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Alas, this article is not remotely accurate. In truth, the best thing that you can drink when extremely dehydrated is lightly salted, sugared water (on an empt

by jforman 15y ago

Alas, this article is not remotely accurate. In truth, the best thing that you can drink when extremely dehydrated is lightly salted, sugared water (on an empty stomach, at least — food can provide the salt/sugar otherwise). This is why Pedialyte, which contains both salt and glucose, is often given to dehydrated children and adults. This is also why Gatorade is better than pure water. The reason for this is that water absorption in your small intestines is significantly more complicated than depicted in the image in this article. Water is not absorbed across a simple membrane passively — rather, the small intestine is a two-layer barrier with specific transport proteins positioned in each layer of the barrier in order to pull nutrients into the body at a very high efficiency. A dominant theory right now is that sodium-glucose co-transporters are responsible for drawing water into the body (see http://www.ncbi.nlm.nih.gov/pubmed/16322051 http://www.ncbi.nlm.nih.gov/pubmed/16322051 and http://en.wikipedia.org/wiki/Sodium-glucose_transport_proteins http://en.wikipedia.org/wiki/Sodium-glucose_transport_protei...). Specifically, an osmotic gradient is created by (I think) the Na/K active pump ("active" meaning the body uses up ATP to overcome the normal steady state). The Na/glucose co-transporter then uses this gradient to pull those molecules into the body, bringing water with it — the water of hydration. If we were hydrated using a simple system such as the one depicted in the link, we would be orders of magnitude more responsive to the food we eat. Our bodies are very good at maintaining homeostasis, but it takes a lot of complexity to do it. Edit: it's worth noting that seawater may indeed be too highly concentrated to drink safely, even in moderate quantities, if it's true that the kidney cannot excrete at a greater concentration of salt as is present in seawater. This link from Wikipedia suggests this is the case: http://www.newton.dep.anl.gov/askasci/bio99/bio99416.htm http://www.newton.dep.anl.gov/askasci/bio99/bio99416.htm . But the posted article's explanation is entirely off-base in its explanation regardless. And I'm not even sure what of seawater would be absorbed on an empty stomach...it's possible more salt than water would be absorbed, leading to diarrhea as water is left unabsorbed in the intestine, leading to dehydration from poor water absorption and poor salt excretion.

icegreentea 15y ago
Well, to be fair they are talking about sea water, which has an approximate average salinity of 35g/L [1]. Gatorade (reading off the label from the bottle sitting on my desk) has 110mg of sodium and 30mg of potassium per 240mL, so about 600mg of 'salt' per liter. There's ~60 times more salt in sea water than Gatorade. We are actually pretty good at maintaining homeostatis. But it's really hard to deal with the amount of salt in sea water. In addition, you and the article are not actually going over the same thing. The stated problem is not during absorption (which you deal with), but what happens after you absorb the salt water. [1] http://en.wikipedia.org/wiki/Seawater http://en.wikipedia.org/wiki/Seawater
- jforman 15y ago
  "The stated problem is... what happens after you absorb the salt water" — other comments about this paragraph notwithstanding, it's just not true that simple osmosis from blood to cells is the operative factor in hydration, so the article is totally off-base. You can't talk about hydration without talking about intestinal absorption and concentration of urine in the kidneys.
todsul 15y ago
Did you bother reading the article? > Alas, this article is not remotely accurate. I'd like you to qualify this. "Not remotely accurate." Do you suggest sea water is a remedy for dehydration. Or are you suggesting osmosis doesn't occur across cell membranes. Or maybe you're disputing the process of osmosis altogether and the transfer between varying salinities. Which one is it exactly? The article is talking about the dangers of drinking sea water when severely dehydrated if stranded on the coast or at sea. You can't extrapolate the sodium in Gatorade to drinking straight sea water. That's not only haphazard, but completely irresponsible considering we're discussing health and survival. Also, the images depict cells all over the body; not just in the small intestine and certainly not villi. Sure, this isn't the most robust explanation of a bodily function. This is an expedition travel website. It's not the Journal of Medical Science. The purpose of the article is to stop people drinking sea water as a remedy for dehydration. As some people have mentioned, small controlled quantities may help. But when you're that delirious, I can't help but think even having that thought in your mind would cause more harm than good.
- jforman 15y ago
  Yes, I read the article. "Do you suggest sea water is a remedy for dehydration. Or are you suggesting osmosis doesn't occur across cell membranes. Or maybe you're disputing the process of osmosis altogether and the transfer between varying salinities. Which one is it exactly?" I just mean this: whether seawater causes dehydration in small quantities is a complex question, one which reading this article will provide absolutely no insight into. "You can't extrapolate the sodium in Gatorade to drinking straight sea water. That's not only haphazard, but completely irresponsible considering we're discussing health and survival." I never said that seawater is hydrating? Seawater lacks glucose and may have too high a salt concentration to promote hydration even if it did contain glucose. My apologies to anybody who misinterpreted my post after finding themselves stranded on a desert island. "Also, the images depict cells all over the body; not just in the small intestine and certainly not villi." The images are clearly presented in such a way as to suggest that simple osmosis between cells and seawater-containing blood is the operative factor in determining hydration. This is totally untrue. "Sure, this isn't the most robust explanation of a bodily function. This is an expedition travel website. It's not the Journal of Medical Science." That doesn't give them license to just make stuff up.
ahoyhere 15y ago
Lots of people have died from drinking sea water. It's still a Very Bad Idea. Your argument is along the lines of "They got technical details wrong; salt water is sometimes important; therefore the whole thing is wrong." But that is like saying the advice to "Do not handle rattlesnakes" doesn't apply because some folks get a great deal out of handling rattlesnakes. The fact is, people who don't know what they're doing shouldn't handle rattlesnakes… or drink sea water. Now let's talk about oral rehydration salts -- the non-fancy name for the salt water and "glucose transporters" you described. The salinity of Oral Rehydration Salts/Solution is nowhere near as high as sea water -- and without the sugar, saltwater doesn't rehydrate. The formula for making it yourself is about 1/2 tsp salt in a liter of water, plus 6 tsp of sugar. That's a lot of sugar to balance out just a little salt: 1:12 ratio. A quick Google suggests that 35g of salt is what one would expect in a liter of sea water (on average). A tsp of salt weighs 5.7 g. Therefore, the concentration of salt in sea water is 6 teaspoons vs 1/2 tsp in ORS, or 12x the concentration of salt. And no sugar. I drink ORS on a regular basis to deal with one of the side effects of chronic fatigue syndrome: an imbalance of hormones in the body which leads to insufficient electrolytes which leads to POTS (postural orthostatic tachycardia syndrome), dizziness, muscle cramps & twitches, brain fog/inability to think straight, and inability to drink adequate water. ORS has been a total life changer for me -- before, doctors just said I was "too out of shape" when sitting up/standing led to a doubled heart rate, dizziness, the feeling that "the bottom dropped out of my head", near fainting, etc. Because that's a valid explanation when a 27-year-old nearly passes out from standing up. (Not.) Drinking a little salty-sugary solution solves my symptoms in 20 minutes. But I sure as hell wouldn't drink sea water.
- mikeash 15y ago
  The article is titled, "Why Can’t We Drink Sea Water?" The technical details that they got wrong are the whole point of the article, and it is completely reasonable to complain when such an article is inaccurate.
  - djacobs 15y ago
    I agree. No correction would've been necessary if the article had been titled "Don't drink sea water (supported by scientifically inaccurate, but fancy-sounding facts)".
DevX101 15y ago
If I were a professor and the question was "why we can't drink sea water", I'd give the article a higher score than yours. Your comment is about the best method to hydrate oneself. His article is about "why we can't drink seawater".
- ars 15y ago
  It might be about that - but it's wrong. The obvious proof is that Penguins and Fish can drink sea water. At least the comment was correct, although about a somewhat different subject.
  - mekoka 15y ago
    I wouldn't go as far as saying it's wrong, but rather that it's not complete. The article simply focused on osmosis to explain the process of dehydration at a cellular level (blood). In that, I'd say it was rather accurate. Now, if you absolutely want the bigger picture, we could go as far as stipulating that the human renal system (kidneys) have limitations and is unable to excrete salt at seawater's concentrations, which is how dangerous levels of sodium chloride could find their way into the bloodstream, when someone drinks seawater. Penguins can drink seawater because, in addition to kidneys, they have a gland that is very efficient at excreting salt from their body. So efficient, in fact, that the byproduct is a saturated saline solution (which is what you see when a penguin has a "runny nose"). A penguin with a defective supraorbital gland would die of dehydration, like any human, if it drank seawater.
    - jforman 15y ago
      "The article simply focused on osmosis to explain the process of dehydration at a cellular level (blood). In that, I'd say it was rather accurate." Cellular osmosis and dehydration have almost nothing to do with one another. The article is, indeed, wrong, in trying to associate these things with one another.

by jforman 15y ago

icegreentea 15y ago

Well, to be fair they are talking about sea water, which has an approximate average salinity of 35g/L [1]. Gatorade (reading off the label from the bottle sitting on my desk) has 110mg of sodium and 30mg of potassium per 240mL, so about 600mg of 'salt' per liter. There's ~60 times more salt in sea water than Gatorade. We are actually pretty good at maintaining homeostatis. But it's really hard to deal with the amount of salt in sea water. In addition, you and the article are not actually going over the same thing. The stated problem is not during absorption (which you deal with), but what happens after you absorb the salt water. [1] http://en.wikipedia.org/wiki/Seawater http://en.wikipedia.org/wiki/Seawater

jforman 15y ago
"The stated problem is... what happens after you absorb the salt water" — other comments about this paragraph notwithstanding, it's just not true that simple osmosis from blood to cells is the operative factor in hydration, so the article is totally off-base. You can't talk about hydration without talking about intestinal absorption and concentration of urine in the kidneys.

todsul 15y ago

Did you bother reading the article? > Alas, this article is not remotely accurate. I'd like you to qualify this. "Not remotely accurate." Do you suggest sea water is a remedy for dehydration. Or are you suggesting osmosis doesn't occur across cell membranes. Or maybe you're disputing the process of osmosis altogether and the transfer between varying salinities. Which one is it exactly? The article is talking about the dangers of drinking sea water when severely dehydrated if stranded on the coast or at sea. You can't extrapolate the sodium in Gatorade to drinking straight sea water. That's not only haphazard, but completely irresponsible considering we're discussing health and survival. Also, the images depict cells all over the body; not just in the small intestine and certainly not villi. Sure, this isn't the most robust explanation of a bodily function. This is an expedition travel website. It's not the Journal of Medical Science. The purpose of the article is to stop people drinking sea water as a remedy for dehydration. As some people have mentioned, small controlled quantities may help. But when you're that delirious, I can't help but think even having that thought in your mind would cause more harm than good.

jforman 15y ago
Yes, I read the article. "Do you suggest sea water is a remedy for dehydration. Or are you suggesting osmosis doesn't occur across cell membranes. Or maybe you're disputing the process of osmosis altogether and the transfer between varying salinities. Which one is it exactly?" I just mean this: whether seawater causes dehydration in small quantities is a complex question, one which reading this article will provide absolutely no insight into. "You can't extrapolate the sodium in Gatorade to drinking straight sea water. That's not only haphazard, but completely irresponsible considering we're discussing health and survival." I never said that seawater is hydrating? Seawater lacks glucose and may have too high a salt concentration to promote hydration even if it did contain glucose. My apologies to anybody who misinterpreted my post after finding themselves stranded on a desert island. "Also, the images depict cells all over the body; not just in the small intestine and certainly not villi." The images are clearly presented in such a way as to suggest that simple osmosis between cells and seawater-containing blood is the operative factor in determining hydration. This is totally untrue. "Sure, this isn't the most robust explanation of a bodily function. This is an expedition travel website. It's not the Journal of Medical Science." That doesn't give them license to just make stuff up.

ahoyhere 15y ago

Lots of people have died from drinking sea water. It's still a Very Bad Idea. Your argument is along the lines of "They got technical details wrong; salt water is sometimes important; therefore the whole thing is wrong." But that is like saying the advice to "Do not handle rattlesnakes" doesn't apply because some folks get a great deal out of handling rattlesnakes. The fact is, people who don't know what they're doing shouldn't handle rattlesnakes… or drink sea water. Now let's talk about oral rehydration salts -- the non-fancy name for the salt water and "glucose transporters" you described. The salinity of Oral Rehydration Salts/Solution is nowhere near as high as sea water -- and without the sugar, saltwater doesn't rehydrate. The formula for making it yourself is about 1/2 tsp salt in a liter of water, plus 6 tsp of sugar. That's a lot of sugar to balance out just a little salt: 1:12 ratio. A quick Google suggests that 35g of salt is what one would expect in a liter of sea water (on average). A tsp of salt weighs 5.7 g. Therefore, the concentration of salt in sea water is 6 teaspoons vs 1/2 tsp in ORS, or 12x the concentration of salt. And no sugar. I drink ORS on a regular basis to deal with one of the side effects of chronic fatigue syndrome: an imbalance of hormones in the body which leads to insufficient electrolytes which leads to POTS (postural orthostatic tachycardia syndrome), dizziness, muscle cramps & twitches, brain fog/inability to think straight, and inability to drink adequate water. ORS has been a total life changer for me -- before, doctors just said I was "too out of shape" when sitting up/standing led to a doubled heart rate, dizziness, the feeling that "the bottom dropped out of my head", near fainting, etc. Because that's a valid explanation when a 27-year-old nearly passes out from standing up. (Not.) Drinking a little salty-sugary solution solves my symptoms in 20 minutes. But I sure as hell wouldn't drink sea water.

mikeash 15y ago
The article is titled, "Why Can’t We Drink Sea Water?" The technical details that they got wrong are the whole point of the article, and it is completely reasonable to complain when such an article is inaccurate.
- djacobs 15y ago
  I agree. No correction would've been necessary if the article had been titled "Don't drink sea water (supported by scientifically inaccurate, but fancy-sounding facts)".

DevX101 15y ago

If I were a professor and the question was "why we can't drink sea water", I'd give the article a higher score than yours. Your comment is about the best method to hydrate oneself. His article is about "why we can't drink seawater".

ars 15y ago
It might be about that - but it's wrong. The obvious proof is that Penguins and Fish can drink sea water. At least the comment was correct, although about a somewhat different subject.
- mekoka 15y ago
  I wouldn't go as far as saying it's wrong, but rather that it's not complete. The article simply focused on osmosis to explain the process of dehydration at a cellular level (blood). In that, I'd say it was rather accurate. Now, if you absolutely want the bigger picture, we could go as far as stipulating that the human renal system (kidneys) have limitations and is unable to excrete salt at seawater's concentrations, which is how dangerous levels of sodium chloride could find their way into the bloodstream, when someone drinks seawater. Penguins can drink seawater because, in addition to kidneys, they have a gland that is very efficient at excreting salt from their body. So efficient, in fact, that the byproduct is a saturated saline solution (which is what you see when a penguin has a "runny nose"). A penguin with a defective supraorbital gland would die of dehydration, like any human, if it drank seawater.
  - jforman 15y ago
    "The article simply focused on osmosis to explain the process of dehydration at a cellular level (blood). In that, I'd say it was rather accurate." Cellular osmosis and dehydration have almost nothing to do with one another. The article is, indeed, wrong, in trying to associate these things with one another.