Fluid Requirement - This Is How Much Water The Body Needs

How much fluid does the body need?

Water is vital. More than 50 percent of the human organism consists of water - in babies it is even around 70 percent. Fluid is constantly excreted through the skin, intestines (stool), kidneys (urine) and when breathing. Therefore, fluids must be continuously absorbed. 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.

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• How much should you drink a day?
• When should infants start drinking water?
• Can you drink too much?
• What happens if you are dehydrated?

Water has many different functions. It is contained in every body cell and all body fluids - for example in saliva, gastric juice, in the lymphs or in the blood. Among other things, water is necessary to maintain heat regulation (sweating). The transport of nutrients, metabolic end products and breathing gases depends on water. All chemical reactions in the body also require water.

How much should you drink a day?

The need for water differs and depends on various factors (e.g. energy expenditure, ambient temperature and food composition, the salt content of the food and physical activity). Depending on their age, young people 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: approx. One ml of water per one kcal per day. At 2,500 kcal, that equates to 2.5 liters per day for adults.

Note According to the Austrian Food Pyramid, at least 1.5 liters of non-alcoholic, low-energy drinks such as water, mineral water, unsweetened fruit or herbal tea or highly diluted fruit and vegetable juices should be consumed daily.

When should infants start drinking water?

From the tenth month onwards, infants should regularly drink fluids when they switch to family meals - in addition to breastfeeding or baby food. (Tap) water and unsweetened fruit teas are suitable (mate, green and black teas are not suitable). Special children's teas or drinks are not required. If you have a high fever, severe diarrhea or vomiting, it may be important to drink earlier - talk to your pediatrician.

Can you drink too much?

Water poisoning (intoxication) is very rare, but can occur when the elimination capacity of the kidneys is overwhelmed. One possible consequence is the development of brain edema. The maximum amount of fluid that an adult can ingest over a long period of time is approximately ten liters. In order to suffer from acute water poisoning, an adult (70 kg) would have to drink six liters of water within a short period of time. With infants (one month old = " and four kilograms) this risk threshold can be reached much more easily with 0.4 liters of water and with small children (one year old = " and ten kilograms) with 0.9 liters of water.

The following symptoms of excessive water intake include:

• Difficulty breathing (dyspnoea)
• Water retention in the tissue (edema)
• Cramps, confusion, loss of consciousness and even coma
• Symptoms of heart failure
• Acceleration of the heartbeat (tachycardia)

Certain diseases (e.g. kidney dysfunction) are usually responsible for water overload.

What happens if you are dehydrated?

A lack of fluids shows up quickly through various signs. Depending on the extent of the defect, this includes:

• Thirst,
• Dry mouth, decreased saliva and urine production,
• A headache,
• Weight loss,
• decreased skin tension, swollen tongue, difficulty swallowing,
• Constipation,
• accelerated heartbeat, increased body temperature,
• thickened blood,
• severe limitation of physical and mental performance, confusion,
• Muscle spasms as well
• Circulatory collapse.

Dehydration and possible consequences often affect older people, especially with swallowing difficulties. More information can be found under Drinking in old age.

Severe water loss can lead to serious physical damage. Without replacement of the liquid there is a risk of death. Substances that are normally excreted with the urine can no longer be adequately eliminated by the body after two to four days.

The need for fluid is increased, for example, during physical exertion, during sport, at high or very low temperatures and during fever, vomiting and diarrhea. The body also needs more fluids during pregnancy and breastfeeding, and more should be drunk.

Note Water is not only contained in beverages, but also in various foods - especially fruit and vegetables.

Further information is available from:

• Non-alcoholic drinks (food pyramid)
• Correct use of heat
• Eating and drinking in the heat