Water intoxication

Water intoxication is a condition that occurs when a person consumes more water than the body can properly expel. Water intoxication can be caused by drinking large quantities of water in a short time or an underlying medical condition that disrupts the work of the kidneys in ridding the body of excess water. This alters the balance of electrolytes in the body, especially sodium. Water intoxication is a relatively rare condition, but it can be fatal due to severe hyponatremia affecting brain function.

Background

Water is essential for life. All plants and animals require an appropriate amount of water to survive and thrive. More than half of the human body is made of water. Digestive fluids, blood, and soft tissue in the body include large amounts of water. This water dissolves and carries nutrients; helps carry out waste products through sweat, urine, and feces; creates a cushion around vital organs; lubricates joints and sensitive tissues such as the eyes and the inside of the nose and mouth; and helps regulate body temperature. Water performs a similar function in all animal life as well.

As a result, people need an appropriate amount of water on a regular basis to survive. This amount is generally considered to be about 3.7 liters or 15.5 cups per day for adult males and 2.7 liters or 11.5 cups per day for adult females, representing total water intake from beverages and food, though other factors such as body size, temperature, health, pregnancy, and activity level can cause a person to require more or less water. This water can be consumed by drinking water or other liquids and also derived from food.

Without enough water, a person will become dehydrated, which can cause symptoms such as excessive thirst, dry mouth, little or very dark urine, fatigue, and confusion. A person may also experience heatstroke, seizures, kidney and liver problems, and in serious cases, a life-threatening drop in blood volume called hypovolemic shock.

Overview

Water is necessary for life, but it is also possible to drink too much water. When the body cannot expel water fast enough, the quantity of electrolytes in the body becomes diluted. Electrolytes are minerals dissolved in fluids, such as those found in the body. They include bicarbonate, calcium, chloride, magnesium, phosphate, potassium, and sodium. These electrolytes carry a positive or negative charge, and these charges are essential to nerve function and muscle contractions. While all the electrolytes are important and necessary, sodium is the most critical.

When a person drinks too much water in a short time, the body’s sodium level drops. The normal sodium level in the blood is 135 to 145 milliequivalents per liter (mEq/L). When this level drops below 135 mEq/L, the resulting condition is called hyponatremia. This drop in sodium level triggers a reaction that causes bodily fluids to move into cells. The cells swell as a result, causing pressure from inside the body. This can cause a host of symptoms, ranging from headaches, nausea, and vomiting to double vision, problems breathing, muscle weakness and cramping, increased blood pressure, drowsiness, and confusion. If excessive swelling occurs in the brain—a condition known as cerebral edema—the person could experience seizures, coma, brain damage, and death.

Water intoxication can occur when a person drinks more than one liter of water, or about 27 to 33 ounces per hour, depending on individual kidney function and physiological conditions. This is the maximum amount the kidneys can process and excrete. When a person consumes more water than this, it remains in the body, leading to fluid accumulation in cells and altering the body’s sodium level. This results in water intoxication.

While rare in the general population, the condition is known to occur more often in some populations. Athletes, especially those participating in endurance events such as marathons, may consume too much water during or after an event. It is estimated that 13 to 15 percent of these endurance athletes will be affected by some form of water intoxication. Military personnel participating in training exercises may also consume too much water too quickly after intense effort. Thirst drives these individuals to drink more water than the body is able to process.

Due to their small size, infants and young children are also more prone to water intoxication. Because of this, physicians do not recommend giving water to children under the age of one. Infants can get all the water they need from milk or formula that provides nutrition and is less likely to be consumed in large quantities. This is also one of the reasons why some physicians advise against swimming classes for infants, especially those that require them to put their faces in the water. The child may ingest too much water and become susceptible to water intoxication.

The early stages of water intoxication can be difficult to detect because the symptoms are similar to other conditions that the person may be experiencing. For example, people who have just run a marathon may be tired, experience muscle fatigue and cramping, and may even vomit. This is a sign of the exertion they have just put forth in the race. They may be encouraged to drink more water. However, if it becomes clear that a runner has consumed a large amount of water and is experiencing these symptoms, they may have water intoxication and need medical care. Without this, the runner’s condition could progress to brain swelling, resulting in seizures and potentially even coma.

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