Various studies show that drinking about 1.5 liters of water per day, ie 8 drinks a day. However, the figures differ according to the research, and the different types of morphologies observed. Water is an essential need for the body, so its consumption is essential. But is it really limited to 1.5 liters a day?

The needs of the body in water are specific to the morphology of a person, his way of life and the climate. Water accounts for about 60% of 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 per day. Excesses are mainly eliminated by urine, which serve to evacuate waste produced by the body, but also through breathing, sweating and tears. These losses are offset by the food, which is around one liter, and liquids that are drunk.

It is therefore necessary to hydrate throughout the day, even when the thirst is not felt. Indeed, with aging, people feel less need to drink and risks of dehydration are possible. As in the case of high temperatures (heat causes additional water loss), physical exertion, breastfeeding and illness, it is advisable to ensure proper hydration of the body. The risk of dehydration is defined as a function of body weight, and may be due to insufficient and prolonged water consumption. The first signs of chronic dehydration can be dark urine, dryness in the mouth and throat, headache and dizziness, and very dry skin and heat intolerance. In order to remedy this, it is advisable to drink as much as possible, although some studies have shown that absorbing too much water could be dangerous.


Too much and too fast consumption of fluids in the body, called hyponatremia, could be harmful. The latter would not be taken care of by the kidneys, which can regulate only a liter and a half of water per hour. Indeed, drinking too much water would cause the cells to swell in the blood, which could cause a disturbance of brain function. The concentration of the intra-plasma sodium ion is greatly reduced because of the presence of water in the plasma. However, hyponatremia most often results from pathologies such as potomania or an excess of infusions: the cases of this disorder remain rare and affect only a tiny number of people.


Studies have been carried out to define 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 affirmation must therefore be qualified, and put back 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 pass through food and water-based beverages (tea, coffee, juice). The theory of the 8 glasses thus designates the totality of liquids consumed during a day. This recommendation originated in a study by the Institute of Medicine, which suggested that each intake calorie was equal to one milliliter of water. Thus, a consumption of 1,900 calories per day is equivalent to 1,900 mL of water (1.9 L). The confusion occurred when people forgot that the food already contained water: therefore, it would not be necessary to drink 2 liters of extra water. However, other studies say the opposite: they should consume between 2.5 and 3 liters in addition to food.


The answer is vague and impossible to define, because much research contradicts each other and gives different results. The recommendation to drink 1.5 liters of water a day can be considered a myth, but it remains necessary to ensure its proper hydration throughout the day for the good of its body.