What is water intoxication? How much excess water is harmful?

All cells and organs in our body need enough water to function properly. Water lost through sweat, urine and breathing must be replaced. Inadequate water consumption causes fatigue, dizziness and muscle cramps. However, excessive water consumption can also cause a serious condition called water intoxication to develop.

What is water intoxication?

Water intoxication is impaired brain function resulting from excessive water consumption. Excessive consumption increases the amount of water in the blood, reducing the concentration of electrolytes, especially sodium. When blood sodium levels fall below 135 mm/L, this condition is called hyponatremia (low blood sodium level) and below 130 mm/L, symptoms of hyponatremia such as nausea, weakness, headache and irregular blood pressure begin to appear.

Sodium is the most important electrolyte maintaining fluid balance inside and outside cells. When its concentration in the blood falls, fluid moves into cells and they swell. When this happens in brain cells, it can cause potentially life-threatening effects.

Drinking too much water can be dangerous!

When brain cells swell, pressure inside the skull increases. Increased intracranial pressure manifests through symptoms such as headache, nausea and vomiting. Severe cases may involve more serious symptoms: increased blood pressure, dizziness, double vision, lethargy, difficulty breathing, muscle weakness and cramps, and difficulty perceiving sensations. Excess fluid accumulation in the brain (edema) may also affect the brainstem and impair central nervous system function. Consequently, water intoxication can cause seizures, brain damage, coma and even death.

How much water is too much?

Water intoxication from excessive consumption occurs when more water is drunk than the kidneys can excrete through urine. However, the amount is not the only important factor; how quickly we consume it also matters. Drinking too much water in a short time is the main risk factor.

The kidneys can excrete at most 20 liters of water daily through urine, meaning they cannot excrete more than an average of 0,8-1,0 liters per hour. Hyponatremia symptoms may occur after drinking 3-4 liters of water in a short time.

Water intoxication caused loss of life!

Accidentally consuming excessive water is very difficult, but many cases have been reported among American soldiersin service. One report described sodium levels of 115-130 mm/L in 17 soldiers who developed hyponatremia after excessive water consumption (normal blood sodium is 135-145 mm/L). Another report stated that three soldiers died from hyponatremia and brain edema. These deaths were reported to result from drinking 10-20 liters within a few hours.

Water intoxication endurance sports participants can also experience it. Excessive water consumption during these activities is considered a solution to dehydration . Hyponatremia can therefore also occur frequently at major sporting events. After a marathon, a runner's sodium was found below 130 mm/L; excessive fluid accumulated in the brain and brainstem herniation developed, resulting in death.

Excessive water consumption can also occur in psychiatric patients, particularly those with schizophrenia . A study examining 27 people with schizophrenia who died young found that five had died from self-induced water intoxication.

How much water do we actually need?

The amount of water needed daily varies from person to person, and an exact quantity is difficult to specify. Body weight, physical activity level and climate should be considered in determining needs. Guidelines state that adequate daily water intake should be limited to 3.7 liters for men and 2.7 liters for women. However, these recommendations include total daily fluid intake, including water in drinks and foods.

Some people still follow the rule of 8 glasses of water daily. This rule is largely arbitrary and not research-based.

The best current rule is to listen to the body and drink when thirsty. However, this may not work for everyone. Athletes, older people and pregnant women should consume extra water every day.