Water is key.

Water is the major constituent of the human body. About two parts out of three in our body is water. Strangely enough, our body cannot produce enough water by metabolism or obtain enough water by food ingestion to fulfil its needs. As a consequence, we need to pay attention to what we drink throughout the day to ensure that we are meeting our daily water needs, as not doing so may have negative health effects. Especially during periods of high demands on our body (e.g. exercise) the water and fluid intake’s importance increases.

Water is the main constituent of cells, tissues and organs and is vital for life. Despite its well-established importance, water is often forgotten in dietary recommendations, and the importance of adequate hydration is not mentioned.

This blog post addresses the key functions of water in the human body, leaving no room for doubt as to how essential adequate water intake and management is for a balanced health.


Water as building block

Water, present in each cell of our body and in the various tissues and compartments, acts first as a building material. A lot of the molecules found in the body use water as one of the most important and frequent building blocks. Therefore, water needs are higher during periods of growth (childhood) and intensive training (high turnover of cells because of training adaptation).

Water as carrier

Water is essential for cellular balance (homeostasis) because it transports nutrients to cells and removes waste away from cells. Water also maintains the total vascular volume (the volume of blood) and so allows blood circulation, which is essential for the function of all organs and tissues of the body. Thus, the cardiovascular and respiratory systems, the digestive tract, the reproductive system, the kidney and liver, the brain and the peripheral nervous system, all depend on adequate hydration to function effectively.

Water as thermoregulator

Water has a large heat absorbing capacity, which contributes to limiting changes in body temperature in a warm or cold environment. Water has a large capacity for vaporization of heat, which allows a loss of heat from the body even when ambient temperature is higher than body temperature. When sweating is elicited, evaporation of water from the skin surface is a very efficient way to lose heat. It should be noted however, that sweating is not the only way our bodies lose water. A lot of water is lost through respiration in the lungs and urine production in the kidneys.

Water as lubricant and shock absorber

Water forms, in combination with viscous molecules, lubricating fluids for joints, with digestive enzymes and proteins fluids for saliva, gastric and intestinal mucus secretions in the digestive tract and for mucus in airways secretions in the respiratory and the genito-urinary tract.

By maintaining the cellular shape of each individual cell, water acts as a shock absorber during walking or running. This function is also important for the brain and spinal cord, and is particularly important for the fetus, who is protected by a water cushion.

Bieke Bekaert