In case you were wandering: the science behind why drinking seawater dehydrates us.

Discussion in 'Finding, Purifying, and Storing Water' started by Correy, Jun 5, 2016.

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  1. Correy

    Correy Expert Member

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    A cute video on the science of why we shouldn't drink seawater. I think most of us here already know that drinking seawater is a bad idea, but another feature of the video shows us something else that we forget: de-ionised water, or pure water*.
    I wanted to post something about renal function, but I wanted something to be approchable and enjoyable by everyone.
    The video explains the science behind this phenomenon through osmosis. No formulas and math involved.

    *Contrary to what you might think, de-ionised or distilled water can also dehydrate you, but in the complete opposite way than seawater. Drinkable water needs to have a salinity close to the salinity in our blood and tissue fluids, which is around 0.9% salt in water (or for those who might like chemistry, roughly 300mOsm).

    Up to a certain point of salinity our kidneys can handle drinks that are either less dense or more dense in salt, but deviating too much from that 0.9 percentage causes the kidney's mechanism to lose control of the regulation of bodily ions (called osmoregulation). Note that typical sea water (like the oceans) has 3% salt or 1200mOsm , which is about 3 times higher than the salinity our kidneys can handle...and distilled water contains close to zero % of salt.

    Lisa likes this.
  2. FuZyOn

    FuZyOn Expert Member

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    Seawater is definitely bad but I guess if you don't have any alternatives is the best thing you can drink. I've read stories about people surviving even years drinking saltwater so I guess you could still survive (not without a lot of kidney damage though). I didn't know saltwater deviated so much from normal water hwen it comes to salinity percentage.
  3. Correy

    Correy Expert Member

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    If you're lucky enough that you're stranded somewhere where the seas is slightly less salinated, then you could definitely survive one it. Not every seashore has the same percentage of salt. Problem is to test the salitiny you need make some not-so-easy tests or have a device that measures salt in water solutions, otherwise it's kind of a gamble to drink it.
  4. lonewolf

    lonewolf Legendary Survivalist Staff Member

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    I don't think i'd want to even try to survive on seawater, even the taste is disgusting. maybe we could boil the sea water, and collect the steam vapour, that then would be drinkable, I've seen Ray Mears do it but he had all the equipment to be able to do it.
  5. Lisa

    Lisa Active Member

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    Good video, easy to follow and understand. It's never a good idea to drink sea water, even if the salinity of it is less than in other areas it will still contain a higher concentration of salt than that of the fluid in your body and therefore osmosis will be taking the water out of your cells to equal it out and you will become dehydrated quicker than if you didn't drink anything. Always look for another source.
  6. OursIsTheFury

    OursIsTheFury Expert Member

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    Yes, and it is a rather ironic turn of events when you are stranded in the middle of the ocean, as your greatest threat is dehydration and heat, even though you are surrounded by water as far as the eye can see. It's pure torture, and a pretty poetic one, that the most water you can find in this world isn't even drinkable, and would often lead to a quicker death for those who are desperate enough to drink them when they are stranded out there in the middle of the sea. Same thing goes for people in deserted islands, there are plenty of open space filled with water, but you can't even touch it.
  7. Endure

    Endure Expert Member

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    Remember that drinking fresh water is not the only way to get hydration, non dried up food also contains a % of water, not enough to shut down your thirst but It certainly helps. By the way, in case you're wondering about salt concentration in food when we consume salt as part of our daily diets, we usually also drink liquids, which help to dilute the salt and keep it at a healthy level.

    Human kidneys can only make urine that is less salty than salt water. Therefore, to get rid of all the excess salt taken in by drinking seawater, you have to urinate more water than you drank. Eventually, you die of dehydration even as you become thirstier.
  8. joshposh

    joshposh Expert Member

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    I do know of a few native folks, and for the better half of their lives they did live off of brackish water. There was no science back in those days. It was time tested and proven risk that they took. I tend to not worry when I watch these type of videos when there is no clear answer and only more questions and worries.

    The bottom line is, our previous generations had methods that saved their lives and or prolonged it. They best way to figuring things out is to follow what has worked and listen to your body, as it will tell you that something is wrong. If you drink heavy salted water and you feel sick afterwards, then it's best if you don't do that again.
  9. barbecueIt

    barbecueIt New Member

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    This is an enlightening video about seawater. Yes I already know that drinking seawater is not good but the science explanation of it is really great. It was a great mystery to me as kid why drinking saltwater is not being practiced when it's liquid just the same! Currently, some organization is working desalination of seawater, I hope it will be a successful endeavor!
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