Image showing the relationship between the Brain and the Gut

10 min read

The Gut-Brain Axis: How Your Microbiome and Mental Health are Linked

The human body has more bacteria than cells. And collectively, the different species and types of bacteria are referred to as the microbiome or gut microbiota. Those trillions of bacteria living in your gastrointestinal system impact multiple systems, organs, and processes in our body and impact our overall health and well-being. Similar to how different types of medications work differently, bacteria do too, and a balance between the different types, and ‘good’ and ‘bad’ is needed.


What is the Gut-Brain Axis?


The gut-brain axis describes how the gut and the brain interact and talk to and influence each other. That is why your gut is sometimes called your ‘second brain’ and why we have 'a gut feeling’ or ‘have butterflies’ in anticipation of an event. The connection between the brain, gut, and microbiome has a significant impact on health and is currently an exciting and up-and-coming area of active research.


Gut-Brain Axis and the Microbiome


Mounting evidence indicates that a healthy gastrointestinal tract that has a diversity of microbiota is essential for normal brain function and well-being.1 Scientists are investigating the communication pathway between the brain and the gut to better understand how neurological and neuropsychiatric disorders such as stress, autism, depression as well as Parkinson’s, and Alzheimer’s disease are connected and possibly caused by an imbalance of the gut microbiota.2 Side effects of a fast-paced lifestyle that includes eating highly processed foods, experiencing stress, taking antibiotics, and being exposed to pesticides can all contribute to an imbalance of the gut microbiota.


Pathways of the Gut-Brain Axis


There are several pathways that connect the gut and the brain. Because these two systems are in regular communication treatments and therapies that help one may also help the other.


The Vagus Nerve Pathway


The Vagus nerve is the primary link between the brain and the gut and has an important job communicating and overseeing many body functions including managing mood, immune response, heart rate, and digestion.3 The intestinal microbiota and the chemicals produced regulate nerve signals. The vagus nerve controls gastrointestinal motility—the contractions that move food through the digestive tract through the process of digestion.


With the plethora of bacteria living in the gut, they can impact how the body digests food and create chemicals that aid with hunger and fullness signals that are sent to the brain—so the gut bacteria may influence both weight and appetite.


The Endocrine Pathway


The endocrine system is made of glands that make and regulate hormones and is another communication highway connecting the brain and the gut.4


Endocrine system hormones regulate metabolism, growth, reproduction, sleep, and mood. Stress produces cortisol impacting the endocrine system and can lead to disruptions in mood and digestion. Cutting-edge research is seeking to better understand how the microbiome can keep cortisol levels from increasing to reduce anxiety and help alleviate depressive symptoms.


The Immune Pathway


Most of the immune system (70%) resides in the gut and the bacteria work diligently responding to toxins, foreign invaders, and pathogens. Stress can also impact the immune system in a variety of ways that include thinning the lining of the gut potentially allowing ‘bad bacteria’ or toxins through and activating the immune system. These pathogens can also lead to inflammation and gastrointestinal disorders.


Inflammation, Depression, and the Microbiome


It is believed that an imbalance of the gut microbiota triggers inflammatory processes and also impacts mood.5 It is understood that mental health issues disorders are complex and those with depressive disorders suffer from multiple conditions simultaneously—stress hormones are imbalanced and inflammation that impacts the brain, immune and digestive systems.


Microbiome and Mental Health Takeaway


As we learn more about the role of the gut microbiome and how it impacts health—it is increasingly clear that maintaining a balanced and healthy gut microbiota is essential to overall health and well-being. The gut-brain axis impacts multiple systems that are integral in controlling mood, hormones, and digestive health as well as building a strong immune system.


Sources

  1. Suganya, K., & Koo, B. S. (2020). Gut-Brain Axis: Role of Gut Microbiota on Neurological Disorders and How Probiotics/Prebiotics Beneficially Modulate Microbial and Immune Pathways to Improve Brain Functions. International journal of molecular sciences, 21(20), 7551.
  2. Kim, N., Yun, M., Oh, Y. J., & Choi, H. J. (2018). Mind-altering with the gut: Modulation of the gut-brain axis with probiotics. Journal of microbiology (Seoul, Korea), 56(3), 172–182. https://doi.org/10.1007/s12275-018-8032-4
  3. Breit, S., Kupferberg, A., Rogler, G., & Hasler, G. (2018). Vagus Nerve as Modulator of the Brain-Gut Axis in Psychiatric and Inflammatory Disorders. Frontiers in psychiatry, 9, 44. https://doi.org/10.3389/fpsyt.2018.00044
  4. Neuman, H., Debelius, J. W., Knight, R., & Koren, O. (2015). Microbial endocrinology: the interplay between the microbiota and the endocrine system. FEMS microbiology reviews, 39(4), 509–521. https://doi.org/10.1093/femsre/fuu010
  5. Hayley, S., Audet, M. C., & Anisman, H. (2016). Inflammation and the microbiome: implications for depressive disorders. Current opinion in pharmacology, 29, 42–46. https://doi.org/10.1016/j.coph.2016.06.001
Cheat Sheet
  • The gut-brain axis describes how the gut and the brain interact and talk to and influence each other. That is why your gut is sometimes called your ‘second brain’ and why we have 'a gut feeling’ or ‘have butterflies’ in anticipation of an event.
  • Mounting evidence indicates that a healthy gastrointestinal tract that has a diversity of microbiota is essential for normal brain function and well-being.
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