Why does sodium-heavy liquids like pickle juice, chicken noodle soup, or saline hydrate you better than regular water when you’re dehydrated, but salt water dehydrates you?
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Salt water has about ten times as much salt (35g/l) in it than pickle juice or chicken stock (3.5g/l) and about 40 times as much salt as blood (0.9g/l). The human body goes to great lengths to make sure that its blood always has about the same amount of salt per liter because things start to go wrong if it’s off by too much.
A shot glass of sea water has more salt in it than a whole liter of what the body would actually like. A cup/quarter liter has more salt in it than you need in a whole day. The body can’t properly work with this much salt. And it has only a few options available to get rid of it:
* Sweating: This is the body’s preferred way to get rid of salt and it can do up to about 1.5g of salt per liter of sweat. The body would need to sweat out about 22 times as much water than you just drank to get rid of all that excess salt. So one shot glass of sea water would set you back almost a liter of water via sweat. A cup would set you back about 5.25 liters.
* Urine: urine can theoretically go up to around 15g/l of salt. That would still require at least twice as much water than you just drank to get rid of the excess salt. But these are theoretical maximum values. More likely you’re looking at a lot more.
* Vomiting: this is the emergency “return to sender” option. It get’s rid of all the salt water but also also the rest of your stomach contents which is a good bit of water that it now needs to replace.
No matter how you slice it, it’s a very bad outcome for the body.
Now let’s compare that to drinking too much chicken stock or pickle juice. Let’s say that you somehow drink an entire liter of pickle juice. If the body needed to get rid of all that salt that that would set you back about 1.3 liters via sweating. Via urine the body could possibly do it with a little less than a liter but let’s call it a draw.
How about isotonic drinks like Gatorade. These actually have less salt in them than the body needs on average. If you exercised a lot and only drank these you’d be giving the body more water than salt. One way the body can deal with this is reducing the amount of salt in your sweat as you continued to exercise. Sweat doesn’t need salt to cool you so the body can to some degree make less salty sweat to tweak the ratio of what if keeps in the body. Also you’re probably going to eat something eventually, which will provide more salt than water. So isotinoc beverages are a decent compromise between no salt or potentially too much salt.
What about water? Water has almost no salt in it. So if you drink a lot of water the salt in the body gets spread out more and is harder to use. To a degree the body can still use sweat, urine and vomiting to try and get rid of a good chunk of water but not without sacrificing *some* amount of salt along with it. Creating the opposite problem from drinking salt water. People have actually died from this but it’s very rare. Usually in water drinking contests.
So what do hospitals do when you come in dehydrated? An infusion of 0.9g/l salt water. regardless of what the ratio was in your body it will be mixed and mixed with the ideal ratio until you have both enough water and a good ratio of salt too.
**TL;DR It’s not that more salt is better than less salt. The *correct* amount of salt is better than an incorrect amount of salt.**
Final footnote: Salt is not the only electrolyte that needs to be balanced this way but it is the one we need most of and as such is generally the first one to go wrong.
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