water in body

noagname

ok,
this is a couple of questions in one
where is water stored in your body?
i know some is stored in your blood stream, but then does it ever get emptied out
and if it does then why are some athletes not allowed to drink a lot of water
i heard that they will get to much water in there blood
how do you sweat and while you are sick does it help to sweat?

Invictious

Cells, every single cell contains water. Without water in cells...well, you can guess what happens.

Athletes should not drink large volumes of water during intense exercise or right after exercise mainly for one reason:
You are sweating profusely and you are losing salts. By having a large intake of water, it dilutes your blood even further and you get hyponatremia. Then you get water poisoning
then you die.

DaleSpam

Hence gatorade.

CaptainQuasar

The salt and potassium and other things dissolved in the water in your body actually give that water an electrical charge. Some of the dissolved substances give it a positive charge and some give it a negative charge and the positive and negative charges must be kept in balance. This is what's called electrolyte balance.

If you drink too much pure water (not just while you're exercising - any time), which is more electrically neutral, it causes the charged water and substances to move around inside your body in a way that completely screws up the function of many of your bodily systems. It can actually kill you. This is called overhydration, water intoxication, or water poisoning.

noagname

ok i never thought you could die like.

CaptainQuasar

Yeah, a fair number of people die because they don't realize this.

Defennder

Just how much water is too much?

CaptainQuasar

My expectation would be that it would be different based upon body mass, but I'm not sure. This one in Canada involved a woman drinking more than 40oz. but they didn't know the exact amount.

Moonbear

We've had some threads in the past on water intoxication. You might want to search in the biology forum for them...they would have predated the existence of the medical sciences forum. I know I've dug up some clinical studies on it and posted in those threads, so you might want to take a look at them to understand it better if you're curious about it.

noagname

well my only other question is would something like Gatorade hurt you

CaptainQuasar

I don't know the answer to the Gatorade question. But even if someone here knew how much Gatorade you would have to drink to hurt you, they probably wouldn't put it in writing because it would make it look like PF was libeling Gatorade.

My suggestion would be to follow Moonbear's advice and track down older water intoxication threads. It's probably safe to say that you should not drink an amount of Gatorade equivalent to the amount of water that would kill you.

Andy Resnick

Your kidneys control the overall amount of water and salt in your body (homeostasis). Typically, our bodily fluids are at around 320 mOsm, but there is a huge difference between the solution inside a cell (120 mOsm potassium, 5 mOsm sodium) and outside a cell (120 mOsm sodium, 5 mOsm potassium). This difference is used by every cell to "do" things: muscle contraction, nerve impulses, etc. etc. There's another ~50 mOsm of cloride, ~30 mOsm of bicarbonate, ~5 mOsm of calcium (extracellular), and so on.

Sweat is mostly Na, Cl and water. During normal perspiration, the salt is re-absorbed by the epithelial layer, with the overall result of slow loss of water- drinking plain water is sufficient to maintain homeostasis. During extreme perspiration, there is both loss of salt and water, requiring replacement of salt as well. That is, simply drinking salty water is best for heatstroke and the like.

Gatorade and the like do more than simply replace salt and water. "sports drinks" are a combination of salt, water, and glucose. The glucose is there (in theory) to replenish depleted energy stores within muscles which occurs during excersise. The gut and renal epithelia couples glucose and salt uptake for a couple of reasons. Drinking salty sugar water will allow faster absorption of the sugar than drinking plain sugar water.

It's possible to overdose on distilled water (never drink deionized water!) by washing out the osmotic gradient present in the kidney, required for urine concentration (countercurrent hypothesis). It's possible to overdose on anything! Drinking sufficient quantities of gatorade, fast enough, will also result in damage- I'm not sure what the mechanism is, but all that stuff has to go somewhere.

Sweating is part of the excretion mechanism and relates to maintainance of core body temperature. I don't think "sweating out a cold" works because of any immunological benefit- what is excreted is salty water, not bacteria or viruses. Cystic Fibrosis patients have a higher osmotic concentration in their sweat than normal.

CaptainQuasar

Wow Andy, thanks for all the detail. I was hoping someone would come along with this much knowledge.

Why is it bad to drink deionized water? Not that I plan to. Is that something you can even get in stores? Does it bond to something inside your body?

noagname

I think i should also say thanks. You answered all of my questions and i really like the sweat part of it. Now i can show my parents that.

Andy Resnick

It's a question of osmolarity. Water comes in a lot of 'flavors' here- deionized, double-distilled, endotoxin-free, autoclaved, and in combination with each other. Mostly they are the same thing, only the method of preparation is different. DI water has been run through a revere-osmosis device, while dd water has been run through a 'still'. The mice here are fed on dd-autoclaved water. I think the endotoxin-free stuff is used for DNA preps...

Drinking straight hypo-osmotic water puts a lot of stress on the kidneys, and can lead to lysing the epithelial tissue. I'm not sure what the 'safe dose' is....

I just got our osmometer up and running again, I'm curious what the osmolarity of tap water, bottled water, etc. is... but I'm sure they have a higher osmolarity than DI or dd water.

The other thing is that DI/dd water is highly corrosive to metals, as well as slightly acidic.

CaptainQuasar

Thanks for the warning. Do you think that the jugs that are specifically labeled “distilled water” as opposed to “spring water” (I'm in the U.S.) might have a high enough osmolarity to avoid?

Andy Resnick

I just ran some samples of dd and tap water on our vapor pressure osmometer: there is no substantial difference between the two- tap water came out as 28 mOsm, dd came out as 24 mOsm. It's not clear if 3 mOsm is statistically significant.

So- there should no biological difference between drinking dd, DI, or tap water based on the osmolarity. Tap water has trace elements that are removed by distillation, so there may be an issue if one only drinks and uses distilled water.

Urban myth debunked!