How much water is deadly

Can you die if you drink too much water?

In 2007, the Californian radio station KDND organized a drinking competition: Hold Your Wee for a Wii. Whoever manages to drink the largest amount of water during the four-hour morning show and keep it with them wins a game console. Jennifer Strange, 28 years old and mother of three, wants to get the main prize for her son. Neither she nor her nearly 20 competitors, with whom she competes in the studio, really know what they are getting into. After a short time, the first sufferers from nausea, headaches and dizziness - typical symptoms of hypotonic overhydration, water poisoning. Meanwhile, the station repeatedly receives calls from concerned listeners warning of the fatal consequences of extreme water consumption. A pediatric nurse even reports twice: If you don't stop drinking, you should at least give the participants salt to prevent the worst.

The worst? Dying from too much water? The responsible editors do not take the warnings seriously. Half an hour before the end of the program, Jennifer complains of a severe headache. At this point there is only one other person in the race besides her - all other participants have already voluntarily retired. Jennifer has drunk about 7.5 liters of water in the last three and a half hours. The moderators joke that her water-filled stomach gives the impression that she is pregnant. Jennifer gives up. A few hours later she is dead.

Most fatal water poisoning occurs in connection with drinking competitions, substance abuse, or endurance sports. Accidentally drinking a lot of water, which is life threatening, is extremely rare under normal circumstances. Our body protects itself against flooding by the kidneys quickly excreting excess water. In a healthy adult, the body can relieve itself by around 800 to 1000 milliliters of water per hour.

But how much water is too much?

The amount that is fatal depends on the physical constitution and varies from person to person. Anyone who takes in more water than he has lost and can excrete it through the kidneys messes up his water-electrolyte balance. There is a dilution effect in the blood: the water content increases, which at the same time reduces the salt concentration. Hyponatremia is the name given to the reduced concentration of salts, more precisely sodium, in the blood. In the surrounding tissue, however, the sodium concentration remains the same. The water now wants to compensate for this difference and flows into the cells of the surrounding organs and tissues. Due to the inflowing water, the cells swell or even burst - depending on the concentration gradient, capacity and environment. The heart can lose its rhythm and the lungs fill with water. In response to the reduced salt concentration in the body, the kidneys go on strike: no urine, no loss of salt! The cells in the brain tissue also fill with water. The flooding is particularly critical for the brain because the skull leaves no room to expand. The swelling, a cerebral edema, causes headaches and can cause dizziness, vomiting and convulsions - in severe cases it can lead to a coma or even death.

If you drink a corresponding amount of a liquid that contains sufficient mineral salts instead of water, the water-electrolyte balance remains in balance. Nine grams of salt per liter of water roughly correspond to the body's own concentration. In addition to salted water, apple juice spritzer or beer also meet the electrolyte standard. The latter has other disadvantages - especially in larger quantities - but it does not easily lead to water poisoning.