If salt is edible and water is, why is drinking saltwater not good for you? Like sometimes you have to swish warm saltwater around in your mouth and getting ocean water in your mouth is okay so why us drinking it bad?
In: Biology
Our kidneys cannot make urine from a concentration of salts of more than 2%. Seawater is made up of approximately 3% salt, so if we drink it to quench our thirst the kidneys have to use existing water from our body in order to dilute the extra salt, which in turn makes us feel even thirstier.
https://www.google.com/search?q=salt+water+osmosis&rlz=1CDGOYI_enUS899US899&hl=en-US&prmd=sivn&sxsrf=ALeKk02UqXrHNjg-vumtq6qbY7xIr89sdA:1596593136373&source=lnms&tbm=isch&sa=X&ved=2ahUKEwj34vn1_ILrAhWnonIEHUngApgQ_AUoAnoECA0QAg&biw=414&bih=724#imgrc=B-oAO13PEodJmM&imgdii=J3XlDAWaUrKUUM
Here’s a good image to explain if. Salt is in higher concentration in salt water. Water wants to be in a more stable state, called equilibrium, where concentration is equal throughout. So water flows out of your body’s cells, where it is needed, and to the salt water, to achieve equilibrium. Thus, the salt water never gets to your cells, which is why you need to drink water in the first place, and instead removes water from your cells.
The concentration of salt in the water is much higher than that of your blood. So your kidneys would have to remove the salt since they filter stuff like that. In order to filter that, they use water from your body, which in turn, makes you dehydrated rather than hydrated. This is on top of the fact that water moves in areas of high concentration to areas of low concentration (osmosis) and this will remove water from organs and tissues.
Human bodies aren’t designed to be able to drink salt water safely. Our kidneys process the water we drink, and remove excess water or salt in the form of urine. The saltiness of ocean water is much higher than our kidneys can handle, and causes the whole kidney system to stop working right. Drinking much salt water can result in kidney damage. Other animals have different tolerances. For instance marine mammals like whales are obviously able to cope with ingesting salt water just fine. This is the result of adaption. Having kidneys which are capable of handling salt water takes extra energy, so animals which didn’t routinely drink salt water didn’t evolve this capability, because it would have been wasted. We evolved from apes which didn’t spend a lot of time in the ocean (we evolved in the forests and savannas of Africa, far from the ocean).
Taking a small sip of saltwater is no worse for you than eating a little bit of salty food. It’s only bad if you drink more of it. The thing is that it’s so salty that your body loses water when you drink it rather than gaining water, so you can’t use it to supply the water that your body needs to function.
To add to this, the LD50, or median lethal dose, of salt is around [3g/kg of bodyweight in rats](https://whs.rocklinusd.org/documents/Science/Lethal_Dose_Table.pdf). Typically, you can project similar numbers for people. This means that 50% of rats that eat this quantity of Sodium Chloride die. Great odds if you’re talking about free money, terrible odds if you’re talking about potentially dying.
This means that a 150 lb individual (roughly 68kg body weight) would have to eat 204 grams of salt to get something like a potential LD50 lethal dose.
If saltwater is a 3% solution by weight, for every 100ml of salt water you drink, you’d be getting 3g ofsalt.
For every liter (1000ml) you’d be getting 30g of salt. If you drank 4 liters- which is close to a US gallon, you’d be over halfway to the LD50 amount at 120 grams. Two gallons and you’d be over that, and in potentially lethal territory.
Latest Answers