We all know that drinking enough water is essential for good health. But ingesting too much water too fast can be harmful and even deadly. Really! Excessive water disturbs your electrolytes, and importantly reduces your blood levels of sodium (the fancy word for this is dilutional hyponatremia). Mental confusion, drowsiness, and seizures are associated with this as water moves into the brain cells. Severe water intoxication can lead to brain edema, swelling, and death, and occurs most often when excessive amounts are ingested over a relatively short period of time. But this condition has sometimes been reported after drinking too much water over longer periods of time as well. Factors other than the amount of water and frequency of intake are also important. For example, most documented cases of water intoxication involve a combination of excessive water intake and increased secretion of a hormone (antidiuretic hormone, aka vasopressin) that causes your kidneys to conserve water. Vasopressin secretion increases during periods of intense exercise or other physical stress. It has been reported in athletes during periods of physical stress when they drink too much pure water without electrolytes. (Ahh,… This is why our high school coaches were always giving us salt tablets!) Dehydrated young children are also susceptible if they are rapidly rehydrated with pure water only by well-meaning adults.
Water intoxication (dilutional hyponatremia)
Two short articles and a National Institutes of Health website that explain more about how water intoxication occurs. Other less common underlying conditions and causes are also discussed, including polydipsia (excessive drinking as a result of thirst) with some cases of diabetes, mental illness (psycogenic), and dry mouth that can be associated with some medications.
Basic anatomy, physiology and cell biology reviews that help with understanding water toxicity
Videos explaining neurons, the cells in the brain that are most harmed by water intoxication and basics of kidney function (Khan Academy)
More detail about a cell’s requirement for maintaining proper salt (sodium) balance (sparticl.org, click on ‘cells’) and how this is controlled by the kidneys in the human body (sparticl.org, click on ‘excretory system’).
Different types of hyponatremia, dilutional (aka water intoxication) being only one.
Part of a MedCram Lecture Series, this 4-pt series titled Hyponatremia Explained Easily! Consists of four videos providing much greater detail that explain other ways in which how hyponatremia occurs (i.e., other than overconsumption of water over a short period of time) and also how to diagnose and treat different types. These videos are geared toward medical professionals, but others may find the short Part 4 a helpful summary. 15:47 – Part 1; 19:18 – Part 2; 17:45 – Part 3; 6:09 – Part 4
Related topics: Basics of Dose and Exposure, All Natural! All Safe? – Everything is a Chemical, Hazard vs. Risk
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