Water is not just a drink we turn to when we feel thirsty, but rather it is an essential element of life and a medium in which countless vital processes take place within the body. Through it, nutrients and oxygen are transferred, cells get rid of waste, and chemical reactions continue that maintain the functioning of the organs and the balance of the body.
Dehydration occurs when the body loses more water than it takes in, and this may be accompanied by a loss or disturbance in sodium and other electrolytes, especially with severe sweating or vomiting and diarrhea.
However, a distinction must be made between thirst and dehydration, as thirst is a physiological signal that prompts a person to drink, while dehydration is a condition in which fluid deficiency has already begun. Thirst is not always an early and reliable indicator, especially in the elderly.
Water…the environment in which life pulsates
Blood, lymph, the fluid surrounding cells, and the fluids inside them are all aqueous environments that play essential roles in transporting nutrients, oxygen, and waste, and completing biochemical reactions.
The brain needs water to complete its metabolic processes, the heart depends on an appropriate volume of blood to continue pumping, the lungs need moist surfaces to exchange gases, and the kidneys use water to regulate electrolytes and get rid of waste, while the digestive system needs it for digestion and absorption.
Muscles and nerves also depend on the balance of water and electrolytes to generate electrical signals, contraction, and movement.
This simple molecule is formed from two hydrogen atoms and an oxygen atom, but it is so important that it represents a basic condition for life as we know it.
How does the body know that it needs water?
The thirst system begins before we reach for a cup of water. When blood osmolarity, that is, the concentration of dissolved substances in it, increases, specialized receptors pick up this change. Other receptors also sense a decrease in blood volume or pressure in the circulatory system.
These signals reach areas of the brain, including the hypothalamus, which plays a pivotal role in regulating water balance, and the desire to drink is generated.
At the same time, the secretion of the antidiuretic hormone “Vasopressin” increases, which prompts the kidneys to increase the reabsorption of water, so its loss with urine decreases and urine becomes more concentrated.
Thus, the body works on two simultaneous paths: it forces us to search for water, and it tries to preserve what it has until the fluids it needs reach it.
From a sip of water to a living cell
After drinking water, it begins to be absorbed through the digestive system, then it is distributed between the blood and the fluid surrounding the cells and inside the cells, according to a delicate balance governed by the movement of water and dissolved materials.
The concentrations of electrolytes on both sides of the cell membrane are not the same. Sodium is more concentrated outside the cell, while potassium is more concentrated inside it. These differences are necessary to maintain the cell’s size, electrical functions, and ability to communicate.
One of the most prominent mechanisms that maintains this difference is the “sodium-potassium pump,” which in each cycle transports 3 sodium ions out of the cell in exchange for two potassium ions into it, consuming a portion of cellular energy.
This fine geometry is essential for maintaining osmotic balance and electrical potential of cells. When severe dehydration is accompanied by significant disturbances in electrolytes, symptoms such as weakness, convulsions, and disturbance of consciousness may appear, and the heart rhythm and functions of vital organs may be affected.
Symptoms of dehydration
- Early signs: thirst, dry mouth, headache, fatigue, poor concentration, and less or darker urine than usual.
- Advanced symptoms: With increased fluid loss, dizziness, weakness, rapid heartbeat, and decreased urine output may appear, in an attempt by the body to maintain the volume of blood circulation and perfusion of vital organs.
- Severe dehydration: confusion, fainting, severe weakness, and significant or no urine output, along with rapid pulse and breathing, and cold extremities, which are signs that require urgent medical evaluation.
What increases the risk of dehydration?
- Environmental factors: Heat increases water loss through sweating, and water loss increases in some dry environments and high altitudes, so attention should be paid to hydration during heat waves, traveling, and working in harsh climatic conditions.
- Physical exertion: During activity, the body loses water and sodium through sweat, and the loss increases with the length of the exertion and the increase in temperature. Someone who sweats for hours may need to replace both water and electrolytes.
- Medical causes: Vomiting, diarrhea, and fever are among the most prominent causes of fluid loss, and some medications, especially diuretics, may increase water loss.
- Lifestyle: Coffee, tea, and other caffeinated beverages contribute to total daily fluid intake when consumed in moderation, and do not usually cause dehydration in people who are accustomed to them. But drinking too much sugary or caffeinated beverages is not an ideal way to hydrate, and should not always replace water.
Who is most vulnerable?
- Infants and children: They can lose water and electrolytes quickly through vomiting and diarrhea, and may develop dehydration within a short time.
- Elderly people: Their thirst response may be weakened, and chronic diseases, difficulty moving, and some medications increase the risk of dehydration.
- People with chronic diseases: High blood sugar sometimes leads to increased water loss through urine, while patients with heart or kidney diseases may need to restrict fluids, so there is no single amount suitable for everyone.
What does a lack of water do to the body?
- In the short term: Fluid deficiency may be associated with headache, fatigue, and poor attention and mental performance, and its effect increases with heat and physical exertion.
- On the digestive and urinary system: A lack of water leads to more concentrated urine, while drinking an appropriate amount of fluids is one of the most important ways to reduce the risk of some types of kidney stones. A lack of fluids may also contribute to constipation in some people.
- Serious complications: Severe fluid loss may lead to decreased blood volume and pressure and decreased access to organs, leading to hypovolemic shock. Severe disturbances in sodium and other electrolytes can also lead to neurological symptoms and convulsions.
- Skin: An obvious lack of fluids may be associated with dry skin, but drinking additional amounts of water in a person who is already getting what he needs does not alone guarantee more hydrated skin. The skin barrier, topical care, nutrition and sun protection are more complex factors, and the evidence on the benefit of increased hydration for the skin is still limited.
How do we protect ourselves?
- The 8 Cups Rule: Not a medical law that applies to everyone. The need for water varies according to age, body size, food, activity, climate, and health condition. The body also obtains water from drinks and foods.
- Personal need: Some clinical estimates use figures around 25 to 35 milliliters of fluid per kilogram of body weight per day in certain circumstances, but this is not a general formula for how much water each person should drink. Sweating, heat, illness, pregnancy, and some heart and kidney diseases may change the need significantly.
For most healthy people, responding to thirst, noticing the color of urine, and making sure to increase fluids in the heat and exertion help maintain hydration.
- Hydrating foods: Foods rich in water, such as cucumbers, watermelon, cantaloupe, citrus fruits, and other fruits and vegetables, contribute to the body’s total water intake, in addition to fiber and nutrients.
- Rehydration solutions: When diarrhea or vomiting, water alone may not be enough, because the body loses water and electrolytes together. Standard formula oral rehydration solutions are the best option when needed. Homemade solutions require careful adherence to the amounts, because excess salt or sugar may be harmful, especially for children.
Water in a hotter world
As exposure to heat waves increases, staying hydrated becomes more important, especially for outdoor workers, the elderly, and children, as sweating increases the loss of water and electrolytes and increases the burden on the heart and kidneys.
But the issue does not stop at the amount of water an individual drinks. The availability of safe and sufficient drinking water represents one of the foundations of public health, as water shortages or contamination threaten the ability to drink safely, maintain hygiene, and prevent disease.
Thus, the story of water begins from within a microscopic cell, but extends to one of the biggest health issues in the world: that humans remain able to access safe water whenever they need it.