Water, the main constituent of our body, is essential for its functioning. At a moderate room temperature and at rest, the body always maintains its amount of water at a constant level. It is able to react to variations in water intake and loss to maintain a water balance . If the balance is broken and the body loses more water than it receives, then dehydration sets in. Dehydration is therefore the state which results from a lack of water in the body and which occurs when it loses more water than it acquires.
How do we get dehydrated naturally?
Every day, our body eliminates water, mainly through the emission of urine and sweat, but also through skin evaporation, breathing and stool.
These losses vary with physical activity, temperature, and consumption of fluids and food.
Water is eliminated mainly through urine , the product of blood filtration by the kidneys to get rid of liquid waste from the body. The body thus eliminates 500 ml to several liters of water per day.
Water loss is also due to perspiration , which helps regulate and maintain a constant body temperature. Sweat, excreted by the sweat glands on the surface of the skin, lowers the body's internal temperature. It is composed of 99% water and minerals, waste (urea, uric acid) which are therefore lost during perspiration. Perspiration varies according to physical activity, outside temperature, humidity, body temperature, clothing… We must therefore adapt our water consumption according to the circumstances.
The body naturally loses water through skin evaporation . The water hydrates the skin by diffusing from the dermis (the lower part) to the epidermis (the upper part) and then evaporates. In adults, this loss is about 450 ml per day, it varies with temperature and external humidity but is most often imperceptible.
Breathing also causes water loss, about 250-300 ml per day at rest. They increase with physical activity, altitude, lower temperature and humidity.
Finally, water loss through the stool is low in a healthy adult, at a rate of 200 ml per day.
If the natural and daily water losses are not compensated by sufficient hydration, the body becomes dehydrated.
What are the causes of dehydration?
The causes of dehydration are multiple, certain situations, pathologies or people are more at risk.
Common occasions
Excessive sweating during a heat wave, in the event of intense and prolonged effort or during an episode of fever is responsible for dehydration.
Certain drinks such as alcohol, coffee or tea increase diuresis and can cause dehydration.
Alcohol is often thought to quench thirst, but this is a misleading feeling. In fact, alcohol has diuretic properties that can help maintain a state of dehydration. There is then a dilution of urine and an increase in urine emissions. Excessive consumption of alcoholic beverages causes the body to “waste” water to eliminate the alcohol. Alcohol-related dehydration amplifies hangover symptoms such as dry mouth, intense thirst and headaches.
During the menstrual cycle, levels of estrogen and progesterone hormones fluctuate, which affects body hydration and can lead to episodes of dehydration. Blood loss during menstruation reinforces this dehydration.
Other situations, such as periods of fasting, can cause temporary fluid restrictions. Care must be taken not to allow dehydration to set in.
Pathologies
During episodes of gastroenteritis, diarrhea and vomiting lead to significant water loss and the situation can become serious if there is not sufficient fluid compensation, the person feeling too sick to drink enough fluids.
Chronic diseases, such as diabetes , can increase urinary excretion and therefore lead to dehydration.
Taking medications such as diuretics or taking too many laxatives leads to dehydration. Indeed, diuretics increase the excretion of urine and the loss of electrolytes (mineral salts such as sodium, potassium or chloride) in the urine.
People at risk
Anyone can be prone to dehydration, but for some people the risk is higher. Those who practice intense physical activity, for example, professional athletes. Older people are also particularly prone to dehydration because the thirst center functions less well than in younger people. Infants and children are at risk of dehydration, their bodies are very rich in water and the losses due to diarrhea or vomiting represent a higher proportion of liquids compared to adults.
What are the consequences of dehydration on the body?
The first sign of dehydration is the feeling of thirst , a signal from the body telling us that we need to drink more. With dehydration, the blood volume decreases and this drop in volume will trigger the feeling of thirst in response. But when thirst is felt, the body is already dehydrated.
Mild or moderate dehydration is manifested by a lack of energy, fatigue, difficulty concentrating, mood swings and headaches, because the body and the brain, less hydrated, are less efficient. Skin tissues are also less hydrated and lack electrolytes, causing redness, dryness and tightness of the skin and a dry, mushy mouth.
Dehydration leads to a decrease in diuresis (therefore a decrease in the volume of urine) and more concentrated and therefore darker urine.
Cramps, involuntary contractions of muscles at rest, during sleep or during physical exertion, occur due to poor hydration and lack of mineral salts.
Finally, dehydration promotes constipation. In fact, the stools are no longer softened enough by the water, intestinal transit is slowed down and the stools become harder.
If water loss is not compensated by fluid intake, dehydration worsens . The tissues dry out and the cells of the body begin to malfunction. You may then feel confused, dizzy from the drop in blood pressure, or faint. In the most serious cases, all the cells of the body are dehydrated and this leads to damage to organs such as the brain, kidneys or liver.
To prevent these consequences, any water loss must be compensated by food which represents 20 to 30% of water intake and drinks (70 to 80%), for a recommended intake of approximately 1 to 1.5 L of water per day.