When Everything Goes Wrong: What Gut Dysbiosis Does to the Brain


By: Dr. Shaina Cahill, Ph.D. (Director Medical Communications & Affairs)

When everything goes wrong: the impact of gut dysbiosis on the brain.

We know that a healthy microbiome is essential for overall health and well-being 1–4 (Learn more about the gut microbiome here). Under healthy conditions, the gut microbiome plays a vital role in several processes in the body, including influencing the brain 1,2,5–13 (Learn more about the roles of a healthy gut microbiome here). This communication with the brain happens via the gut-brain axis, a complex bidirectional communication pathway enabling the brain and the gut to communicate 2,14–23 (Learn more about the microbiota-gut-brain axis here).

The importance of the gut-brain axis

Variations and changes in the composition of the gut microbiota influence not only the gut but also normal brain function, and this microbiota-gut-brain communication may contribute to diseases not only in the gut but also in neuropsychiatric-related diseases (including neurodevelopmental and neurodegenerative diseases) 24. Research has shown that the composition of the gut microbiota can influence normal brain functioning and behaviour and contributes to diseases ranging from inflammation to the regulation of anxiety, mood,  and cognition 15,20,24–28.

If an unhealthy gut plays a role in creating an unhealthy brain and contributing to neuropsychiatric-related diseases, it is then possible that targeting the gut microbiota may be a possible new therapeutic approach for complex neurological disorders 24,27,29.

So, what happens when it all goes wrong?

Research over the last decade has indicated a strong association between changes in the gut microbiome leading to gut dysbiosis and many gastrointestinal (GI) and non-GI disorders 2. Many factors have been shown to modulate both the brain and microbiota, including socioeconomic status, host diet, genetics, environmental factors, exercise and level of host activity, medications, and mode of delivery at birth (Learn more about what can cause gut dysfunction here.) 15,30

Figure from Cryan et al., 2019: What can  impact the gut microbiome

It is not surprising that the gut could impact the brain in profound ways, as the research shows the brain depends on gut microbes for many essential products 16. So, dysfunction in the gut microbiome can have serious negative consequences for brain function both from neurologic and mental health perspectives 2,16,31. There is accumulating evidence from both animal and human clinical studies implicating the microbiota-gut-brain axis in a variety of disorders within the central nervous system (CNS) 2,15,29 such as:

  • Neurodegenerative disorders including: multiple sclerosis (MS), Alzheimer’s (AD) and Parkinson’s (PD) diseases 32–49
  • Neuropsychiatric disorders such as: major depressive and mood disorders 50–57,
  • Neurodevelopmental disorders such as: autism spectrum disorder (ASD) 19,58–61

As research around the microbiota-gut-brain axis increases, the number of psychological, neurological and other diseases in which alterations in this axis are implicated continues to grow 15. While the merit of the evidence varies by disease state, there is a need for more randomized clinical trials to understand better the possible causal role the gut microbiome may play in each disease state, and the efficacy of microbial interventions, such as probiotics and FMT protocols, in treating patients 2,15 (Learn about FMT here).

At Novel Biome, we believe in the importance of the gut microbiome for overall health and the possibilities of fecal microbiota transplantation (FMT) to restore gut health and treat disease. Novel Biome focuses on FMT product manufacturing and supplying high-quality products, relying on our world-class donors to allow us to make a significant difference in the lives of many individuals, take our eligibility quiz to see if you can be a stool donor.

References: 1. Belkaid, Y. & Hand, T. W. 2014, 2. Rutsch, A. et al. 2020, 3. Vatanen, T. et al. 2016, 4. Wilson, B. C. et al. 2019, 5. Choi, H. H. & Cho, Y.-S. 2016, 6. Chung, H. et al. 2012, 7.Hansen, N. & Sams, A. 2018, 8. Hooper, L. V. et al. 2012, 9. LeBlanc, J. G. et al. 2017, 10. Rautava, S. & Walker, W. A. 2007, 11. Sassone-Corsi, M. & Raffatellu, M. 2015, 12. Sommer, F. & Bäckhed, F. 2013, 13. Stecher, B. & Hardt, W.D. 2011, 14. Chen, X. et al. 2013, 15. Cryan, J. F. et al. 2019, 16. Dinan, T. G. & Cryan, J. F. 2017, 17. Ding, X. et al. 2020, 18. Jendraszak, M. et al. 2021, 19. Liu, Z. et al. 2021, 20. Rhee, S. H. et al. 2009, 21. Skonieczna-Żydecka, K. et al. 2018, 22. Sudo, N. et al. et al 2004, 23. Wan, Y. et al. 2021, 24. Deidda, G. & Biazzo, M. 2021, 25. Agustí, A. et al. 2018, 26. Carabotti, M. et al. 2015, 27. Cryan, J. F. & Dinan, T. G. 2012, 28. Sarkar, A. et al. 2016, 29. Serra, D. et al. 2019, 30. Bowyer, R. et al. 2019, 31. Cataldi, S. et al. 2022, 32. Bedarf, J. R. et al. 2017, 33. Berer, K. et al. 2017, 34. Biedermann, L. et al. 2013, 35. Friedland, R. P. 2015, 36. Hasegawa, S. et al. 2015, 37. Hill-Burns, E. M. et al. 2017, 38. Houser, M. C. & Tansey, M. G. 2017, 39. Itzhaki, R. F. et al. 2016, 40. Jiang, C. et al. 2017, 41. Keshavarzian, A. et al. 2015, 42. MahmoudianDehkordi, S. et al. 2019, 43. Moos, W. H. et al. 2016, 44. Pisa, D. et al. 2018, 45. Sampson, T. R. et al. 2016, 46. Scheperjans, F. et al. 2015, 47. Unger, M. M. et al.  2016, 48. Zhao, Y. et al. 2015, 49. Clapp, M. et al. 2017, 50. Dinan, T. G. & Cryan, J. F. 2017, 51. Foster, J. A. & McVey Neufeld, K.-A. 2013, 52. Iannone, L. F. et al. 2019, 53. Kelly, J. R. et al. 2015, 54. Luna, R. A. & Foster, J. A. 2015, 55. Valles-Colomer, M. et al. 2019, 56. Zheng, P. et al. 2019, 57. Cenit, M. C. et al. 2017, 58. Hughes, H. K. et al. 2018, 59. Sharon, G. et al. 2019, 60. Tognini, P. 2017.

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