Is there a connection between the Gut & the Brain?

“I have a ‘gut feeling’ this blog is going to be interesting.”

“I had a ‘gut wrenching’ experience at the cafe today”.

We use these terms very commonly in our daily speech, but, ever wondered what sense it really makes? Well, these terms came into being because there is ‘literally’ a gut-brain connection. The gut, i.e., the gastrointestinal tract is responsive to emotional stimuli. Basically, there is a connection between the gut and the brain which makes you ‘feel’ butterflies in your stomach(physical) when you are nervous(psychological). This connection or link is called the Gut-Brain Axis.

What is Gut-Brain Axis (GBA)?

The Gut-Brain Axis is a bidirectional neural processing of information between the brain and the digestive system. The gut–brain axis mainly comprises of the following :

• The central nervous system(CNS)- part of the nervous system consisting of the brain and spinal cord.
• Neuroendocrine system (including hypothalamic–pituitary–adrenal axis) – regulates digestion, immunity, sexuality, emotions & mood, energy, and stress response.
• Neuroimmune systems,
• Autonomic nervous system (ANS)- regulates bodily functions, such as, heart rate , digestion, respiration , urination ,  sexual arousal & fight-or-flight response.
•  Including, Enteric nervous system (governs the functions of gastrointestinal tract),
•  Vagus nerve (cranial nerve related to parasympathetic system of ANS) and,
• Gut microbiota (microorganisms crucial for homeostasis- state of steady internal, physical , and chemical conditions maintained by living organism (Betts, et.al., 2013). https://en.m.wikipedia.org/wiki/Homeostasis.

The gut-brain axis plays an important role in the regulation of gastrointestinal (GI) motility, digestion, secretion, absorption, blood flow, regulation of appetite,  balance, energy and metabolism, etc.

Alterations in Gut Flora

Gut flora:

Gut flora or the gut microbiota, is a complex community of microorganisms that resides in the digestive tracts of humans and other living beings. These include bacteria, fungi, archae, etc. (Saxena, R.; Sharma, V.K, 2016). These organisms collect energy from the food we consume which helps our metabolism. It also plays an important role in the synthesis of necessary vitamins in our body and helps metabolise other endocrine acids. The composition of the gut flora/microbiota changes overtime with changes in diet improvement or deterioration of health. Disruption in the gut microbiota is implicated in several physiological and psychological disorders such as auto-immune disorders, psychosomatic disorders, etc. https://en.m.wikipedia.org/wiki/Gut–brain_axis

Although the gut microbiota is essential in maintaining our health, it can go out of control if the ‘bad bacteria or virus’ enters the system externally. This state of instability, wherein; the gut is not able to restrict growth and replication of the ‘bad bacteria or virus’ is called dysbiosis (Stewart, 2020). When this happens, it causes inflammation in the gut, sending alarms to the immune system of our body. The gut flora can be manipulated or altered by certain drugs or chemicals, both natural or artificial. Two of them are listed below to better understand the researches that follow in this blog.

Antibiotics:

Antibiotics are pharmaceutical drugs that helps to stop infections caused by bacterias. Infections are caused when faulty bacterias, fungus or viruses enter our body via different mediums and start to affect or damage the other cells around it. Therefore, to stop an infection, an antibiotic either kills the bacteria or prevents it from replication. Basically, the changes happen in the gut microbiota, which reduces the symptoms experienced by the individual.

Probiotics:

When you consume antibiotics, the host bacteria and a part of the bacteria which turned bad, is lost as a part of the damage done by the infection. Probiotics, is the ‘good bacteria’ that helps your gut replace the loss. Probiotic bacteria is present in the gut where they spread positive influence on health as a whole, as well as anxiety and stress. The probiotic bacteria encourages the general well-being of a happy gut microbiome. They produce short-chain fatty acids (main source of energy for the cells lining the large intestine) and other substances that nourish the body. Probiotics are also present in supplement form and in a variety of food substances (Stewart, 2020 ). https://atlasbiomed.com/blog/stress-anxiety-depression-microbiome/

Gut-Brain Axis (GBA) & Mental Health Disorders

Psychological factors can lead to changes in the physiology of the gut and vice versa. That is, psychological stress, or mental health disorders, etc. can affect the motility & contractions of the gastrointestinal (GI) tract and conversely, the alterations in gut microbiota can also trigger mental health disorders. This is where psychosomatic disorders and symptoms of somatoform disorders come into picture. Psychosomatic disorders are when an existing medical condition, gets aggravated by psychological conditions. Example: Irritable Bowel Syndrome. Somatoform disorders are when physical symptoms are observed in the individual although there is no underlying medical condition or pathology. Example: Cyclical Vomiting, physical symptoms in conversion disorders, etc.

GBA & Perceived Stress:

Research conducted by Foster. A, Rinaman. L and Cryan. J (2017) showed that the gut microbiota is an important component in control of the gut-brain axis, especially during conditions of stress, provoked by real or perceived homeostatic challenge. Results depicted that alterations in the early microbial composition due to antibiotic exposure, birth by C-section, infection, lack of breastfeeding, exposure to stress & other environmental influences, along with influence of host genetics can result in long-term modulation of stress-related physiology and behavior. The gut microbiota has also been implicated in a variety of stress related disorders such as anxiety, depression & irritable bowel syndrome (Foster, Rinaman, and Cryan, 2017). https://pubmed.ncbi.nlm.nih.gov/29276734/

GBA & Depression:

Mental health disorders are mainly implicated due to changes in the neurotransmitters. Serotonin, is one such neurotransmitter which affects the mood, sleep, sexual desire, memory, etc. Any imbalance in serotonin is implicated in depressive disorders. A study found that serotonin is a key regulator of gastrointestinal motility and secretion. The findings revealed that gut microbiota acting through Short Chain Fatty acids are important determinants of serotonin production & homeostasis (Reigstad, Salmonson, Rainey, et. al., 2015). https://pubmed.ncbi.nlm.nih.gov/25550456/ That is, if there is a glitch in the serotonin production in the gut, it may lead to mental health disorders such as Major Depressive Disorder, obsessive compulsive disorder, anxiety, etc.

GBA & Anxiety:

Another neurotransmitter, Gamma-Aminobutyric Acid (GABA), plays an important role in regulating and improving mood. GABA is produced in the gut and acts as a relaxant by restricting counter- effects of excessive stimulation in the brain. Therefore, GABA helps in controlling the fear and anxiety related symptoms. Researches show that changes in gut microbiota can lead to alterations in the GABA, which can reduce or increase anxiety and depression related symptoms (Robertson, 2020). https://www.healthline.com/nutrition/gut-brain-connection

GBA & gastrointestinal disorders:

Additionally, Irritable Bowel Syndrome (IBS), is a psychosomatic, gastrointestinal disorder which is characterized by unusual bowel movements, intestinal pain & bloating.  Depression and anxiety are usually comorbid with IBS. Genetic and other factors are also present. IBS improves with proper diet, counseling for anxiety or depression and medication (both for physical and physiological symptoms) .

GBA & Schizophrenia:

Clinical findings revealed that patients suffering from schizophrenia have increased level of lactic acid bacteria and other bacteria responsible for adaptive immune responses associated to schizophrenia. To establish a link, they administered probiotics that can alter these bacteria. It was found that probiotics helped in reducing some behavioural symptoms in schizophrenia. According to the study, patients suffering from schizophrenia had several bacteria associated to severity of psychotic symptoms in excess amount in the gut. Thus, alterations in the gut microbiota implicates psychotic symptoms or disorder. (Rege & Graham, 2017). https://psychscenehub.com/psychinsights/the-simplified-guide-to-the-gut-brain-axis/

GBA & Autism Spectrum Disorders (ASD) :

ASD is a neurodevelopmental disorder which is caused both due to genetic defects and faulty environmental patterns. Researchers attempted to study genetics of children suffering from ASD through feacal matter and found that certain bacterias found in the gut altered the neuro-behavioural development of individuals, as observed in ASD. This was proved when these symptoms improved with changes in the gut microbiota, as a result of antibiotics or probiotics consumption by these children (Rege & Graham, 2017). https://psychscenehub.com/psychinsights/the-simplified-guide-to-the-gut-brain-axis/

Conclusion:

The bottom line to all these findings are that the gut can alleviate a range of physical and mental conditions, but; at the same time it can deteriorate the conditions too. To keep our gut healthy, it is important to make some dietary changes in our lives. Therefore it is important to consume prebiotic rich foods like yoghurt, whole grains, vegetables, fruits, etc.

References

Foster, J., Rinaman, L., & Cryan, J. (2017). Stress & the gut-brain axis: Regulation by the microbiome. Neurobiology of stress, 7. doi: 10.1016/j.ynstr.2017.03.001

Gordon., Betts, J. Anatomy and physiology (2013) . DeSaix, Peter., Johnson, Eddie., Johnson, Jody E., Korol, Oksana., Kruse, Dean H., Poe, Brandon. Houston, Texas. p. 9.
ISBN 9781947172043 .

Rege, S. and Graham, J., 2017. The Simplified Guide To The Gut-Brain Axis – How The Gut Talks To The Brain. [online] Psych Scene Hub. Available at: <https://psychscenehub.com/psychinsights/the-simplified-guide-to-the-gut-brain-axis/> [Accessed 19 November 2020].

Reigstad, C., Salmonson, C., Rainey, J., Szurszewski, J., Linden, D., Sonnenvurg, J., Farrugia, G., and Kashyap, P. (2015). Gut microbes promote colonic serotonin production through an effect of short-chain fatty acids on enterochromaffin cells. The FASEB Journal, 29(4), pp. 1395-1403

Robertson, R., 2020. The Gut-Brain Connection: How It Works And The Role Of Nutrition. [online] Healthline. Available at: <https://www.healthline.com/nutrition/gut-brain-connection> [Accessed 19 November 2020].

Saxena, R.; Sharma, V.K (2016). “A Metagenomic Insight Into the Human Microbiome: Its Implications in Health and Disease” . In D. Kumar; S. Antonarakis (eds.). Medical and Health Genomics . Elsevier Science. p. 117. doi: 10.1016/B978-0-12-420196-5.00009-5 .

Stewart, L., 2020. What’s The Link Between The Brain, Stress And The Gut Microbiome?. [online] Atlas Biomed blog | Take control of your health with no-nonsense news on lifestyle, gut microbes and genetics. Available at: <https://atlasbiomed.com/blog/stress-anxiety-depression-microbiome/> [Accessed 14 August 2020].