The principal constituent of living organisms, water regulates all the chemical reactions necessary for the vital functions. It transports nutrients, allows exchange between the inside and outside of cells, guarantees the action of gastric juices and, by means of transpiration, helps maintain body temperature. Sixty five percent of the human body is made up of water and each day 6% of this is eliminated in the urine, feces, sweat and respiration. To make up for water loss, 2-3 l of water should ideally be consumed each day in fresh water-rich foods (particularly vegetables, milk and yoghurt) and drinks. The best of these is water as it contains no calories and can be drunk freely at any time of day. Balanced intake of water encourages diuresis, elimination of toxins and blood circulation. Vice versa, a lack of water leads to dehydration, manifested by tiredness and a drop in physical and psychological efficiency. In the most serious cases, it seriously jeopardises the body’s balance.