Water, Source of Life: Everything You Need to Know About Hydration and Its Benefits

Water in the human body: some staggering figures

The human body is an extraordinary water-based machine. Every cell, every organ, and every biological function depends on water to operate correctly. The brain is 80% water, blood is 90%, and the lungs are 83%. Without constant renewal of these reserves, the organism gradually begins to fail.

What is less commonly known is that the human body does not store water. Unlike fat, which constitutes an energy reserve, water must be continuously replenished. Every day, we lose between 2 and 3 liters of water through sweating, breathing, urine, and stool. This loss must be compensated daily to maintain the body's water balance.

Official ANSES recommendations

The French Agency for Food, Environmental and Occupational Health and Safety (ANSES) regularly publishes precise recommendations regarding water intake according to age groups. These figures are the standard for health professionals in France.

What is water actually used for in the body?

Water is not just a simple drink. It is the universal medium in which all the body's biological reactions take place. Here are its main, often misunderstood functions:

• Transporting nutrients: Water is the vector that carries vitamins, minerals, carbohydrates, and proteins to cells via the bloodstream
• Eliminating waste: Toxins, urea, creatinine, and other metabolic waste are dissolved in water and eliminated by the kidneys and skin
• Thermal regulation: Sweating and evaporation allow the body to maintain its temperature at 37°C in all circumstances
• Joint lubrication: Synovial fluid, composed of water, protects joint cartilage and reduces friction during movement
• Digestion: Saliva, gastric juices, bile—all are composed of over 90% water and are essential for digestion
• Brain function: The brain depends on water for the transmission of nerve impulses and the production of neurotransmitters
• Organ protection: Cerebrospinal fluid protects the brain and spinal cord, and amniotic fluid protects the fetus
• Beauty and skin: Proper hydration maintains skin elasticity, reduces wrinkles, and provides a luminous complexion

Signs of poor hydration

Dehydration sets in gradually, and its symptoms are often wrongly attributed to other causes. Learn to recognize your body's warning signals:

Hydration at every stage of life

Infants: constant vigilance

Infants are the group most vulnerable to dehydration. Their body surface area is proportionally larger than adults', leading to faster water loss. Their thermal regulation mechanism is still immature, and they cannot communicate their thirst.

Before 6 months, breast milk or formula is sufficient to cover all of a baby's water needs. After 6 months and upon the introduction of solid foods, water can be offered between meals.

Children and adolescents: growing needs

Growth is a period of high water demand. Muscles, bones, and the developing brain need optimal hydration to build correctly. However, children are often distracted by their activities and forget to drink, especially during physical activity.

Studies show that 30 to 40% of school-aged children arrive in class in a state of mild dehydration, which directly affects their concentration and school performance.

Active adults: between stress and sedentary lifestyles

Adults face two opposing pitfalls: physical overactivity that increases water loss, and sedentary office work that makes one forget to drink. In both cases, chronic dehydration is common.

According to an INSERM study (2023), 75% of French adults do not hydrate enough on a daily basis and suffer from mild chronic dehydration without realizing it.

The elderly: when thirst disappears

With age, the sensation of thirst gradually dulls. The kidneys also lose their ability to concentrate urine, increasing water loss. Dehydration in the elderly is one of the leading causes of hospitalization in France, with over 50,000 hospitalizations per year directly linked to this phenomenon.

Water quality: just as important as quantity

Drinking enough is essential, but drinking quality water is just as important. As ANSES regularly reminds us, water contains contaminants that, when accumulated over the long term, can have harmful effects on health.

Water laden with nitrates, pesticides, lead, or microplastics—even if consumed in the right quantity—does not properly fulfill its biological functions and can instead introduce undesirable substances into the body. The solution? Combine proper hydration AND purified water.

Practical tips for better daily hydration

• The glass-upon-waking rule: Drinking a large glass of water first thing in the morning rehydrates you after 8 hours of fasting and jumpstarts your metabolism
• Don't wait for thirst: Thirst already signals mild dehydration. Drink regularly, about every hour
• Space out your intake: 8 to 10 glasses of water spread throughout the day are better absorbed than a large amount all at once
• Increase water-rich foods: Cucumber (97%), tomato (95%), watermelon (92%), soup—these contribute to daily hydration
• Reduce diuretics: Coffee and alcohol increase urinary output. For every coffee you drink, compensate with an extra glass of water
• Use reminders: Mobile apps or hourly alarms help maintain the hydration habit
• Adapt to the season: In summer and during heatwaves, increase intake by at least 500mL per day