Have you ever drunk your own urine?

[TimberWolf]

Why? The digestive tract uses energy to overcome osmosis... IIRC something like 80% of the water that is excreted at one point is then reabsorbed later, or something like that anyway. Doesn't mean the thing's not a myth for other reasons of course.

True (although I can't speak for your figures). I've mainly been going on what if seen from the best sources I've found plus the intuitive feeling that if this [pumping water up your arse] worked it would be in all survival books and in literature going through the ages. Grylss on the other hand is mostly a twit to be watched for entertainment purposes only.

My basic understanding, from a quick look, is that 'juices' are released into the intestine which increase the osmotic pull of water from capillaries, which makes the intestinal content more watery, which increases digestive efficiency. Later, active transport (the term used for what you describe, which uses energy as you say) is used to pull back in those ions, and this induces water to be absorbed back in to the bloodstream. This whole affair, one might think, would be more or less ion neutral, not including the salts and water absorbed from that ingested. Dealing with excess salt, or saltwater which is more concentrated than the blood, would require a mechanism to remove excess ions absorbed (excess even over that in blood, why do that?). I guess this would be the job of the kidneys, which will also regulate a balance. So if the salt bottleneck weren't at the intestine, it will be at the kidneys. And if so, that would apply wherever the salt is absorbed in the intestine, and we already know seawater dehydrates, i.e human kidneys can't handle that salt concentration. That's my best 'why' for now, but I'd prefer to cite medical or experimental data, rather than stories of someone who happened to survive despite doing things that are more likely to do harm than good or some well known TV nut.

Less dumbed-down description:

Absorption of Products of Digestion
Histology of the Ileum in Relation to its Secretory and Absorptive Functions

* Na+, Cl-, digestive juice secreted into duodenum → LOWERS water potential
* \ H2O moves from epithelial cells into lumen by osmosis
* Increases efficiency of digestion (hydrolytic reactions) and absorption
* Ileum absorbs ions by active transport → INCREASES water potential
* \ H2O moves back into epithelial cells

Digestive System

[minestrone]

from what your missus says, it has to go further up. maybe some sort of tube is required

I was thinking Spod as well.

[EternalOptimist]

TW, i couldnt find any trace on the web relating to the story I read many moons ago, but I did find this



We put this to Miles Parks, Gastroenterologist, and Ari Ercole, Intensivist, both from Addenbrookes Hospital...

Miles - Using the rectum as a means of administering fluid replacement in dehydrated individuals is an interesting idea. The colon or large bowel functions primarily to absorb fluid, normally doing so of course as material enters to the cecum from the small intestine, the material which has not been digested, fibrous products and so on, together with a substantial amount of fluid and solute enters into the colon, and the fluid is then sucked out as the material goes around the 4 feet or so of the colon to form up the stool. And so, you can see the colon is well designed for absorbing liquid but it really needs to do so in the context also of transport of solutes, that’s to say of sodium and chloride ions, and so on. It’s the absorption of these, of the solute itself which then creates the osmotic gradient which sucks fluid across the lining of the bowel, and into the bloodstream. So, bearing these things in mind, I do think that water enemas on their own or water on its own is perhaps unlikely to be absorbed in a clinically significant quantities, and of course, it’s just likely to come out of the rectum again whereas, I think administering saline or something of that type would potentially lead to quite a significant absorption of fluid.

Diana - Water on its own probably wouldn’t do very much, but a saline solution could give one a better chance of a drink. But what if you're stuck for saline drips and all you've got is a much saltier seawater?

[TimberWolf]

TW, i couldnt find any trace on the web relating to the story I read many moons ago, but I did find this



We put this to Miles Parks, Gastroenterologist, and Ari Ercole, Intensivist, both from Addenbrookes Hospital...

Miles - Using the rectum as a means of administering fluid replacement in dehydrated individuals is an interesting idea. The colon or large bowel functions primarily to absorb fluid, normally doing so of course as material enters to the cecum from the small intestine, the material which has not been digested, fibrous products and so on, together with a substantial amount of fluid and solute enters into the colon, and the fluid is then sucked out as the material goes around the 4 feet or so of the colon to form up the stool. And so, you can see the colon is well designed for absorbing liquid but it really needs to do so in the context also of transport of solutes, that’s to say of sodium and chloride ions, and so on. It’s the absorption of these, of the solute itself which then creates the osmotic gradient which sucks fluid across the lining of the bowel, and into the bloodstream. So, bearing these things in mind, I do think that water enemas on their own or water on its own is perhaps unlikely to be absorbed in a clinically significant quantities, and of course, it’s just likely to come out of the rectum again whereas, I think administering saline or something of that type would potentially lead to quite a significant absorption of fluid.

Diana - Water on its own probably wouldn’t do very much, but a saline solution could give one a better chance of a drink. But what if you're stuck for saline drips and all you've got is a much saltier seawater?

That's from the same link as I provided to you earlier, but you've only quoted the first paragraph which relates to a saline (not very salty) concentration. In the second paragraph they address seawater.

[EternalOptimist]

That's from the same link as I provided to you earlier, but you've only quoted the first paragraph which relates to a saline (not very salty) concentration. In the second paragraph they address seawater.

no the rest of it was about putting things up your bum at cocktail parties or something

[TimberWolf]

no the rest of it was about putting things up your bum at cocktail parties or something

You didn't cite your reference. You can see the rest here and it relates to seawater.

Ari - Unfortunately, giving yourself a seawater enema for hydration if you've had the misfortune to be stranded at sea is a complete thermodynamic nonstarter. The problem is that the salt in seawater is much more concentrated than the concentration of all the various solutes found in body tissues. Since, to a first approximation at least, the gut can be thought of as a sort of semipermeable membrane, this will lead to water molecules tending to move from the body through the gut wall, and into the seawater to reduce the concentration difference. This process where water moves along its own concentration gradient across a semipermeable membrane is called osmosis, and it’s very important in biology. In this case it will actually result in you becoming increasingly dehydrated. The situation is reversed with freshwater which would be successfully absorbed. Having said that, neither procedure would be very safe especially if the water was dirty. So, giving yourself a seawater enema if you're trapped at sea is likely to make you lose water. Of course, giving yourself a seawater enema if you're trapped at a cocktail party is likely to make you lose friends as well.

The part you quoted relates to brackish water and saline, and even there he says ions are absorbed in the large intestine, to increase the osmotic potential in order to absorb fluids (liquids and solids presumably being still watery, i.e. less salty than blood). That is, it suggests the salt in seawater would be absorbed. He also says saline, being of blood concentration might be absorbed in large quantities in the large intestine. But the second paragraph that you didn't quote addresses the issue without any suppositions about seawater needing to be made.

[AtW]

Oh FFS, enough already!

Move thsi thread to light relief where it belongs!!!

[TimberWolf]

Oh FFS, enough already!

Move thsi thread to light relief where it belongs!!!

Excuse me, but we are talking piss.