Drinking too much water could be fatal! The myth of eight glasses of water a day has long been debunked by Guokr. What's more terrifying is that kidney specialists have found that the "8x8" theory—eight 8-ounce glasses (about 1.8L) of water daily—is not only baseless but could be extremely dangerous! Drinking this much water doesn't bring health; instead, it invites hyponatremia and water intoxication, and in severe cases, it can even be fatal!
66% of the human body is water, and most of the blood is water. This water nourishes cells and the intercellular matrix through blood circulation. However, this water is escaping the body every second through various means, such as sweating, excretion, and exhalation. Replenishing lost water is necessary, but overdoing it can be lethal!
Are you still believing in the 8x8 theory? The "8x8" rule of eight glasses of water a day is a classic myth, and Guokr's Myth Buster debunked it mercilessly as early as last year.
The truth is, not only is there no scientific research to support the "8x8" theory, but for a healthy adult living in a temperate or tropical zone and getting moderate exercise daily, drinking that much water won't make you healthier; instead, it increases the risk of hyponatremia and the possibility of water intoxication!
The mystery of hyponatremia! Hyponatremia, which can be described as "insufficient salt in the blood," is a condition where the concentration of sodium in the blood is below 135 mmol/L (the normal range is 135-145 mmol/L). Severe hyponatremia can lead to water intoxication and is accompanied by symptoms such as headaches, fainting, nausea, vomiting, frequent urination, and confusion.
The kidneys filter excess water and salt from the body through the renal tubules. If we drink too much water in a short period, causing the kidneys to expel it too slowly, the excess water will eventually enter the cells, causing them to swell like balloons.
Most cells in the body have some room to expand because fat and muscle are elastic. Nerve cells, however, are tightly packed within the hard skull, sharing the limited space with blood and cerebrospinal fluid, leaving almost no room for expansion. Therefore, if these nerve cells also "swell into balls," it will lead to the devastating disaster of cerebral edema. The rapid swelling of brain cells can cause the brain to expand, leading to brain tissue damage, sudden coma, respiratory depression, brain herniation, and even death. A 28-year-old woman in California died after drinking about 6 liters of water in three hours during a water-drinking contest, subsequently experiencing severe vomiting, explosive headaches, and ultimately death.
How does water intoxication occur? Healthy kidneys can normally excrete 800-1000 ml of water per hour, so drinking 800-1000 ml per hour is perfectly fine. Of course, the water we consume doesn't all come from drinking water, and in most cases, our kidneys can handle our normal fluid intake. However, if a large amount of water is consumed suddenly in a short time, our kidneys will be "overwhelmed," and this water will be forced into the cells, causing them to become water-intoxicated.
In addition to drinking large amounts of water in a short time, abnormal secretion of antidiuretic hormone (ADH) is also one of the causes of water intoxication. Joseph Verbalis, director of internal medicine at Georgetown University Medical Center, said: "Simply drinking too much water doesn't always cause water intoxication. Water intoxication occurs when excessive water intake is combined with increased ADH secretion." ADH is synthesized by the hypothalamus and secreted into the blood by the pituitary gland. Its main function is to signal the kidneys to retain water. When the body senses water stress (such as during a marathon), its secretion increases. At this point, even if a person has already drunk a lot of water, it stubbornly commands the kidneys to continue retaining water!
For example, during a marathon, stress increases the body's secretion of ADH, reducing the kidneys' excretory function to 100 ml/h. In this situation, even if you are sweating profusely, drinking 800-1000 ml of water per hour could still lead to water intoxication! There have also been reports of people at nightclubs, after dancing all night and sweating profusely, dying from water intoxication after drinking large amounts of water.
How much water should I drink? Theoretically, water intake should balance with sweat loss. But how do you measure sweat loss? If you calculate it strictly, a person needs to consume about 2000-3000 ml of water per day (including water from food). However, you really don't need to go through all that trouble. As long as you are healthy and your sense of thirst is not impaired by age or medications that regulate the nervous system, then drink when you feel thirsty and stop when you no longer feel thirsty! There is no need to drink extra water out of "guilt" for feeling thirsty, and certainly no need to keep a daily chart to track your water intake!
However, you don't need to be so cautious that you're afraid of drinking too much water and dying. In normal circumstances, our powerful kidneys will expel the excess water. So, in our daily lives, the ultimate solution to "how much water to drink" is simply to drink when you're thirsty and stop when you're not. Also, never think you have big kidneys and participate in any "water-drinking contests"!