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Cognitive Crossroads: The Importance of the Gut Microbiome

Authored by Rma Lara Polce

Art by Amelia Wildermuth


You know that pit-in-your-stomach feeling, the anxiety you get when you know there is something wrong but cannot tell why; most people treat this as superstition, but what if it is actually scientific? 


For a long time, many people have thought conditions like nausea and abdominal cramps were just the result of signals from the brain to the gut, and while this may be true, the reality is much more intricate [1]. The gut-brain axis (GBA) is a bidirectional system that allows information to flow from your brain to your gut and from your gut to your brain through various pathways, including interactions between the enteric and central nervous system [2]. These systems converge and exchange information in the form of immune activation, intestinal permeability, enteric reflux, and endocrine signaling [2]. Through these interconnections, the GBA has emerged as an extremely sensitive pathway [3]. In fact, your gut is so sensitive to emotion that even the thought of eating initiates the release of digestive fluids [3]. The brain is also equally as sensitive to gut signaling, as it has been shown that patients with irritable bowel syndrome (IBS) typically present with higher rates of mental illness, including depression [4]. IBS treatments targeting the brain, including cognitive behavioral therapy, hypnosis, and mindfulness-based therapies, have been shown to improve the symptoms of IBS, but are not widespread [4]. There is an evident link between our stomach and brain, so why do we keep ignoring it?


Our stomach microbiota, an integral part of our GBA, face a frequent onslaught from our society’s lifestyle choices, from overly accessible McDonald’s drive-throughs to instantly prescribed antibiotics at the first sign of a cold. The recommended fat intake is less than 10% of our daily caloric intake; however, these guidelines are hardly ever adhered to. On average, only 34% of Americans aged 20+ met this recommendation with an average fat intake of 7.4% [5]. Those who failed to meet this threshold had an average of 13.9% fats in their daily intake [5]. Our increasingly high-fat diets have been shown to reduce levels of important gut microbiota including A. muciniphila and Lactobacillus–two bacteria known to aid us in maintaining healthy metabolic states [6]. Without them, we are much more susceptible to infections and a degradation of our stomach barrier [7]. 


Beyond this, every time you consume antibiotics there is always a risk of killing harmless yet integral bacteria since antibiotics don’t specifically target pathogens [8]. This risk is heightened due to an unnecessary use of strong antibiotics, which is becoming more and more prevalent. In fact, each year in the U.S., the Center for Disease Control estimates that 47 million–or 28%–of all prescription antibiotic courses are prescribed unnecessarily for many conditions, including common viruses like the flu [9]. This blatant overuse has been leading to the increased prevalence of antibiotic resistance, loss of microbial diversity, and altered metabolic states in the population [8]. These effects become scarier when you consider the fact that each year in the U.S., more than 2.8 million infections are from antibiotic-resistant bacteria, resulting in 35,000 deaths annually [10]. To heal our GBA, we have to start by evaluating the way we treat our microbiota. 


If you are still unconvinced, let’s dive deeper into the context of the role that our microbiota plays in our well-being. Our gut microbiome is extremely diverse in its composition and function; in fact, there are between 300-500 unique species of bacteria living in your gut as you read this [11]. These microorganisms play a huge role in digestion. For example, Bacteroidetes help us break down complex carbohydrates that we would otherwise be unable to digest [12]. Additionally, Ruminococcaceae, another gut bacterium, produces short-chain fatty acids (SCFAs) by fermenting dietary fiber [13]. SCFAs have been shown to exhibit anti-inflammatory effects as well as metabolic benefits [13]. Not to mention, our microbiota are integral to our immune function since they can train the immune system to recognize pathogens and maintain tolerance to advantageous bacteria [14]. Our microbiota play a crucial role in all facets of bodily function and keeping us healthy, ranging from our gastrointestinal tract to our immune system.


Our microbiota enables us to live healthy lives, yet we continuously place them under strenuous conditions. We truthfully are in an oxymoronic situation, especially given how much time and energy we dedicate to studying them. In the last decade, major countries including France, Canada, and China have collectively spent over 1.7 billion dollars on microbiome research, yet we have seen no significant change in lifestyles, treatments, or our products [15]. This ultimately raises the question: With new evolving GBA technology each day, how can we be excited about these efforts if we refuse to take the required steps to properly maintain our microbiome and with that our mental health? 



References 

[1] The gut-brain connection. (2020, May 21). Harvard Health. https://www.health.harvard.edu/diseases-and-conditions/the-gut-brain-connection

[2] Carabotti, M., Scirocco, A., Maselli, M. A., & Severi, C. (2015). The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems. Annals of gastroenterology, 28(2), 203–209.

[3] Forum, F., Board, F. and N., & Medicine, I. of. (2015). Interaction between the brain and the digestive system. In Relationships Among the Brain, the Digestive System, and Eating Behavior: Workshop Summary. National Academies Press (US). https://www.ncbi.nlm.nih.gov/books/NBK279994/

[4] Ballou, S., & Keefer, L. (2017). Psychological Interventions for Irritable Bowel Syndrome and Inflammatory Bowel Diseases. Clinical and translational gastroenterology, 8(1), e214. https://doi.org/10.1038/ctg.2016.69

[5] Bowman, S. A., & Clemens, J. C. (2010). Saturated fat and food intakes of adults: What we eat in america, nhanes 2017-2018. In FSRG Dietary Data Briefs. United States Department of Agriculture (USDA). http://www.ncbi.nlm.nih.gov/books/NBK588575/

[6] Singh, R. K., Chang, H. W., Yan, D., Lee, K. M., Ucmak, D., Wong, K., Abrouk, M., Farahnik, B., Nakamura, M., Zhu, T. H., Bhutani, T., & Liao, W. (2017). Influence of diet on the gut microbiome and implications for human health. Journal of translational medicine, 15(1), 73. https://doi.org/10.1186/s12967-017-1175-y

[7] Guo, M., Lu, M., Chen, K., Xu, R., Xia, Y., Liu, X., Liu, Z., & Liu, Q. (n.d.). Akkermansia muciniphila and Lactobacillus plantarum ameliorate systemic lupus erythematosus by possibly regulating immune response and remodeling gut microbiota. mSphere, 8(4), e00070-23. https://doi.org/10.1128/msphere.00070-23

[8] Ramirez, J., Guarner, F., Bustos Fernandez, L., Maruy, A., Sdepanian, V. L., & Cohen, H. (2020). Antibiotics as Major Disruptors of Gut Microbiota. Frontiers in cellular and infection microbiology, 10, 572912. https://doi.org/10.3389/fcimb.2020.572912

[9] CDC. (2023, February 10). What’s the big deal about antimicrobial resistance? Centers for Disease Control and Prevention. https://www.cdc.gov/antibiotic-use/antibiotic-resistance.html

[10]Antibiotics: Are you misusing them? (n.d.). Mayo Clinic. Retrieved October 6, 2023, from https://www.mayoclinic.org/healthy-lifestyle/consumer-health/in-depth/antibiotics/art-20045720

[11] Quigley, E. M. M. (2013). Gut bacteria in health and disease. Gastroenterology & Hepatology, 9(9), 560–569. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3983973/

[12] Sonnenburg, E. D., & Sonnenburg, J. L. (2014). Starving our microbial self: the deleterious consequences of a diet deficient in microbiota-accessible carbohydrates. Cell metabolism, 20(5), 779–786. https://doi.org/10.1016/j.cmet.2014.07.003

[13] Ríos-Covián, D., Ruas-Madiedo, P., Margolles, A., Gueimonde, M., de Los Reyes-Gavilán, C. G., & Salazar, N. (2016). Intestinal Short Chain Fatty Acids and their Link with Diet and Human Health. Frontiers in microbiology, 7, 185. https://doi.org/10.3389/fmicb.2016.00185

[14] Belkaid, Y., & Harrison, O. J. (2017). Homeostatic Immunity and the Microbiota. Immunity, 46(4), 562–576. https://doi.org/10.1016/j.immuni.2017.04.008

[15] Danyi Li, Chunhui Gao, Faming Zhang, Ruifu Yang, Canhui Lan, Yonghui Ma, Jun Wang, Seven facts and five initiatives for gut microbiome research, Protein & Cell, Volume 11, Issue 6, June 2020, Pages 391–400, https://doi.org/10.1007/s13238-020-00697-8

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