[neilep (OP)]

Thanks to Pauls sick thread (http://www.thenakedscientists.com/forum/index.php?topic=6915.new#new) he has reminded me of a question I've been meaning to ask for ages:

Why does drinking lots of salty water make you nauseated and even sick (vomit)?

[neilep (OP)]

It's funny that I asked this question yesterday because tonight I watched Casino Royale and in it is a scene where Bond is poisoned via a spiked drink  and he drinks a cup of salty water and immediately throws up...........which is nice !

[DoctorBeaver]

It's not so bad if you take out all the fish 1st!  []

[neilep (OP)]

Has this really got you all stumped ?

[lyner]

Blood tastes fairly salty.
Blood will make you sick if you swallow a lot.
Perhaps it's just not a good thing for you to swallow a lot of blood so we have developed a reaction to it.
Under natural (evolutionary) circumstances, there was a much greater chance of getting blood in your stomach than getting salt water (unless you believe the message in The Ascent of Woman).

[Seany]

Maybe it is a natural thing. Our body is not comfortable with too much salt - excess amount of it. Yes, we definitely need quite a large amount of salt in our body, or we will die. So.. If we drink salt water, maybe we have an immediate response from the body to not take it in.. Although that makes it contradictory, seeing that we do need quite a lot of salt.. *Confused*

[neilep (OP)]

The reaction is virtually immediate and I am sure as soon as a highly concentrated salt solution hits the stomach, then the stomach must just violently react !..I just don't know why but do appreciate your kind comments sophiecentaur and seany !

Hmm..I wonder if the larynx and esophagus are causal too !

[chris]

Strong salt solutions are emetogenic (provoke vomiting) because they chemically irritate the GI tract, which is programmed to respond to any irritation by vomiting. Part of the irritation is also gastric and small bowel distention caused by the strong salt solution pulling water out of the tissue to dilute the salt. This uncomfortable stretching triggers reflex vomiting.

It's a protective mechanism. If you were to absorb a heavy salt load it could cause serious problems with the body's salt and water balance, including severe dehydration as the body subsequently excreted the salt in urine.

This is because you would be forced to lose large amounts of water in order to shed the salt (effectively, when the kidney excretes salt ions water follows passively by osmosis, so you have no option but to lose water in order to lose salt).

The body therefore rejects the heavy salt load as vomit because this, in the long run, causes less dehydration than if the salt were to be absorbed.

Blood was also mentioned above and it was speculated that blood is emetogenic because it too contains salt. Whilst it's true that blood is salty (it contains about 130 mMol/l of sodium), that's probably not why it makes you feel sick. It's more likely that the other chemicals it contains, such as serotonin from platelets, are stimulating vomiting. Serotonin is a powerful chemical trigger of vomiting.

Chris