Can you drink too much water? — Explainer video

Transcript

Can you drink too much water? Why it comes down to speed.

The short answer: yes. But it takes extraordinary amounts. Anyone who drinks normally stays far below that.

If someone drinks considerably more in a short time than the kidneys can process, the blood becomes diluted and the sodium level falls. If it falls markedly, water shifts into the cells, including those of the brain, which can swell as a result. This is colloquially known as “water intoxication”.

The speed of drinking matters more than the daily total. As a rough guide: healthy kidneys can excrete around one litre per hour. Documented cases almost always involve several litres within a few hours.

In healthy adults, thirst is a reliable signal. It makes itself felt long before any meaningful deficit. There is no basis for “detoxing” by drinking a lot.

The risk is best documented in endurance sport. Then there are diseases of the kidneys, heart or liver, medicines that affect the water or salt balance, and pathologically increased drinking. Anyone who is chronically ill or takes medication regularly should discuss how much to drink with their doctor.

Possible warning signs after drinking very large amounts: headaches, light-headedness, nausea and vomiting, confusion, muscle weakness or cramps. Then medical help is needed immediately, but no more water: it makes the problem worse.

For healthy people, a rule of thumb is enough: drink to thirst, have a glass with meals, and moderately more in hot weather or during exercise. Caution is only warranted with extreme amounts in one go.

More on this in the Piz Sardona Academy.