It has long been believed that an average human being should drink about 1.5 liters of water a day, or 8 glasses a day. However, these figures differ according to the research they are drawn from, and the different types of morphologies observed. Water is an essential need for the body, so its consumption is essential. But how much do you really need?
The body’s water requirements are specific to a person’s morphology, lifestyle and climate. Water represents about 60% of the body weight. But every day, a significant amount escapes from the body. Studies show that the body of a person of average size would spend more than 2 liters of water a day. The excesses are mainly eliminated by the urine, which serves to evacuate the waste produced by the body, but also through breathing, sweating and tears. These losses are offset by diet, which represents around a liter, and liquids that are drunk.
It is therefore necessary to hydrate throughout the day, even when thirst is not felt. Indeed, with aging, people feel less the need to drink and the risk of dehydration is possible. In case of high temperatures (heat causes additional water loss), physical activities, breastfeeding and illnesses, it is advisable to ensure proper hydration of the body. The risk of dehydration is defined by body weight, and may be due to insufficient water consumption. The first signs of chronic dehydration may be a darker urine than usual, dryness in the mouth and throat, headaches and dizziness, and very dry skin and intolerance to heat. In order to remedy this, it is advisable to drink as much as possible, although some studies have shown that absorbing too much water can be dangerous.
Drinking too much would be bad for your health
Too much and too fast fluid intake in the body, called hyponatremia, could be harmful. The kidneys, which take care of fluid intake, can regulate only one and a half liters of water per hour. In fact, drinking too much water would cause the cells to swell in the blood, which could lead to a disorder of brain function. The concentration of the intra-plasma sodium ion is also greatly reduced due to the presence of water in the plasma. However, hyponatremia most often results from pathologies such as potomania or an excess of infusions: cases of this disorder remain rare and affect only a tiny number of people.
Studies have been conducted to define what would be the real water requirement of the body. The figures vary between 1 and 3 liters per day, it is advisable to drink about two liters daily. But as we saw earlier, it depends on the morphology, the environment and the way of life of the person. This statement must be nuanced and placed in the contexts to which it belongs. These two liters do not include water in the true sense of the term, but all liquids that go through food and water-based drinks (tea, coffee, juice). The theory of 8 glasses therefore refers to the totality of liquids consumed during a day. This recommendation stems from a study by the Institute of Medicine, which suggested that each calorie of food intake was equal to one milliliter of water. For example, 1,900 calories a day is equivalent to 1,900 mL of water (1.9 L). However, confusion occurrs when people forget that the food eaten already contained water, so it would not be necessary to drink 2 liters of extra water. However, other studies say the opposite: they should, according to them, consume between 2.5 and 3 liters in addition to food.
The answer then remains vague and impossible to define, because many researches contradict each other and give each different results. The recommendation to drink 1.5 liters of water a day can be considered a myth, but it remains necessary to ensure the body’s proper hydration throughout the day.