We all know that when we eat a lot of salt it makes us thirsty, and we retain fluid. What happens, physiologically, if rather than giving in to the thirst, we don’t drink anything? Do we become dehydrated?
Not the answer to your question, but here is a Cecil Column..
The answer seems obvious to me, that we will become dehydrated, as there is no intake of water.
Here is another cite I found.
Our brain is 85% water, and if it becomes dehydrated, death is not far behind. Because of this, the brain controls water in the body and will take the water it needs from other parts of the body. This survival mechanism keeps us alive, but at a cost to our bodies other systems.*
When your body gets too hot, it sweats, releasing water which cools your body. When you do not drink enough water your body loses its ability to cool itself off when necessary. Failure to stay hydrated when you are hot can lead to dizziness, fainting, heat shock, and other serious problems.
Before trying to answer your question, it helps to think why eating salty food makes you thirsty in the first place - there are at least two mechanisms at work, each one being more prominent at a different time interval.
Early on after eating salty food (or even while still eating it), you get thirsty because the cells of your mouth and tongue are getting dried out by the salt. In other words, the salt pulls water out of those cells by osmotic action (i.e. water goes from dilute areas to more concentrated ones).
Later on after eating salty food, everything else being equal, your body will need to get rid of all that extra salt. To do so requires water. That is to say, you can’t pee out pure solid salt crystals; the salt must be dissolved in water. The net effect, then, of removing salt from the body is an obligate loss of water from the body as well. As more and more salt is lost, more and more water is lost, and the blood and other fluids in the body become more concentrated. When that happens, it causes you to feel thirsty and thus to take in more water. That will have the effect of diluting back down your blood and other body fluids.
Now, to answer the question, “What happens, physiologically, if rather than giving in to the thirst, we don’t drink anything? Do we become dehydrated?”. Yes, you will get dehydrated. And, obviously, you’ll get thirstier and thirstier. More to the point, if you continue to take in extra salt then, as your body pees it out, more and more water will leave your body with that salt. This loss of water will cause your blood to become more and more concentrated and, if left unchecked, could (eventually) lead to impaired brain function and even a coma or death. As I’m sure you can appreciate, that would take a long time to occur (before which, you’d be so thirsty that you’d drink water from a toilet bowl if there was no other source of water available - thirst is about the most powerful urge we have).
Bearing this in mind . . . are there records of people actually using salt as a means of torture, i.e. feeding salt to a prisoner, with no means of obtaining water?