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The Gut Brain Connection: Dysbiosis and the Traumatized Brain


Stress, as we have previously seen, effects all the body’s functionality, especially when stress is toxic and/or chronic in nature. The delicate balance of bacteria that lives in the gut is no exception to this imbalance.

Chronic toxic stress, during the[BS1] prime development period of childhood, can have a profound and lasting impact on the gut microbiome, which can contribute greatly to metal disorders in adulthood, including depression, anxiety, and C/PTSD.

The human microbiome, made up of bacteria living in and on the human body, contains roughly ten bacterial cells for every one human cell. Put another way, about 1-3% of our entire body mass is made up of bacteria (for me, that is up to a whopping 4 lbs.!). More and more studies are discovering that the type and location of these bacteria is intrinsically linked with the health of the human host. Mental health is not spared from this phenomenon, and recent evidence strongly points to a link between mental disorders and gut dysbiosis.[1] Not only does evidence suggest this link, but there are further studies that are starting to show that the main stress response system (the HPA axis talked about in depth in a previous article) is intricately linked to the gut and vis versa. [2] Stress can directly effect the bacteria in our gut, pushing it to an altered state, which can increase our stress. A vicious loop to be sure.


Early childhood trauma, which is considered prolonged toxic stress, causes an increase in overall inflammation in the body1 (a topic I will cover in more depth in a later article). I bring it up here however, because the release of pro-inflammatory cytokines, such as interleukin 6 (IL6) and tumor necrotic factor alpha (TNF-alpha), causes an increase in intestinal permeability and alters the profile of the bacteria living in the gut.[3] LPS and other compounds produced by gut bacteria, coupled with that increased intestinal permeability, activate immune cells to produce even more pro-inflammatory cytokines (IL-6, TNF-alpha, IL-1beta). This becomes a vicious cycle, where the inflammation increases the dis-ease of the gut, and the unhealthy bacteria in the gut increase the inflammation.


Dysbiosis increases the inflammation in the brain, due to commensal bacteria in the gut producing a variety of short chain fatty acids (SFA), which help to maintain the blood brain barrier (BBB). When the gut microbiota is altered, these SFA are less abundant, causing the BBB to be more permeable to substances; substances that would normally be kept out of the brain or the levels of which would be tightly controlled.[4] This permeation of the BBB allows an increase of the pro-inflammatory cytokines to cross and induce inflammation in the brain.4 Increased inflammation produces a change in neurological function, seen as alterations in mood and behavior, resulting in diagnosable mental disorders such as depression, anxiety or C/PTSD.[5] As such, there is a clear link between childhood toxic stress, altered gut microbiome, and altered brain function, all of which collude to produce mental and physical disturbances in the adult person.


Most people have heard mental disorders such as depression or anxiety, are caused by a lack of specific neurotransmitters in the brain like serotonin or dopamine. While that is partially true for many people, taking drugs designed to increase these neurotransmitters’ activity does little to help the symptoms associated with these disorders, and in some cases worsening. Not to mention these types of drugs come with heavy side effects and they must be weaned off of because of their impact on brain function. What is often not mentioned, is the role the microbiome has in production of certain key neurotransmitters/neuromodulators, and/or brain derived neurotropic factors (BDNF= brain builders), and their effect on brain function and health.[6] For example, more than 95% of the serotonin in a person’s body is produced in the gut, and the bacterial composition plays a factor in that production. 2 There is a link that is becoming more and more clear between the health of the gut, and the production/use of key behavioral neurotransmitters such as serotonin or GABA, strongly indicating that mental health is, at least in part, influenced by gut health.

The good thing about healing the gut is that the cells that line the intestines are replaced every 2-5 days. Once you start working to repair this, new healthier cells will be formed rather quickly. Specific diets, such as the GAPs diet or SC diet are good ways to start to heal the gut. Gut healing focuses on 5 specific components; Remove the stressors and gut irritants; Replace nutrients and digestive enzymes as needed; Reinoculate the gut with healthy bacteria through the use of probiotics, prebiotics, and fermented foods; Repair the gut lining (no more leaks!); Rebalance your life, to maintain new healthy gut habits. All of these a nutritional therapist can help put into place in people’s lives.


In summary, to aid in helping adults suffering from the effects of toxic traumatic stress in childhood, mental treatments should not be the only avenue of healing. The evidence clearly points towards a connection between stress and an altered gut biome. Communication between the gut and brain, specifically the main stress response system the HPA axis, is altered as a result. Nutritional protocols are the best way to repair damage done by stress, to the sensitive environment of the gut. Heal the gut, and you can help heal the mind.


References

[1]Leclercq S, Forsythe P, Bienenstock J. Posttraumatic Stress Disorder: Does the Gut Microbiome Hold the Key?. Can J Psychiatry. 2016;61(4):204-213. [2] Cryan JF, O'Riordan KJ, Cowan CSM, et al. The Microbiota-Gut-Brain Axis. Physiol Rev. 2019;99(4):1877-2013. [3] Bonaz B, Bazin T, Pellissier S. The Vagus Nerve at the Interface of the Microbiota-Gut-Brain Axis. Front Neurosci. 2018;12:49. Published 2018 Feb 7. [4] Mohajeri MH, Brummer RJM, Rastall RA, et al. The role of the microbiome for human health: from basic science to clinical applications. Eur J Nutr. 2018;57(Suppl 1):1-14. [5] Karakula-Juchnowicz H, Rog J, Juchnowicz D, et al. The study evaluating the effect of probiotic supplementation on the mental status, inflammation, and intestinal barrier in major depressive disorder patients using gluten-free or gluten-containing diet (SANGUT study): a 12-week, randomized, double-blind, and placebo-controlled clinical study protocol. Nutr J. 2019;18(1):50. Published 2019 Aug 31. [6]Martin CR, Mayer EA. Gut-Brain Axis and Behavior. Nestle Nutr Inst Workshop Ser. 2017;88:45-53.

[BS1]You just used ‘especially right above”

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