as short-chain fatty acids (SCFAs), branched-chain amino acids, and peptidoglycans (components of the bacterial cell wall)

B. Gut Bacteria and Neurotransmitter Production

Our gut bacteria and brain both produce and react to the same neurochemicals. These include:

1. GABA
2. serotonin
3. norepinephrine
4. dopamine
5. acetylcholine
6. melatonin (a byproduct of serotonin)

These all play a role in mood and cognition. The article provides an overview of the actions of these different neurotransmitters and neurohormones and which gut bacteria produce them.

C. How Gut Inflammation Impacts Mood

Below is an excerpt from my article on Rupa Health on the mechanisms of inflammation and how this impacts our brain:

Various factors such as psychosocial stress, diet, inflammatory adipose tissue, a leaky gut, and an imbalance between regulatory and pro-inflammatory T cells can all contribute to inflammation in the brain. This low-grade chronic neuroinflammation is believed to play a crucial role in forming a basis for the interaction between psychological stress, impaired gut microbiota, and major depressive disorder. (22-23)

Microbes can produce metabolites that enter circulation, alter the inflammatory tone in the gut, periphery, and central nervous system (CNS), and signal the trafficking of immune cells into the brain. Furthermore, the vagus nerve has been shown to modulate brain immune responses.

The good news is that there are means of addressing this. (Note: adipose tissue that is inflamed can be modulated, regardless of body size.)

D. Functional Medicine Lab Tests to Consider When Focusing on the Gut-Brain Axis

Functional medicine lab tests a doctor may consider include:

1. comprehensive stool test
2. neurotransmitter analysis
3. micronutrients
4. omega-3 index (research links fatty acids to not only brain health, but also inflammation and microbiota diversity)

E. 3 Types of Food That Help Increase Mood

1. foods high in b vitamins (these are neurotransmitter precursors)
2. foods rich in magnesium (this is also a neurotransmitter precursor)
3. foods for feeding the microbiome (fermented foods and high polyphenol-containing foods, polyphenols are beneficial plant compounds digested by gut bugs)

F. Herbs & Supplements That Help the Gut-Brain Axis

1. probiotics
2. herbs (ashwagandha, St. John’s Wort, Rhodiola, and saffron)
3. supplements (neurotransmitter precursors and fatty acids)

G. Lifestyle Changes That Help the Gut-Brain Axis

1. exercise
2. sleep
3. stress reduction

Summary on the Gut-Brain

Our moods are not just stemming from our brains. We literally have “gut feelings” that are not human-oriented but rather microbial-based. Bi-directional communication from our gut to the brain occurs through various pathways, including how microorganisms produce and assimilate neuroactive compounds, modulate inflammation, and interplay with the vagus nerve.

Integrative medical practitioners can now work with conventional mental healthcare to ensure that the biological and neurological support of the gut-brain is addressed to improve efficacy in treatment. This can be done through diet, nutrients, herbal approaches, and lifestyle.

Conclusion on the Gut-Brain and Mental Health

Not only will understanding that our gut influences mental health impact treatment for psychiatric and neurological disorders, but it can also decrease stigma.

We need to address all brain health factors and support the gut when treating any mood or nervous system issue.

Click here to get the details and learn more about how our belly bugs influence our brain and vice versa.

References

https://pubmed.ncbi.nlm.nih.gov/31260640/

https://www.tandfonline.com/doi/abs/10.1080/14737175.2019.1638763

https://www.livescience.com/the-gut-brain-axis

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8234057/

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6477058/

https://www.sciencedirect.com/topics/neuroscience/enteric-nervous-system

https://www.rupahealth.com/post/a-functional-medicine-approach-to-understanding-neurotransmitters-101

https://pubmed.ncbi.nlm.nih.gov/21918508/

https://pubmed.ncbi.nlm.nih.gov/31587531/

https://pubmed.ncbi.nlm.nih.gov/35462279/

See full reference list in the original article.

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If you are struggling with mental health issues, please seek professional help: National Mental Health Hotline

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