60% of your body is water. But that number explains nothing. What matters is what water actually does in your body — and why, when it falls short, everything else fails first.
There is not a single process in your body that happens without water. Not one. From a muscle contraction to the formation of a thought, water is present as medium, transporter, and regulator. When someone says you should "drink more water," they are simplifying something worth understanding properly.
The percentage everyone cites and nobody explains
The adult human body is between 55% and 65% water, depending on age, sex, and muscle mass. Muscle holds more water than fat, which is why bodies with greater muscle mass have a higher water percentage. The brain and heart are approximately 73% water. The lungs, 83%. Bones — which many imagine as dry and solid — contain 31% water.
But these percentages are static. What the number does not show is the dynamism: your body loses between two and three liters of water every day through breathing, urination, sweat, and the insensible perspiration of the skin. That is water that needs to be replaced continuously — not once a day but across every hour of it.
"There is no substance on Earth more involved in life than water. It is the universal solvent, the medium of all biological reactions."
What water does inside you
Nutrient transport. Water is the primary vehicle of the circulatory system. Blood, which is approximately 90% water, carries oxygen, glucose, amino acids, and vitamins to every cell in the body. Without adequate water, this transport slows and cells receive less than they need.
Temperature regulation. The human body maintains an internal temperature of around 37 degrees Celsius regardless of the external environment. It does this primarily through sweat: when temperature rises, water evaporates from the skin and draws heat out of the body. Without enough water, this mechanism fails and the risk of heat stroke rises dramatically.
Joint lubrication. Synovial fluid, which acts as a shock absorber in the joints, is almost entirely water. When this fluid decreases due to dehydration, joints move with greater friction. This explains why many people with chronic knee or hip pain notice significant improvement when they increase their intake of quality water.
Waste elimination. The kidneys filter between 150 and 180 liters of blood per day. To do that work, they need water. Without adequate hydration, metabolic waste becomes concentrated, the risk of kidney stones rises, and the toxic load the body cannot eliminate accumulates in the tissues.
Digestion and absorption. Saliva, gastric juice, bile, and pancreatic fluids are all water-based. Digestion begins with water and ends with water. The large intestine absorbs water from waste before eliminating it; when there is not enough water available, the result is chronic constipation.
A loss of just 1% of body weight in water affects cognitive function. At 2%, physical performance drops measurably. At 3%, visible symptoms begin: headache, confusion, dry mouth. Most people live chronically between 1% and 2% dehydration without knowing it.
Why quantity is not enough
This is where the usual conversation about hydration falls short. It is not only how much water you drink. It is what kind, when you drink it, and what minerals it carries to your cells.
Cell membranes have protein channels called aquaporins that regulate water entry. These channels respond to osmotic pressure, which depends on the concentration of electrolytes in the extracellular fluid. Water without minerals — distilled water or low-mineralization filtered water — can pass through the digestive system without efficiently entering cells.
This explains something many people have experienced without understanding it: drinking water constantly and still feeling dehydrated. It is not a myth. It is physiology.
A starting point for this week
Before changing brands or buying a filter, observe. For three days, notice how you feel when you wake up: energy level, mental clarity, how your skin feels when you touch your face. Then add 500ml of water with a pinch of sea salt or with a little magnesium-rich mineral water before your morning coffee.
You do not need to measure anything else. Just notice if something changes. Your body has a lot to tell you when you give it what it needs.
With water and intention,
Luisa
