Metabolic and biochemical reactions
Water is not just a transporter of nutritional elements. It plays an active role in our metabolic processes.
Breaking down food
Through a process called hydrolysis, water molecules are part of the biochemical breakdown of proteins, lipids and carbohydrates, which are structurally complex foods, into units more absorbable by the body.
Internal creation of water
On the other hand, different metabolic reactions create water internally. This water is referred to as "metabolic" or "endogenous". The body of a sedentary person produces about 250-350 ml of metabolic/endogenous water a day.
Sources: European Food Safety Authority (2011) scientific opinion on dietary reference values for water. EFSA J 8, 1459–1506; Pivarnik J.M., CRC Press, 1994 Pivarnik, J.M. and Palmer, R.A., Water and electrolyte balance during rest and exercise, in Nutrition in Exercise and Sport, Eds., CRC Press, Boca Raton, FL, 1994