Is it really because I don’t sweat more that I urinate more frequently in cold weather?
I urinate more in cold weather, is it because I don’t sweat?
As the saying goes, "cold pee and hot fart" means that people tend to fart more in hot weather and urinate more frequently in cold weather.
In particular, no matter what the original temperature is, as long as the cold wave comes and the temperature drops sharply, there will be excessive urination or even frequent urination.
Why do I urinate more in cold weather?
One of the most widely circulated explanations is that people do not sweat in cold weather, and the water taken into the body can only be excreted through urine, so there will naturally be more urine.
This explanation seems very reasonable. It uses the simplest principles of addition and subtraction to "solve" complex physiological problems.
Unfortunately, however, this "intuitive" explanation is not correct.
So, what is the real reason for peeing more in cold weather?
The answer is not simple and involves at least three physiological mechanisms.
We know that humans are "warm-blooded animals" and are extremely sensitive to changes in environmental temperature. Even slight temperature changes will make timely adjustments to maintain the stability of core body temperature required for life activities.
Under the general ambient temperature of human life, the maintenance of heat balance is mainly through the contraction and relaxation of skin blood vessels to regulate skin blood flow, and to adjust the amount of heat loss by changing the temperature difference between the skin and the environment.
The temperature receptors distributed on the skin are extremely sensitive to the ambient temperature. As long as the temperature drops below 17, the exposed skin will feel cold, and the blood vessels in the skin will shrink to the maximum extent. This is also the reason for long-term exposure The physiological mechanism of frostbite (general frostbite usually occurs in late autumn and early winter, not the cold winter) is caused by people under 17 years of age.
The skin area of an adult is up to 2 square meters, making it the largest organ in the human body. The volume of blood circulating in it is very considerable and varies greatly.
Under suitable temperature, the blood flow of the whole body skin is about 250 ml/min.
Under high temperatures in summer, the maximum temperature can reach 6~8 liters/minute.
When the temperature drops below 17, assuming the whole body is naked, the minimum can be reduced to 20-50 ml/min.
In this way, as long as the temperature drops in cold weather, the blood volume in the peripheral circulation of the skin will be significantly reduced.
Where does the blood in the skin go?
The cold is "squeezed" into the blood vessels deep in the body, which is called "central circulation" in medicine; and the blood circulation in the skin is correspondingly called "peripheral circulation".
In cold weather, especially when the temperature drops sharply, the contraction of blood vessels in the skin "expells" more blood to the central circulation.
The capacity of the central circulation is relatively constant, and a sudden increase in a large amount of blood will cause an increase in blood pressure.
The increase in blood volume and blood pressure will stimulate the relevant volume and pressure receptors, sending signals to inhibit the hypothalamus from producing antidiuretic hormone.
We know that antidiuretic hormone is the main hormone in urine regulation. Increased secretion of antidiuretic hormone will act on the renal tubules to reduce the production of urine and retain body fluids.
When a person does not drink water for a long time, or when a person is dehydrated due to excessive sweating or diarrhea, it will stimulate the increase of antidiuretic hormone and reduce urine output.
On the contrary, cold weather inhibits the secretion of antidiuretic hormone and increases urine production, which manifests as polyuria.
Of course, regardless of the temperature, as long as there is no sudden drop, the human body has established a new body fluid homeostasis in this environment, and there will be no significant increase in urine.
Therefore, it is not accurate to say that you urinate more in cold weather; rather, it should be said that rapid cooling will lead to more urination.
Cold causes excessive urination, not only through the action of antidiuretic hormone, but also directly stimulates receptors on the skin, leading to a reduction in bladder capacity, which is commonly known as "small urine bubbles".
Therefore, cold can not only cause an increase in the absolute volume of urine, but also reduce bladder capacity and cause frequent urination; and frequent urination, in turn, will lead to more urination.
Of course, this stimulation requires lower temperatures, so frequent urination is more obvious during winter cold waves.
Not only will a sudden drop in ambient temperature cause polyuria and frequent urination, but local contact with low-temperature objects can also directly induce frequent urination or even urgency.
For example, washing hands with cold water in cold weather and stepping barefoot on cold ground will aggravate the feeling of polyuria and frequent urination.
This is because the "cold" temperature receptors on the skin can directly send signals to cause overactivity of the bladder's detrusor muscle, thereby inducing frequent urination and urgency.
Not sweating in cold weather is not the cause of excessive urination
On the contrary, people intuitively believe that not sweating in cold weather is not the cause of excessive urination.
The reason is simple. It is not just "cold weather" that prevents sweating.
Sweating is when the body's heat production is significantly higher than the non-evaporative (sweating) loss through the skin. Heat accumulates in the body, causing an increase in core body temperature.
At this time, the body temperature regulation center will activate the rapid heat dissipation mechanism of "sweating".
Sweating is extremely efficient in dissipating heat. If 1 gram of sweat completely evaporates on the skin, it can take away 56 kcal of heat.
Usually, the human body produces excess heat in a resting state without exercise. Only when the ambient temperature rises above 32°C and the temperature difference between the skin (the average temperature is 32°C) and the environment decreases to 0, evaporation occurs. Only when other heat dissipation pathways fail will the fast channel of sweating be activated to speed up heat dissipation.
Temperatures above 32 degrees Celsius are abnormally high and are not temperatures in people’s usual living environment.
Sweating is not the body’s conventional way of dissipating heat. Therefore, not sweating in cold weather will not make any “contribution” to excessive urination.