The relationship between the lungs and large intestine, and the heart and small intestine, is a concept in Traditional Chinese Medicine (TCM). Many specialized terms in TCM can be difficult to understand, so we can set those aside and focus on the structure and patterns of the human body to see if these patterns correspond with TCM’s assertions.
We know that the heart beats, and besides generating blood pressure, it also produces a lot of heat. Some may ask why we say there is heat; this is common knowledge. Continuous beating generates heat—try jumping and see for yourself. From a physics perspective, kinetic energy produces thermal energy.
The natural property of heat is to radiate outward and upward. If not utilized, this heat will be completely lost, which is an inefficient model where energy is not recycled. The reason we say the human body is intelligent is that it has a good energy recycling pattern.
The lungs are located outside and above the heart, and most of the heat generated by the heartbeat will reach the lungs. In TCM, the lungs are referred to as ‘metal’ (金, jīn) because metal is the most heat-resistant. When heart fire reaches the lungs, it causes lung heat, a process known as ‘fire overcoming metal’ (火克金, huǒ kè jīn). The worse the lung condition, the more likely one is to experience lung heat. For instance, individuals with rhinitis may find that even slight exercise causes heat to rise in their nasal passages, indicating lung heat.
In TCM, while it is said that the lungs are ‘metal’, it is clear that they are not truly heat-resistant. The lungs are often described as delicate organs that are easily harmed; how could they not be afraid of heat? How do the lungs handle this heat? The lungs govern respiration. The air that enters through the respiratory tract can facilitate heat exchange in the lungs. Think of an air conditioner in summer, which removes hot air from indoors and replaces it with cooled air.
The heat generated by the heartbeat is originally directed upward. When it reaches the lungs, the room-temperature air inhaled through the respiratory tract is comparatively cool, and this cool air descends, helping to cool down the body. While cooling, it also transports heat downward, where does it go? It goes to the intestines.
We know that the primary site for nutrient absorption in the body is the small intestine. Why can the small intestine absorb nutrients? From a biochemical perspective, it is due to digestive fluids such as pancreatic juice and bile that extract nutrient molecules from food. Many chemical reactions require heat to occur; even though enzymes and coenzymes are present in the body, they still need some heat, albeit not at high temperatures.
Where does this heat come from? It comes from heart fire. The heat from the heartbeat, propelled by lung qi (气, qì), reaches the small intestine. Thus, TCM considers heart fire as ‘sovereign fire’ (君火, jūn huǒ), while the small intestine is seen as ‘ministerial fire’ (相火, xiàng huǒ). One sovereign and one minister, they are interrelated. There is a phrase, ‘warm-hearted’ (热心肠, rè xīn cháng), which means that truly warm-hearted people are very enthusiastic and have abundant energy.
Having sufficient energy in the body depends on the small intestine’s ability to absorb nutrients effectively. Nowadays, many people are indifferent, which can be attributed to psychological and physiological reasons; the physiological reason being insufficient energy in the body. However, not all seemingly warm-hearted individuals are healthy; some may be overextending their energy.
For the small intestine to absorb nutrients, pressure is also a factor. A physics teacher in middle school once explained that at high altitudes, the air is thin, and the pressure is relatively low, making it harder to cook food compared to plains, where higher temperatures are required. In other words, the more sufficient the pressure, the better it is for cooking food.
This is why we use a pressure cooker to stew bone soup in a shorter time. In my area, people love to drink pork rib and lotus root soup. Cooking at room temperature takes a long time, and some lotus roots do not become tender. However, using a pressure cooker, regardless of the type of lotus root, it can be made tender. This is the effect of pressure.
The small intestine extracts nutrient molecules from food in a manner similar to cooking food. The human body also has internal pressure, generally believed to be equal to external atmospheric pressure. However, this is true for healthy individuals; those who are ill may not experience this. If internal pressure is insufficient, the small intestine may struggle to process food completely, leading to diarrhea.
From my experience, many people suffer from insufficient internal pressure. The simplest test is to pinch your nose and close your mouth tightly, applying slight pressure. If you can hear a clear popping sound in both ears, that indicates normal pressure. Many people report that only one ear pops, and some have a softer sound. These are all signs of insufficient pressure.
To regulate internal pressure, one must use qi (气, qì) for adjustment; breathing is the only way for the body to take in gas, so breathing has a qi-replenishing effect. After practicing related exercises for a while, you may feel a noticeable sensation of gas in your stomach or intestines. The main difference between chest breathing and abdominal breathing is that chest breathing keeps the qi in the chest cavity, while abdominal breathing allows qi to reach the intestines.
Some may say that intestinal bloating is a good thing. However, intestinal bloating means that gas cannot escape, which is certainly not good. If waste gas cannot exit the intestines, and clean air cannot enter, how can that be beneficial? There must be an exchange of qi for it to be good.
The above explains the relationship between the heart and small intestine. What about the relationship between the lungs and large intestine? The positional relationship between the heart and lungs is very similar to that of the small and large intestines. The heart is inside and below the lungs, while the small intestine is inside and below the large intestine. This may reflect their interrelated nature. We know that the large intestine has the function of reabsorbing water, which is why stools are not loose.
How does the large intestine reabsorb water? It is primarily due to the heat from the small intestine. The heat from the heart rises to the small intestine, and its property of rising and radiating outward is perfectly aligned with the large intestine being outside and above the small intestine. The heat from the small intestine rises and distills the water within the large intestine, allowing it to reabsorb water. Additionally, the expansion and contraction of heat means that with this heat, the large intestine does not contract too tightly, facilitating the passage of food residues, allowing for smooth bowel movements.
Many people may say that this is nonsense. First of all, this theory is not mine; I cannot invent a theory. This is a TCM theory that I previously could not understand. The reason for my misunderstanding is that most people focus solely on pipes, blood vessels, and blood. However, the heat mentioned in the article does not need to be transmitted through blood vessels or other pipes. Look at the natural atmosphere; does it require pipes for transmission?
Secondly, I have not discussed physiology and biochemistry because it is unnecessary. Textbooks have long taught that physical changes precede chemical changes. What I have discussed here are all physical changes. The physical changes in the body are primarily related to temperature and humidity, and these subtle changes can significantly affect pipes, blood vessels, and blood, as well as cellular activity. Therefore, adjusting these changes can lead to healing.
Many people do not understand TCM, partly due to a lack of basic physics knowledge, or even if they have learned it, they do not know how to apply it, lacking a summary of natural laws and life experiences. In fact, as long as you have some physics knowledge and apply it to the human body, you can understand TCM. On the other hand, there is a common misconception that the body’s temperature, whether overall or locally, remains constant. They never consider that illness arises from errors in the body. Cells are very sensitive to temperature and humidity; even small changes can affect their efficiency.
The above views are for reading and thought-provoking purposes only and should not be used for clinical treatment, nor do they represent the author’s suggestion for everyone to seek TCM treatment.
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