Do not drink more than one glass of water every 20 minutes and do not exceed one liter per hour.

This limit keeps the electrolytes in the body, namely sodium, potassium, calcium and magnesium, at an optimal level. There is a so-called water intoxication, which occurs in chronic patients taking diuretics and in amateur or professional athletes. This condition can have serious effects.

Excessive hydration can directly bring diabetics and heart patients to the hospital, with symptoms mimicking a heart attack. It recently happened to a doctor, a cardiac patient under treatment.

Dr. Ciprian Constantin, specialist in diabetes, nutrition and metabolic diseases: "He didn't know where he was, didn't know what day it was and had motor deficits, similar to a stroke. It was, in fact, severe hyponatremia, as a result of water intoxication. Patients on diuretics eliminate a lot of salts and replace these electrolyte losses with tap water".

For normal metabolic processes to occur, it is mandatory for blood sodium to be above 130 units. This means drinking a glass of water every 20 minutes, and an extra half-liter during a heatwave. When the maximum amount is exceeded, it's as if we're "drowning" our kidneys. Sodium concentration plummets, the kidneys can't handle it anymore and water intoxication occurs.

In general, the body's hydration needs are linked to its caloric intake. If you need 2,000 calories in 24 hours to neither gain nor lose weight, you need about 2,000 ml of water, or 2 liters a day, to prevent dehydration without saturating your body with water. Values increase for competitive athletes and those who frequent gyms. After a long-lasting workout, it's possible to drink more than a liter per hour, as the kidneys of an average-sized adult can filter.

In young people without chronic illnesses, the first signs are painful muscle cramps.

Monica Iagăr, European champion: "I tell them, 'Take a two-liter bottle, you see it, it's big, it's hefty... you don't need to share it, just drink it as it is, sip by sip, so you can drink two liters". High-performance athletes also take electrolytes with their water. Because, indeed, natural water, in its natural state, does not contain the necessary amount of sodium".

In severe cases, water will move from the intracellular space, where it circulates freely, inside the cells. They increase in volume. But the most dangerous stage is the following: nerve cells swell so much that the brain enlarges like a sponge and presses against the cranial vault. This condition is called hydrocephalus. In the last stage, herniation occurs, meaning the rupture of the brainstem. Brainstem stroke causes deep coma.

An American study shows that among participants in long-lasting sports competitions, such as marathons and cycling races, about 13% experience symptoms of water intoxication. One in 500 cases ends in the athlete's death.