In some readings, we often see articles that encourage people to drink more water, emphasizing the importance of water for the functioning of the body. As the source of life, water is indispensable in our lives, but excessive water intake can also be harmful to the body and may even lead to water poisoning. Water poisoning refers to the pathological phenomenon in which the amount of water intake exceeds the body's ability to excrete it, resulting in the retention of water in the body, leading to a decrease in blood osmotic pressure and an increase in circulating blood volume. It is also known as water overload, water retention hyponatremia, or dilutional hyponatremia. Water overload is less common because, under the regulation of the nervous, endocrine, and renal systems, even if a large amount of water is ingested, the kidneys can excrete the water and maintain a balance between water intake and water output. In cases where the neuroendocrine and renal regulation of water is functioning properly, excessive water intake does not occur.
The kidneys are the main organs for excreting water, with strong urinary capacity. Even if most of the kidney's function is lost, it can still function normally. In order to maintain the balance of body water and prevent excessive urine output, the pituitary gland secretes antidiuretic hormone to regulate. When the body takes in too much water, the plasma osmotic pressure decreases, resulting in a decrease in the secretion of antidiuretic hormone and an increase in urine output. At the same time, due to the increase in blood volume and renal blood flow, urine output also increases. These two effects work together to excrete excess water from the body.
Water poisoning usually occurs when excess water is ingested for various reasons, but this amount is rarely exceeded in daily life. One common possibility is to drink a large amount of water immediately after sweating heavily. When a person sweats heavily, not only does the body lose water, but it also loses a lot of salt. If a large amount of water is consumed without replenishing salt, the salt concentration in the blood will decrease, the ability to absorb water will decrease, and some water will be quickly absorbed into the tissue cells, causing cellular edema and chronic water poisoning. At this time, a person may feel dizzy, thirsty, and in severe cases, may suddenly faint. In extreme cases, it may even be fatal.
In some cases, water poisoning may occur due to excessive water intake or excessive intravenous glucose infusion, especially in patients with poor heart or kidney function and infants with poor renal dilution function. In addition, after major surgery, the body is in a stress state, and the secretion of antidiuretic hormone is already excessive, leading to a decrease in urine output. If a large amount of fluid is given at this time, it can also cause water poisoning. For example, in infants with congenital megacolon, after a large amount of water is used to wash the intestines, a large amount of water is absorbed into the bloodstream through the intestinal wall, leading to water poisoning.
There are also some populations that need to be cautious about water poisoning, such as people with malnutrition, who have low plasma protein and low blood sodium levels, resulting in a decrease in extracellular fluid osmotic pressure. Water enters the intracellular fluid, causing a decrease in effective circulating volume and promoting the secretion of antidiuretic hormone, leading to a decrease in urine output and water retention.
In Western countries, there are some activities like "water drinking contests" where water poisoning is likely to occur. These contests are also the main cause of water poisoning deaths. In these contests, participants need to drink more than 10 liters of water in a few minutes. Another possibility is drinking excessive amounts of water due to the influence of some unknown psychotropic drugs. The side effects of these drugs can affect the secretion of antidiuretic hormone, making the patient feel thirsty and constantly drink water.
Editor's Note:
The amount of water required depends on the individual's environment, health condition, and food intake, and there is no specific standard value. Currently, there is no conclusive evidence to suggest that the body's need for water is related to an increase in temperature. If water intake is blindly increased, it may lead to symptoms of "water poisoning" such as weakness, increased heart rate, spasms, and coma.
