Water is essential for life. More than 50 percent of the human organism consists of water – in infants it is even about 70 percent. Fluid is constantly excreted through the skin, the intestines (stool), the kidneys (urine) and during breathing. Therefore, fluids must be taken in continuously. Adults should drink a minimum of 1.5 liters of water from beverages per day. Those who drink too little must expect reduced physical performance.
Water has many different functions. It is contained in every body cell and all body fluids – for example, in saliva, gastric juice, lymph and blood. Among other things, water is necessary to maintain heat regulation (sweating). The transport of nutrients, metabolic waste products and respiratory gases depends on water. All chemical reactions in the body also require water.
How much should you drink per day?
The need for water varies and depends on various factors (e.g. energy metabolism, ambient temperature as well as food composition, salt content of food as well as physical activity). Depending on their age, adolescents and adults should consume between 30 and 40 ml of water per kilogram of body weight per day.
As a rule of thumb for healthy adults: about one ml of water per one kcal and per day. At 2,500 kcal, this results in 2.5 liters for adults per day. For sports and fitness, you need more due to the amount you lose from sweating. We recommend using a 1 gallon water bottle for such activities, as they also usually have markings for the amount of water you should drink for each time of the day.
When should infants start drinking water?
Infants should drink fluids regularly – in addition to breastfeeding or formula – from the age of ten months with the transition to a family diet. (Tap) water and unsweetened fruit teas are suitable (mate, green and black teas are not suitable). Special infant teas or drinks are not necessary. In case of high fever, severe diarrhea or vomiting, drinking earlier may be important – talk to the pediatrician.
Can you drink too much?
Water intoxication is very rare, but can occur if the kidneys’ ability to excrete is overwhelmed. A possible consequence is the development of cerebral edema. The maximum amount of fluid that an adult can take in daily over a longer period of time is given as about ten liters. To suffer acute water intoxication, an adult (70 kg) would have to drink six liters of water within a short period of time. For infants (one month old and four kilograms), this risk threshold can be reached much more easily with 0.4 liters of water, and for toddlers (one year old and ten kilograms) with 0.9 liters of water drunk.
What happens when there is a lack of fluid?
Lack of fluids and possible consequences often affect older people, especially those with swallowing difficulties. For more information, see Drinking in old age.
Severe water loss can lead to serious physical damage. Without fluid replacement, life is in danger. Substances that are normally excreted in the urine can no longer be sufficiently eliminated by the organism after only two to four days.
The need for fluids is increased, for example, during physical exertion, sport, high or very low temperatures and fever, vomiting and diarrhea. The body also needs more fluid during pregnancy and breastfeeding, and more should be drunk.