The connection that Korean medicine explained as liver qi stagnation leading to flank pain and digestive symptoms can now be explained far more scientifically through the concept of the gut-brain axis. Rather than being simply independent organs, the brain and gut are intimately connected neurologically, endocrinologically, and immunologically, just like two friends engaged in constant conversation.
When we experience stress or feel anxiety, the brain immediately detects this and activates the hypothalamic-pituitary-adrenal axis. When this axis operates, the stress hormone cortisol is secreted. This cortisol affects the entire body, exerting a direct impact particularly on the digestive system. When cortisol levels rise, intestinal motility can become abnormally accelerated or diminished, and it can increase intestinal permeability, inducing leaky gut syndrome. When the intestinal wall loosens, waste products, toxins, and microorganisms inside the intestine can easily penetrate into the bloodstream, which can trigger a systemic inflammatory response leading to chronic fatigue or decreased immunity.
In addition, the gut possesses so many neurons that it is called the 'second brain', forming what is known as the enteric nervous system. The enteric nervous system is directly influenced by the autonomic nervous system and is sophisticated enough to operate independently without instructions from the brain. Stress stimulates the sympathetic nerve within the autonomic nervous system, and when the sympathetic nerve dominates, digestive function declines and intestinal motility becomes irregular. Conversely, the parasympathetic nerve, which is activated in a comfortable and stable state, promotes the secretion of digestive juices and facilitates smooth intestinal motility. When stress persists, this sympathetic nerve becomes excessively activated, causing an imbalance in intestinal motility and ultimately producing symptoms similar to irritable bowel syndrome, such as abdominal pain, gas, diarrhea, and constipation.
A crucial nerve here is the vagus nerve. The vagus nerve is the largest nerve directly connecting the brain and gut, extending from the brain to various organs including the laryngopharynx, heart, lungs, and stomach, playing a central role in the parasympathetic nervous system. The vagus nerve regulates intestinal motility and digestive enzyme secretion, interacts with the gut microbiota, and regulates inflammatory responses, contributing in diverse ways to maintaining our body's homeostasis. When stress becomes chronic, the activity of the vagus nerve declines, which can lead not only to gut dysfunction but also affect mental health issues such as depression and anxiety. This aligns directly with the view in Donguibogam that liver qi stagnation accompanies mental symptoms like stuffiness and sighing alongside digestive symptoms.
Furthermore, approximately 95% of serotonin, known as the happiness hormone, is produced in the gut. Serotonin is involved in various biological functions including mood regulation, sleep, and appetite; when gut health deteriorates, serotonin production is also disrupted, which can lead to mood swings or feelings of depression. Imbalance in the gut microbiota is also an important factor. Continued research indicates that when the balance between beneficial bacteria and harmful bacteria is disrupted, it induces intestinal inflammation, and these inflammatory substances can travel through the blood to the brain, impairing brain function.
In conclusion, flank heaviness and digestive symptoms such as abdominal pain, gas, constipation, and diarrhea are not merely isolated intestinal issues. They can be seen as the result of a disrupted signaling system between the brain and gut due to stress, which brings about an overall imbalance spanning the autonomic nervous system, hormones, and gut microbiota. Our body was expressing all of this distress under the name of liver qi stagnation, signaling through flank pain and digestive symptoms. Therefore, when addressing these symptoms, one must remember that body and mind are one.
