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Turns out your gut feeling is real. Recent research has found that bacteria in the gut can affect people’s mental state, leading to mood, cognition and behavioural problems. The enteric nervous system (ENS) is a lesser known part of our body’s nervous system located in our gut. Because the enteric nervous system uses the same type of neurons and neurotransmitters that are found in the central nervous system, some medical experts call it our “second brain.”
And yet according to Traditional Chinese Medicine (TCM), this is hardly news. It has been known for centuries that the Small Intestine (i.e. the gut) and the Heart (which governs the Mind) are connected while the Large Intestine and the Lung (which governs the skin and immunity) are connected.
What is enteric nervous system?
The enteric nervous system (ENS) controls the digestive system, connecting through the central nervous system (CNS) and sympathetic nervous system.
In particular, the enteric nervous system determines the movements of the gastrointestinal tract, regulates gastric acid secretion, changes in local blood flow and the gut hormones release, and interacts with the immune system in the gut. It forms during the last few months of gestation (in humans) and continues to develop after birth.
Transmissible spongiform encephalopathies, autistic spectrum disorders, Parkinson disease, Alzheimer disease, amyotrophic lateral sclerosis, and varicella zoster virus (VZV) infection are examples of disorders with both gastrointestinal and neurological consequences. [1]
The gut-brain axis
The gut-brain axis (GBA) is a communication system between the brain and the trillions of bacteria, fungi and viruses living within your intestines. It consists of bidirectional communication between the central and the enteric nervous system. The gut and brain are connected through thick nerve cables that transfer information via chemicals called neurotransmitters in both directions. Many of these neurotransmitters such as glutamate, GABA, serotonin, and dopamine are at least partially, if not fully, made in the gut and heavily influenced by diet.
What is more to this important control is the microbiome inside the guts. The composition of gut bacteria can have a profound impact on mental health and the functioning of the nervous system. A healthy diet plays a significant role in shaping this microbiome by promoting the growth of beneficial bacteria and stopping the accumulation of harmful ones. Nutrition can also influence the communication along the gut-brain axis, further affecting the links between the gastrointestinal tract and the nervous system.
"The gut microbiota strongly influences our metabolic, endocrine, and immune systems, as well as both the peripheral and central nervous systems. Recently, a dialogue between the gut and lung microbiota has been discovered..." - Journal of Oncology, 2017 [2]
TCM theory on the Gut-Brain Connection
In traditional Chinese medicine, the link between the gut and all of the body’s organs has been recognised for thousands of years. The theory of Zang Fu is a collective name for the various Yin and Yang organ systems identified in TCM. A Yin organ is called a Zang 臟 and a Yang organ is called a Fu 腑.
Each Zang organ is associated with a Fu organ, creating five Yin-Yang organ systems. Each of these organ systems corresponds with one of the five phases of transformation. This is shown below.
Zang | Fu | Phase | Spirits |
Spleen | Stomach | Earth | Yi |
Lung | Large intestine | Metal | Po |
Kidney | Urinary bladder | Water | Zhi |
Liver | Gall bladder | Wood | Hun |
Heart | Small intestine | Fire | Shen |
The key systems related to the Gut-Brain connection in the TCM theory is Spleen/Stomach, Heart/Small intestine and Lung/Large intestine.
Spleen and Stomach interaction and its importance
Spleen and Stomach is extremely important in the TCM theory, is it regarded as the “acquired constitution”. This is because they are the site of production of Qi’, blood and fluids which are vital substances for life. The Spleen transforms our food into useful material. Without this vital source of energy, we could not even survive. What is more, Spleen grounds the Yi 意 in the Five spirits. It has to do with thought, intellect, and comprehension, as well as intention and creativity.
The Spleen plays a major role in digestion. It separates and transforms useful nutrients from waste products. On a physical level, a weak Spleen can result in poor digestion of food. On a spirit level, a weak Spleen, thus a weak Yi as a result. Just as the Spleen and Stomach help us digest our food material, the Yi helps us digest our conceptual reality. The meaning of Yi - thoughts or intention, is what appears in your mind as preconception, idea, opinion, before action (by Liver, Hun) and determination (by Kidney, Zhi). Poor digestion disturbs our thoughts and vice versa. That is why overthinking or excessive intellectual work could harm our digestion and in the long run overall health. They may lack clear intention, have brain-fog, chronic fatigue and feel unmotivated.
Heart and Small Intestines interaction and its importance
The Heart in the TCM theory is regarded as the master of mind. It works with a special type of Fire energy called “Sovereign Fire”. Fire in this context means power, warmth and light which also explains the function of the Heart system: (1) power for the circulation of blood (with a supply of Qi energy from the Stomach and Spleen), (2) warmth in temperature and human touches, (3) light as a guiding faith/beacon in the spirit, also the glow that one would shine in a good health.
The Small Intestines uses the Heart’s Fire energy to burn down the substances together with the Stomach and Spleen then absorbs nutrients. In return, the nutrients and energies “evaporate” and move up to support the Heart. The key point is that this is a interdependent and bidirectional relationship that should not be mixed up with the anatomical small intestine which merely just break down food with enzymes. Let’s use a metaphor like this: imagine the TCM Small Intestines as a machine to release enzymes, the Heart is the switch and dosing adjustments while the Spleen is the manufacturer of the enzymes; once the enzyme breaks down the food then the nutrients and wastes go to the places where it suppose to be.
Together the Heart (with the assistance of Small Intestines) provides the following functions:
Determines consciousness and cognition
Feels and assesses the emotions
Is responsible for perceptions, feelings and senses (with Po)
Is responsible for thinking, intelligence, wisdom, ideas (with Yi)
Controls sleep and memory (with the Kidney)
Governs the senses (sight, hearing, smelling, taste)
Is responsible for autonotic function and immune reaction (with Hun)
Lung and Large Intestines interaction and its importance
Research on allergy has recently uncovered an apparent co-occurrence of allergies in skin and the lungs, a phenomenon that has been coined “atopic march”. A positive correlation has been found between gut microbiota at birth and the development of asthma and skin eczema later in life. Chinese medicine has long described a functional relationship between the large intestine and the lungs, and between the lungs and skin. [3]
The topic of Lung and Large Intestine is a lot more complex and more scientific evidence are available. This will be discussed in another article.
Rao, M., Gershon, M. The bowel and beyond: the enteric nervous system in neurological disorders. Nat Rev Gastroenterol Hepatol 13, 517–528 (2016). https://doi.org/10.1038/nrgastro.2016.107
Rea Bingula, Marc Filaire, Nina Radosevic-Robin, Mathieu Bey, Jean-Yves Berthon, Annick Bernalier-Donadille, Marie-Paule Vasson, Edith Filaire, "Desired Turbulence? Gut-Lung Axis, Immunity, and Lung Cancer", Journal of Oncology, vol. 2017, Article ID 5035371, 15 pages, 2017. https://doi.org/10.1155/2017/5035371
Leung, Hiu Yu & Leong, Pou Kuan & Chen, Jihang & Ko, Kam-Ming. (2017). Inter-Organ Relationships among Gut, Lung and Skin beyond the Pathogenesis of Allergies: Relevance to the Zang-Fu Theory in Chinese Medicine. Chinese Medicine. 08. 73-81. 10.4236/cm.2017.83006.