Why your body is made up of more water than you think

All the things water does in your body

As you read this, billions of cells are hard at work in your body. They communicate, transport, filter and repair. And in all these processes, one substance plays a pivotal role – a substance so commonplace that we hardly notice it: water.

Water is involved in virtually every process in your body – quietly, unobtrusively, yet indispensably. It is far more than just a drink. It is the foundation on which your body functions.

How much water is in your organs?

The adult human body consists of around 60% water – in women, the proportion is slightly lower, at around 55%, because body fat content is generally higher and fatty tissue stores less water than muscle tissue. But the figure alone does not tell the whole story. This is because water is distributed very differently throughout the body.

Your lungs consist of about 83% water – making them the organ with the highest water content in your body. This surprises many people, as we tend to think of air first when we think of the lungs. But the thin layer of water on the inner surface of the alveoli is crucial for gas exchange: only in this way can oxygen and carbon dioxide pass between the air and the blood.

Muscles and kidneys follow, with a water content of around 79%. This makes sense for the kidneys: they filter around 170 litres of blood daily and produce around 1 to 1.5 litres of urine from it. Without water, this vital detoxification process would be impossible.

The brain and heart contain around 73%. The brain is particularly sensitive to fluctuations in water balance. Even a water loss of 1.5% of body weight impairs concentration, learning ability and memory – as shown by studies from the Georgia Institute of Technology, published in the journal ‘Medicine & Science in Sports & Exercise’. A study by Liverpool John Moores University from 2025 also demonstrated that cortisol release – the stress hormone – was increased by 50% in dehydrated subjects.

Your skin contains around 64% water, and even your bones are still made up of around 31% water. In newborns, the total water content is as high as around 78% – it decreases steadily with age.

What water does in your body

Building material: Every one of your cells contains water. It gives them shape and stability. Without water, your cells could neither grow nor divide. Water is not merely present passively – it actively participates in biochemical reactions, such as the breakdown of nutrients.

Transport: Your blood consists of over 90% water. It carries nutrients, minerals and oxygen to where they are needed – to your organs, muscles and brain. At the same time, it transports waste products away, which are excreted via the kidneys, liver and lungs.

Cooling system: When your body produces heat – during exercise, when you have a fever, or on hot days – water regulates your temperature. Sweating is nothing more than the body’s own air conditioning system. During an hour of intense exercise, your body can lose up to a litre of sweat.

Solvent: Vitamins, minerals and enzymes can only function in dissolved form. Water creates the conditions necessary for your metabolism to work. Without water, the entire enzyme system would grind to a halt.

Detoxification: Through the kidneys, liver and skin, water helps your body eliminate toxins and waste products. Your kidneys alone filter around 170 litres of blood per day – a feat that would be impossible without sufficient water. Without enough fluid, these detoxification processes grind to a halt, and waste products build up.

Joint fluid & shock absorbers: Water is a component of synovial fluid and the cerebrospinal fluid that surrounds and protects your brain and spinal cord. It cushions impacts and ensures your joints remain supple.

Communication: Water is a good conductor of electrical impulses. These impulses form the basis of communication between your nerve cells. Inadequate hydration can impair the efficiency of this signal transmission – with a direct impact on your thinking speed and memory.

Why quality matters

When your brain consists of almost three-quarters water and your lungs of over 80%, it becomes clear: water is not just any component of your body. It is the main component of your most vital organs. And that also means: the quality of the water you drink has a direct influence on what your body is made of and how well it functions.

It is also interesting to look at the different stages of life. In newborns, the body consists of almost 78% water – it is literally the stuff that new life is made of. This proportion decreases during childhood, and in old age it can fall to below 50%. At the same time, the sensation of thirst diminishes with age. Many older people chronically drink too little without realising it – with measurable consequences for circulation, kidney function and brain performance.

Imagine your body as a house. Water isn’t just the paint on the walls – it’s the foundations, the walls and the roof. The quality of your water isn’t a side issue. It’s the stage on which your health plays out.

And that is precisely why it is worth taking a closer look: how much do you drink? And above all – what do you drink?