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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Basically your body is always trying to find balance which is called homeostasis. Dehydration also usually means low electrolytes so sodium replacement is important.
Also waster follows salt so giving saline basically means you are giving the body both the water it needs and the salt it needs to draw it into the kidneys.
If you want to know more about how this works google the loop of Henle, this is the structure within the kidneys which draws in the sodium and thus the water. Fascinating biology
for those looking for a great re-hydrating drink for when you’re suuuper low on electrolytes: Jumex. I swear that the Mango Jumex (yes I know it is for cooking) has saved my life on more than one occasion.
**ELI5:** Your body needs sodium (and potassium) to hydrate your cells. If you are too low or too high on either of these, you cannot properly hydrate. Period. Generally when you’re dehydrated, you’re low on sodium as well because our sweat contains a lot of sodium. So these sodium rich liquids help because they enable your body to absorb more water. Generally, not always. Saltwater, on the other hand, contains TOO MUCH salt. If you drink saltwater you suddenly have the opposite problem. You have TOO MUCH sodium and your body can once again no longer properly hydrate.
**ELI’ve taken chemistry:** Your body’s cells use something called a sodium potassium pump to regulate the amount of water in your cells. The way this works is that enzymes in your cells will pump an unequal amount of things either inside your cell or outside. I THINK the ratio is like 2-3 or something. So it’ll pump 3 sodiums in your cell but only 2 potassiums out, therefore increasing the charge inside the cell (because both sodium and potassium have a +1 charge). What this means is that your body regulates the amount of sodium and potassium on the inside and outside of your cells. By doing this, your body uses osmosis to hydrate your cells. (Osmosis means that water will ALWAYS flow from an area of low concentration to an area of higher concentration. Don’t believe me? Fill two glasses with tap water. Connect them via a wet paper towel. Put a bunch of salt in one and leave it sit for an hour, watch what happens.) So, if your cells are dehydrated, they’ll pump more charge INSIDE the cell, so that the concentration of ions INSIDE the cell is higher than the concentration outside, so that water, via osmosis, will flow INTO the cell. Therefore you NEED sodium to hydrate. If you are too low on sodium your body cannot physically hydrate. Visa versa for a cell that’s too hydrated.
So, because your body uses this sodium potassium pump in your cell walls, it NEEDS sodium and potassium to properly function. Furthermore, it NEEDS sodium and potassium in a relatively consistent ratio. Anything that’s not close to this ratio is bad. Whether one is too low or too high. Too low sodium is bad. Too high sodium is bad. Too low potassium is bad, too high potassium is bad. (Some of those four are worse than the others though.)
GENERALLY when a human is very, very dehydrated, they’re low on sodium and low on liquids. Drinking a sodium rich drink helps with this. We lose a lot more Na in our sweat than we lose K, so it needs to be replenished more. This is why we often do 1/2 water and 1/2 Gatorade because MOST OF THE TIME, we’re not seriously dehydrated, and we need more liquid than sodium.
Because of how your body absorbs water. Your colon is a very intelligent organ, and avoids absorbing pure water (cause that’d burst your cells). Instead, it absorbs it in a for that’s close to the body’s plasma. This generally means electrolyte impurities, like sodium. So essentially, pure water is not particularly welcome in your body, add some minerals and your body eat that up like a sponge.
PS: If anyone tells you to take more water that you feel your body needs, don’t do it. Too much water can and does damage your kidneys.
On a related note (or would this be fodder for a different ELI5 post), why are sour/acidic liquids (such as lemonade, sodas, switchel/haymaker’s punch, etc) more refreshing than sweeter liquids or plain water? Is it the free protons, or something else?
Salt water has a much higher amount of salt in it than those other things. If you’re dehydrated you probably are low on salt (electrolytes) so a bit of salt is good. But if you take in a lot of salt your body has to flush it out with water through urine which gets rid of the water in your body
“The dose makes the poison” applies here. too much salt will kill you because it’s higher than the amount of salt in your body. too little salt will also kill you because you need a certain amount every day to replace what you lose from sweating and peeing. But usually there’s so much salt in your food that you can just drink plain water to hydrate. But if you drink enough plain water you will in fact die. I’ve seen people try in the hospital.
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