Fluid balance
Fluid balance keeps the intake and loss of fluids in equilibrium – according to the German Nutrition Society (DGE), adults need to drink around 1.5 litres a day.
Ausführlich erklärt
Your body is 50 to 60% water – in babies, as much as around 75% – and loses about two and a half litres of it every day through urine, breath, skin and stools. Your fluid balance makes sure this loss is replaced: thirst, kidneys and hormones regulate how much you drink and how much is excreted. Losing as little as 1 to 2% – about a litre at 70 kg – measurably reduces concentration, mood and performance.
The German Nutrition Society (DGE) recommends around 1.5 litres a day from drinks for adults; solid food such as fruit, vegetables, soup and yoghurt provides roughly another 0.7 to 1 litre. In hot weather, during exercise, with a fever or while breastfeeding, requirements rise considerably – during exercise, you can lose 0.5 to 1 litre of sweat an hour. Children need less, but more regularly: about 0.8 litres at nursery age, around 1 litre at primary school, and 1.2 to 1.5 litres for teenagers.
The best thirst quenchers are water and unsweetened tea; juice diluted at a ratio of 1:3 is a good choice for children and during exercise. Soft drinks, iced tea and pure juices provide lots of sugar and calories without filling you up. Coffee counts too, by the way – it doesn't drain more fluid than it provides.
For weight loss, water is a quiet helper: it has no calories and fills your stomach, and in one study, adults who drank a large glass before every meal lost around two kilos more over twelve weeks. Drinking also affects what the scales show: salt, carbohydrates and heat cause the body to hold on to water – fluctuations of one to two kilos are water, not fat.
A simple check: your urine should be pale yellow. Dark urine, a headache, a dry mouth or tiredness in the afternoon often simply mean: drink a glass of water.