The term “gut feeling” is a commonly heard phrase that is used to describe a visceral emotion or urge, as opposed to one that is produced from reasoning or logic. This expression is one of many used that mesh the brain’s cognitions and the sensations felt in the stomach together. For example, when someone is preparing themselves for a situation that induces a degree of uneasiness in them, they may claim that they feel nauseous. The saying that one has butterflies in their stomach is also often used to explain the feeling of nervousness. These expressions, although used figuratively, have been proven to have scientific roots.

The stomach, often referred to as a “second brain”, contains bacteria that has a role in producing neurotransmitters that are found within the gastrointestinal tract. Through these transmitters, the brain and the stomach have a method of communication, which leads to various gastric sensitivities that correspond with different emotions. In a UCLA research study, done on mice, researchers observed that the amount of bacteria present within the stomach had a notable influence on the demeanor and wellbeing of the mice. On one hand, the mouse that had more bacteria within its stomach experienced higher stress levels and moved significantly less than the mouse that possessed a lower amount of gastric bacteria. The study highlights the impact that the stomach has on the experience of emotions related to anxiety and distress, which closely relate to the aforementioned expressions, such as feeling butterflies, when an individual faces an uncomfortable situation. 

The relationship between the brain and the stomach is established even before birth, as the stress experienced by a mother also impacts the wellbeing of the fetus. Studies have shown that the children of mothers who endure an increased amount of stress during pregnancy possess a decreased amount of gastric bacteria. This mother-child physiological interconnectedness continues as the child begins to consume either breast milk or milk formula. Children that consume breast milk are found to have different levels of bacteria within their stomachs than those who are given formula milk. Breast Milk-fed children are found to have comparatively less neural inflammation and have higher neural regulation. This, therefore, positively impacts the brain’s functioning through taking part in the production of neurotransmitters that take part in regulating emotions. 

Just as the brain responds to the stimuli that take part in determining the amount of bacteria in the stomach, the stomach responds to external stressors that impact the brain. Lifestyle choices such as an individual’s diet, the amount of stress that one experiences, and the constancy that one has in their life all play a role in determining the levels of bacterium within the stomach. Within the intestines, the bacteria has the ability to permeate through the walls of the gastrointestinal tract and enter the surrounding area. This intestinal permeability is shown to have an inflammatory response on the body. Abrupt adjustments within one’s life have been linked to being one of the causes of intestinal permeability. Although still developing, research has suggested that the body’s reaction to this inflammation can contribute to mental health disorders such as anxiety and depression.  

The research surrounding the interdependence between the brain and the stomach is only on the surface of its development. Knowledge of the link between the two has opened doors of opportunity to discover ways to improve an individual’s mental health condition through focusing on improving the levels of gastric bacteria. Recognizing the inner workings of the network between the two also gives insight to how various life choices can improve both our mental and gastric wellbeing. 

References :

Clapp, M., Aurora, N., Herrera, L., Bhatia, M., Wilen, E., & Wakefield, S. (2017, September 15). Gut microbiota's effect on mental health: The gut-brain axis. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5641835/

MacDonald,J(2017,July 26). Your Gut, Your Emotions | JSTOR Daily. Retrieved from https://daily.jstor.oeg/your-gut-your-emotions