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
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.
Latest Answers