Why is there a saying that "cold urine and hot farts"? A little physiological secret from the perspective of biomechanics

1. Introduction

"Cold urine, hot farts, poor people lie" is a proverb and poem that is popular among the people. I don't know which talented farmer brother said it. Today, I will ignore "poor people lie" and talk about the scientific issues of "cold urine, hot farts".

Cold urine and hot farts is a common name among the people. It usually refers to the increase in urine output under the stimulation of cold factors. If it is hot, there may also be more farts (Figure 1).

Figure 1 Schematic diagram of “cold urine and hot farts”

Literally, this question is directly related to temperature. So, when it comes to "cold urine" and "hot farts", how does temperature affect our physiological reactions?

In fact, the two "unspeakable" body reactions of "cold urine" and "hot farts" may seem like unrefined topics, but they actually hide the mysteries of biomechanics. Let's unveil their mysterious veil together!

2. The scientific explanation for “cold urine”

On a cold winter day, you may have had this experience: you just went to the bathroom, and a short while later, you felt the urge to urinate again. Is it because our body has turned into a "faucet" in the cold? Actually, it is not. This is not a joke, but a natural reaction of the human body in a cold environment. Let's take a deeper look at the biomechanical principles of the "cold urine" phenomenon.

Humans are warm-blooded animals and are sensitive to changes in ambient temperature. In order to maintain the stability of the core temperature required for human life activities, the human body will make timely adjustments as the temperature changes. When the human body senses a drop in external temperature, in order to maintain body temperature, the autonomic nervous system will issue instructions to cause the blood vessels on the surface of the skin to contract and reduce heat loss. This physiological reaction leads to a decrease in blood on the surface of the body and a tendency for blood pressure to rise. In order to balance this change, the kidneys begin to exert their regulatory function and increase the amount of urine produced. In this way, excess water and salt are excreted from the body through urine, helping to maintain stable blood pressure.

Scientific research has also confirmed this. In one study, scientists placed a group of volunteers in a low-temperature environment and monitored their urine production. The results showed that the volunteers in the cold environment produced significantly more urine than the control group in a warm environment. In a low-temperature environment of 10°C, the participants' kidneys excreted about 30% more urine than in a warm environment of 24°C. This data intuitively shows the impact of a cold environment on kidney function and urine output.

In addition to physiological reactions, the "cold urine" phenomenon is also related to neural regulation. Cold stimulation is transmitted to the central nervous system through skin receptors, triggering a series of nerve reflexes. These reflex signals affect the sensory nerves and motor nerves of the bladder, regulating the muscles of the bladder to contract. Overactive bladder detrusor muscles may induce frequent urination and urgency, leading to an enhanced perception of urination.

It can be seen that the "cold urine" phenomenon is the body's natural reaction to cold environments, and it adapts to changes in external temperature through a series of physiological and neural regulatory mechanisms. Understanding these mechanisms can help us better understand the body's physiological reactions in different environments, and pay more attention to and take care of our own physical needs in daily life to avoid unnecessary physical injuries.

3. The scientific explanation for “hot farts”

If "cold urine" is the product of cold environments, then "hot farts" are the "flavor" of hot environments. On hot summer days, you may find that you seem to fart more than usual. What's going on? Let's take a deeper look at the biomechanical principles of the "hot fart" phenomenon.

When the body is in a hot environment, in order to dissipate heat and maintain normal body temperature, the blood vessels on the surface of the skin will expand, allowing more blood to flow to the body surface. This physiological reaction leads to a decrease in the amount of blood flowing through the digestive tract, which slows down intestinal motility and the digestion process of food. At the same time, a high temperature environment will also affect the motility of the gastrointestinal tract, causing food to stay in the intestines longer, providing intestinal bacteria with more "fermentation" time. In the process of decomposing food, these bacteria will produce a large amount of gas, which we commonly call farts.

Scientific research has found that when the participants were in a high temperature environment of 35°C, their gastrointestinal motility was about 30% slower than in a normal temperature environment. This means that food stays in the intestines longer, providing intestinal bacteria with more opportunities for fermentation.

When food stays in the intestines for a longer time, intestinal bacteria will decompose it to produce gases, which mainly include nitrogen, carbon dioxide, methane, etc. As the gas is produced and accumulated, the intestines will push the gas to the anus through peristalsis, and eventually it will be discharged from the body in the form of farts.

In addition, a high temperature environment may also cause the human body to sweat more, affecting the body's water and electrolyte balance, which will indirectly affect the normal function of the digestive system and further aggravate the production of farts.

It can be seen that the "hot fart" phenomenon is the body's natural reaction to a hot environment. Understanding these mechanisms can help us regulate our physiological needs in daily life to avoid "internal injuries" caused by holding back farts.

Ahem! Do you sometimes feel bloated, unable to fart, and uncomfortable when you catch a cold? I'll give you a secret recipe that's not inherited from your ancestors: warming your stomach can help relieve bloating and promote the release of farts.

The biomechanical principles involved can be explained from the following aspects: (1) Promote intestinal peristalsis: When the stomach is stimulated by warmth, the peristalsis of the intestinal muscles will increase. This helps push the gas in the intestine toward the anus, making it easier to expel the gas from the body. (2) Relieve intestinal spasms: Sometimes the intestinal muscles may spasm, making it difficult for the gas to be discharged smoothly. A warm environment can soothe the intestinal muscles, relieve spasms, and restore the normal peristaltic function of the intestine. (3) Increase intestinal gas diffusion: A warm intestinal environment can promote better diffusion of gas in the intestine to the intestinal wall, making it easier for the gas to be discharged from the intestine (the gas acts as a lubricant, forming a fluid dynamic lubrication effect - I won't go into details here). (4) Relax the anal sphincter: A warm environment can relax the anal sphincter, making it easier to open, thereby helping the gas to be discharged. Friendly reminder: The method of heating the stomach should be moderate to avoid overheating, which will lead to the consequence of "not farting but scalding the skin", which is not worth the loss.

4. Little-known facts about “cold urine and hot farts”

Scientists have also conducted many interesting experiments on the study of "cold urine and hot farts". For example, one study found that the temperature of urine is usually around 36°C, while the temperature of farts is as high as 37.5°C. This shows that urine is indeed "colder" than farts - "cold urine and hot farts" is real.

(1) Why is urine cold? As blood flows through the kidneys to form urine, the urine gradually cools down. The temperature of urine produced by the kidneys is usually lower than body temperature. As urine flows through the urethra, the heat exchange between the urine and the urethral mucosa causes the urine to cool further. The cooling of urine is also related to the length of the urethra. The male urethra is longer, and as urine flows through it, it comes into contact with the mucosa with a lower temperature around the urethra, causing the urine to cool more. The female urethra is shorter, and the degree of urine cooling is relatively low. This is why male urine is "colder" than female urine. It can be seen that the process of urine cooling actually involves the principles of thermodynamics.

(2) Why are farts hot? The temperature in the intestines is usually higher than the external environment. Therefore, during the production of farts, they will be affected by the temperature in the intestines, making the temperature of the farts higher. Secondly, the temperature of farts is also related to pressure. When the gas in the intestines accumulates to a certain extent, the human body will fart and expel the gas out of the body through the small outlet of the anus. According to the law of isochoric change of gases - Charles' law, we know that for a certain mass of gas, when the volume remains unchanged, the pressure is proportional to the temperature. When the gas in the intestines accumulates to a certain extent, the gas pressure increases and the temperature also rises accordingly. In addition, when farting, the contraction of the anal sphincter will generate heat, which will also squeeze the fart flow, further causing the temperature of the fart to rise. It can be seen that the increase in the temperature of the fart actually involves the law of isochoric change of gases.

5. Conclusion

Although "cold urine and hot farts" are embarrassing episodes in our lives, they contain rich biomechanical principles. Understanding this knowledge can not only help us better cope with the body's reactions in different environments, but also make us more understanding and tolerant in embarrassing moments, and more humorous and calm in daily life.

Cold urine and hot farts, I accept them all.

Physiological reaction, no need to be surprised.

No worries, no worries about health.

Although it is embarrassing, it makes sense.

After reading this short article, flush the toilet with ease.