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Questions and common beliefs about water


Water plays an important role in the functioning of the human body, as it is one of its major components

Water is not an essential component of the human body

FALSE: Water plays an important role in the functioning of the human body, as it is one of its major components! Indeed, the human body is mainly composed with water, whose percentage decreases when the body ages, from 75% for infants to 60% for adults and 50% for elder persons. These proportions vary in the different organs as well.

While water represents 73% of an adult’s  brain, it constitutes 83% of his lungs, 79% of his kidneys and of his muscles. That is to say, if you don’t drink enough water throughout the day, you will feel the effects of this lack.

You don’t necessarily need to drink water, because you lose little amount of it every day

FALSE: Every day, in temperate climates, a healthy sedentary adult loses on average 2.5 liters of water per day. You lose water through urine (around 1.6l/day), through skin (perspiration) (around 450ml/day), through water steam eliminated when breathing (around 300ml/day) and through the stools (around 200ml/day). That’s why, everyday, you need to compensate these water losses with drinks and food.

The water you need to stay well hydrated is only contained in drinks

FALSE: The water you need to maintain your water balance comes mainly from beverages but food brings water that contributes to the overall daily water intake.

Some foods are richer than others, like fruits and vegetables which can contain 90% to 95% of water. It is estimated that, in average, the water contained in the food contributes to about 675ml of total daily water intake.

Moreover, our organism produced every day between 250 to 350 ml of water. Thus, to compensate for the daily water losses of 2.5 liters, a healthy sedentary adult living in temperate climate should drink 1.5 liters of water per day. Thus, the food you eat and an adequate intake of water (8 glasses of water per day – 1 glass = 200 ml for adults), will help you to maintain your water balance.

When you are thisty, drinking one or two sips of water is enough

NO, it’s not enough: Actually, drinking one or two sips just helps to ease your thirst without necessarily restoring your water balance. In fact, the thirsty feeling tells you when your body is dehydrated, more or less depending on your thirst intensity. To maintain the water balance, you need to drink water regularly throughout the day, before the sensation of thirst appears.

Drinking while eating impedes digestion

FALSE: Drinking 1 to 2 glasses of water during a meal does not prevent the digestion process to start in the stomach. This process is above all related to the secretion of digestive enzymes. So remember to drink water regularly throughout the day, including mealtimes.

Reference: Mitchell HH et coll. The chemical composition of the adult human body and its bearing on the biochemistry of growth. The Journal of Biological Chemistry, 1945:  625-637.
Jéquier E, Constant F. Water as an essential nutrient: the physiological basis of hydration. European Journal of Clinical Nutrition (2010) 64, 115-123

One Response to Questions and common beliefs about water

  1. Water found in coffee is never considered as being part of the recommended daily intake of water.
    Why is that so?? Thank you,

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