I mean, I’ve heard that you can typically only survive about three days without water, but what exactly causes your body to fail when you dehydrate too much?
I guess one point is lack of salts (if you sweat a lot) but I’m specifically wondering about lack of water (although a closer explanation about how lack of salts will kill you is also appreciated)
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Your bladder and kidneys need water to function. Initially, your kidneys slow sending water to your bladder which is why your pee turns dark. Then you start losing water in your blood to keep organs functioning but the decrease in blood volume causes your blood pressure to drop. This makes pumping blood increasingly difficult for your heart so your body will start sending less blood to your organs. This starts damaging all your organs and eventually your kidneys stop filtering your blood. Toxins build up in your brain that’s already not getting enough blood and eventually shuts down and you die.
As water level decreases, the total amount of sodium stays the same. So, essentially it is increasing in concentration. Too much salt interferes with heart cells’ ability to contract together. So less water = more salt = less heart coordination.
Cardiac arrhythmia due to hypernatremia and hypovolumenia can be fatal. There are many changes that occur, but the effect on the heart will kill ya.
This was the response I got from Perplexity.ai.
The tl;dr is from there, too:
Dehydration can lead to death through mechanisms such as organ failure, blood thickening and reduced blood pressure, electrolyte imbalance, brain swelling, shock, and build-up of cellular waste.
Electrolyte imbalances and upset balance of salts and sugar can cause impaired cellular function, heart problems, neurological issues, kidney damage, and shock, ultimately leading to death.
It is a common misconception that you need salt when you exercise and sweat a lot. You absolutely do not need salt.
That’s a very incorrect statement. NaCl, KCl, and MgCl2 are essential for our bodies to function appropriately. If you are working out for an hour or mowing the lawn on a hot day, you are mostly correct. You can replace the lost salt though a balanced diet. If you have sustained sweating, such as when you run a marathon or play a match of football, it can be deadly to not replace these salts.
In the vast majority of cases, people don’t need salt when they exercise. You just described a fringe case that virtually no one experiences. You high school football coach shouldn’t be giving you salt. That could be dangerous. They should be giving you water.
The coach won’t be giving them salt directly, but will always provide a sports drink which contains salts.
Ever watch any sport and a player falls over with a cramp? They have drunk too much water and not enough electrolytes.
Here’s a study from one hospital in Oslo, Norway. Norway is not considered a hot region of the world. Between 2010 and 2015 they treated 31,000 patients in the ER from a population of 135,000 for electrolyte imbalance. That’s roughly 18 patients a day. This is not some sort of fringe case.
Salts are absolutely necessary for ordinary nerve- and muscular function. If you’ve ever sweated a lot without eating or drinking some salt solution you would notice your muscles start twitching, vibrating and cramping. After a while you can also notice getting light headed and blurry vision.
Source: Been in situations with plenty of water but no salt, and enormous amounts of sweat. Been in the same situations with access to salt for comparison.
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