The science of saline – why can we drink pure water, but when we put water into our bodies in other ways, like an IV, must we add minerals to it?
In: 480
Same reason you can drink pure water just fine, but somehow your body throws a hissy fit if you fill up your lungs with it.
Our body is basically a donut and our digestive system is the hole. For something to be “in” our body it must leave the digestive system where it then gets everything it needs to function properly within our bodies. If something is given via IV, it is put directly in to our donut bodies and must already contain everything it needs to function within our little donut selves.
…wait. why can’t we drink seawater, again? (Let’s leave all the fish poop and microplastics and whatever the hell all else is in there unless it’s more relevant than I thought)
Chemist here, the pure water you are talking about is a commercial farce meant to sell under the guise that it is cleaner. If you were to drink actual “Pure” water, that being a jug of just water molecules and nothing else, it would be horrible as it would strip your body of all those lovely minerals and nutrients as it doesn’t like to exist in that pure state. It is an amazing solvent.
For saline, it is a specific salt concentration to more closely match blood and it is sterilized so there is a lower chance for infection.
I am not so sure any of the top comments actually answered your question, honestly.
So most of them mention tonicity or osmosis and how pure water can make your cells burst and make you die. All that is true but doesn’t really answer why you can drink pure water (and for all intents and purposes tap water is pure because it’s far from isotonic).
The reason is that when you drink it, your body can regulate how much it takes up and it will also take up salts from the foods you eat and your kidneys will then measure the concentration of salts in your blood and make sure the concentrations stay about the same, because otherwise you will die (keeping everything about the same is called homeostasis). That’s why when you eat lots of salty things you will feel thirsty, and when you drink lots of water without any salty things you will pee a lot (and usually your pee will then be less salty).
You CAN also die from drinking too much water, but you’d have to drink many liters in a short amount of time without having any food in your stomach. This actually happens. Sometimes because of stupid bets but often it happens to athletes like long distance runners if they keep sweating out salts and water and drink lots of water but no salts (hyponatremia). That’s why when you do sports in particular, isotonic drinks are important.
When you get an IV with salt-less water it will just make your blood too dilute too quickly so your body doesn’t really have time to regulate itself.
EDIT: spelling
Your assumption is not correct: you cannot drink pure water. You need some sort of minerals in your water. That can come from food or, better, a little bit in the water and much more from the food.
Imo the real ili5 explanation:
When you drink a beverage your body decides whether or not to add the water content to your bloodstream. This decision is made by at testing sites in your kidneys that see how salty your blood is. If your blood isn’t very salty, it will generally not add much water to your bloodstream, because it has enough.
If you’re putting pure water in your bloodstream, you’re totally bypassing the step of your body deciding if it wants it, and cells don’t like when you have too much water in your blood.
You rarely encounter “Pure Water”, and drinking it will be bad for you.
If you go to the grocery store and buy distilled water and then switch some of it around in your mouth will experience a burning sensation. The living cells of your mouth will absorb the water and pop because they can’t come into balance with it in terms of various pressures.
One of the most common ways you might experience this in normal life is taking any kind of laxative. Laxatives are generally just salt mixed with something to make it palatable. When the salt, which is basically a brine or becomes a brine in your stomach, enters your intestines physics takes over. Physics wants The concentrations of water and salt to be the same on both sides of any permeable membrane. So while some salt will go into your bloodstream and such, much more water will leave your bloodstream and enter your intestines. And that’s why you can suddenly and desperately need to poop.
Normal water has a lot of dissolved ions in it, and by ions we mean dissolve minerals, dissolve metals and all sorts of salts.
If you Add relatively pure water. Your body will have to get rid of it to recover the balances. So it will push a whole bunch of water into your intestines or whatnot or out through your kidneys, and then with that pure water on the other side, it will try to draw the salt out of your body as well.
Basically you can rinse somebody to death by putting pure water into their bloodstream .
So we learned to use “normal saline” which has the same saltiness as your blood, So it won’t flush things in or out of your bloodstream .
But we really should use most of the time is a solution called “lactated ringers” (et al) which is a mixture of four or five salts. Since it balances all those salts and not just the sodium chloride content of your blood. It actually leads to much better medical outcomes. But it’s also way more expensive .
Now if you were not alive, these processes would be very dominant at the concentrations you normally experience. Like you would need to be in way salty or conditions, much like saltwater fish. But one of the things that sells do is pump. So cells can maintain an incline between what’s in your digestive tract, what’s inside of the individual cells, and what’s inside of your bloodstream.
Basically as long as what you’re putting in your body is close enough It will do fine, but the closer the better.
This is also why you can’t drink seawater, white saltwater fish can’t live in freshwater, and my most freshwater fish can’t live in saltwater, and why some plants can and some plants can’t and some can do both.
Life thwarts simple physics by applying much more complex physics.
can we start by addressing that while you can drink pure water you shouldn’t. pure water will strip the body of minerals. drink enough and you will die and not from hydrotoxicity.
Food. It’s all about food. If you drank enough pure water you would in fact die. Your food has all the mineral you need normally.
For an interesting example of when this gets scary, Gorillas were observed eating rotten wood. It was determined that they were getting a substantial amount of potasium IIRC or sodium ? from the punky rotten wood. It turns out a vegetarian diet in the rain forest can be quite poor in minerals.
The reason they add salt to fluids added directly into the blood is to try and match the concentration of the blood. You could add pure water to the veins very very slowly and you’d probably still be ok. But people have died from being given large amounts of pure water by accident into a vein.
Latest Answers