Water is the main component of the body: it represents around 60% of the weight of an adult’s body. A little more in infants (~75%), and a little less in elder persons (50%) (1).
Water, present in each cell and organs of the human body, plays several key roles. It acts first as a building material. Water is also a solvent, a reaction medium, a reactant and a reaction product. It helps to keep the body at the right temperature, through its evaporation at the surface of the skin. Moreover, water in the body transports nutrients to cells – it is the major component of blood (blood is 92% of water). Therefore, it maintains vascular volume and allows blood circulation which is essential for the good functioning of the different organs of the body. Water also helps remove waste products from the body, and helps it stay hydrated (1)
In other words, not drinking enough water may, sooner or later, lead to dehydration. That is how important water is!
An individual’s water needs depend on his age, his gender, the climate, his physical activity… (1-2). However, there is a recommendation: it is estimated that a healthy sedentary adult, living in temperate climate, should drink in average 1.5 liters of water per day (1).
An insufficient water intake disturbs the water balance. Indeed, to maintain the water balance, the water inputs must be equal to the equal outputs. Water intakes are composed of: the water you drink (~ 1.5 liter per day*), the water you eat (on average 675 ml per day) and the water your body produce (around 300ml per day).
Water outputs include: the water you lose via urine (around 1.6 liters per day), the water lost through the skin (approximately 450ml per day) and the lungs (~300ml/d), and finally the water in the feces (~200ml/d). (1)
When you maintain the water balance, you stay well hydrated. On the other hand, if the water intakes are lower than the water losses, you can experience a hydration deficit and thus one step further becoming dehydrated.*For a healthy sedentary adult living in temperate climate
Let’s specifically talk about people who do not drink enough every day : For instance, they drink 1 liter per day instead of the recommended 1.5 liter for a healthy sedentary adult living in temperate climate. Let’s have a look at the consequences on short, medium and long term…
Thirst and dry mouth feeling. Indeed, any decrease in blood volume caused by an insufficient hydration leads to the activation of receptors located in the wall of the vessels, as well as the emission of a signal that is going to stimulate the thirst center in the brain (3). Concerning elderly persons, the thirst feeling is often altered because of the aging process (4).
Other signs of mild-to-moderate dehydration. These persons often feel tiredness, headaches, dizziness and muscle weakness… (1)
Higher risk of urinary tract infection. Indeed, not drinking enough leads the hypophysis to exude an anti diuretic hormone (ADH), which increases the re-absorption of water at the kidney level, and can cause the reduction of the urinary volume and to more concentrated urine (3,5). This allows microbe outbreaks and increases the risk of urinary tract infections. As you may know, drinking enough every day reduces the risk of urinary tract infections (5).
Some talk about drier and wrinkled skin; others affirm it increases the cardiovascular risk, but that has not yet been proven.
As discussed above, not drinking enough water may lead to insufficient hydration or one step further to dehydration. So let’s enthusiastically drink your 8 glasses of water* every day, and appreciate them, with the feeling to indulge yourself!*For a healthy sedentary adult living in temperate climate; 1 glass = 200 ml References: 1- Jéquier E, Constant F. Water as an essential nutrient: the physiological basis of hydration. Eur J Clin Nutr 2010, 64: 115-23.