Introduction
Basically it is important to drink enough every day. 1.5 liters per day are recommended by the German Society for Nutrition. In the case of sporting activities, it should be up to three liters.
If one drinks more than is needed, the body excretes the excess water. However, if you drink extremely large quantities of water that exceed the body’s capacity, dangerous health problems can occur. A so-called water poisoning can ultimately lead to death. People with certain illnesses such as heart or kidney weakness reach a critical limit more quickly and, depending on their severity, may only drink a limited amount per day.
Consequences
The body can regulate its water balance up to a certain amount and excrete excess water mainly through the kidneys. If these regulatory mechanisms are overloaded, too much water remains in the blood. Beverages such as fruit juice spritzers and sports drinks are similar to the blood in the number of dissolved particles in the form of minerals and are then called isotonic.
In contrast, water contains fewer dissolved particles than blood. It is therefore called hypotonic. Drinking large quantities of hypotonic water leads to a dilution of the blood so that the concentration of minerals such as sodium decreases.
However, constant mineral concentrations are important for normal body function. If these are not reached, the first symptoms are muscle weakness, concentration disorders and orientation problems. Other possible symptoms are nausea and headaches.
In addition, there can be seizures and other disturbances of the nervous system up to coma and finally death. A disturbed mineral balance also has dangerous effects on the heart. It can lead to cardiac arrhythmia, which often also ends fatally.
As a further consequence of the lowered concentration of dissolved substances in the blood, more water flows into the cells, since there are more dissolved particles there than outside. Due to a physical principle known as osmosis, water strives to balance the concentration. Consequently, more water penetrates the cells and causes them to swell.
This hinders them in their function or can even destroy them. In addition, water retention (oedema) occurs in the tissue and organs. Brain edema is particularly serious.
But edema can also occur in the lungs and thus hinder breathing. Paradoxically, if the body absorbs too much water, it stops excreting water via the kidneys. Water can never be excreted in the form of urine alone but only in combination with salt.
Since the body is signalled a lack of salt by the low concentration of minerals, it tries to save salt. However, this only increases the problem of overhydration. A vicious circle can arise because the body also signals thirst due to the lack of minerals.
Where the critical limit of a too high water intake is, cannot be said in general and is individually very different. Even if a healthy body can compensate for an intake of up to 10 liters spread over the day by correspondingly large urine excretion, no more than 3 liters should be drunk, as long as one is not exposed to extreme physical stress or heat. Caution is advised in case of reduced kidney function.
Depending on the degree of severity, only very little should be drunk. Likewise, patients with a weakened pumping function of the heart (heart failure) should not drink too much in order not to strain the circulation excessively. In general, it is recommended that you listen to your body and drink when you are thirsty.
In contrast to some animals, humans are not capable of drinking and storing water supplies. The recommended drinking quantity of about 1.5 liters should therefore be spread over the day. However, this is only a guideline value of the German Society for Nutrition.
All articles in this series:
