Nutrition Where do all the fluids go?

[steve-in-kville]

Some of the folks here are a lot more well read on these subjects than I am.

I can easy drink two gallons of water a day, depending on my activity levels, outside temps, etc. Somedays I pee like a race horse and the next, hardly at all. I also keep a water bottle on my nightstand to keep things "topped off" overnight so I wake up somewhat hydrated. Do we really expel that much fluid in body sweat and in breathing vapor? Is there a known ratio on our water intake and how its expelled?

Not worried at this point, just more curious than anything. Thanks.

 

[Anna C]

This is a kidney-related subject so is near and dear to my heart! The kidneys regulate your fluid balance, and most of your excess fluid is extracted from the blood by the kidneys and turned into urine. However, you also breathe out quite a bit of water in exhalations, and your skin excretes fluid as sweat. This reference says about a liter or so is sweat and breath, so whatever you drink in addition to that would be urine. On days that you sweat more, you will pee less, if your intake is the same.

Also, I have found that one kidney does all this magical stuff just as well as two.

 

[Steve Freides]

I also keep a water bottle on my nightstand to keep things "topped off" overnight so I wake up somewhat hydrated.

When I was a runner, I did things like this, but no more. Allowing yourself to be thirsty sometimes is in many ways like allowing yourself to be hungry - no harm done, and I think it is beneficial.

-S-

 

[Snowman]

While you could see some difference based on sweating way more or way less day to day, I think @Anna C has pointed out the most likely cause. If you were to weigh yourself every morning and track you *ahem* urinary frequency, you would likely find that you are heavier after a day of not peeing much, and vice versa. The kidneys are affected my number of things, the most obvious being sodium and the second most obvious being insulin. Higher than normal amounts if either will make you retain water.

 

[offwidth]

Even being mildly dehydrated affects performance levels. And thirst is not a good indicator of hydration levels.

 

[steve-in-kville]

So... for the sake of discussion... is urine color still an accurate indicator of hydration?

 

[offwidth]

So... for the sake of discussion... is urine color still an accurate indicator of hydration?

Good question. I don’t know the medical answer one way or the other. But you still see it referenced by doctors and sports professionals.
In a plant I worked once they actually had little posters over the urinals showing various colours and descriptions of each

 

[Anna C]

is urine color still an accurate indicator of hydration?

I asked my brother this question. He is a Nephrologist (a kidney doctor). His answer:

"I've seen a few articles on this. It's pretty clear that urine color (though how defined is vague) is co-related to urine water content. (Not perfectly predictive for each specific sample---correlated in the sense that, for example, living in a certain ZIP Codes correlates with income. But not be true for a specific person in that ZIP code).

A urine that's paler than say, a manila folder, reflects pretty watery urine and that's what I recommend for my kidney stone patients. But for them the goal is water excess so that the kidney dumps it into the urine.

The bigger question of whether "hydration status" is worth monitoring and how is a more contentious one. I don't do sports medicine so can't comment. I will point out that a very pale urine is not just a marker, it may show that the kidney is dumping water (thinks you have too much and is trying to fix it). Similarly, though less reliably as other things can darken urine, a very dark urine indicates your kidney may be trying to conserve water by concentrating it.

These are at the extremes. I don't know what to say about the intermediates.

I'm also not sure how much examination of urine color helps on top of the other system we have built in to monitor water status--being thirsty.

The kidney and the thirst mechanism together have been working together to keep water balance appropriate for the last 300 million years, under the penalty of death. So they do a pretty good job in terms of keeping you safe. I'm not sure they need the brain's help with an extra layer of monitoring .

This is about safety and avoiding illness. I can't comment about sports performance though. "

 

[Anna C]

Allowing yourself to be thirsty sometimes is in many ways like allowing yourself to be hungry - no harm done, and I think it is beneficial.

I also asked my brother this question, too; i.e. is there any harm or benefit to this? He said:

"For most people there is not much risk in getting thirsty. You get thirsty before your blood chemistry is very abnormal, and this escalates rapidly. I worry more about a dedicated athlete who pushes past this warning signal even when severe. I see no advantage to being thirsty though. Unlike food, where being periodically hungry is probably good (since we have no "calorie dumping" mechanism so need to restrict intake), we have a perfectly good water dumping mechanism through the kidney so don't need to restrict. "

 

[Steve Freides]

This was discussed at, if memory serves, Strong Endurance. On a mitochondria level, it's supposed to be good, which is why I recommended it. I should have given that attribution the first time around.

-S-

 

[steve-in-kville]

Thanks for the replies. I was doing some reading over the weekend and came across some material on this. Basically when a person feels bloated, its the kidneys going into a survival mode trying to hang onto water. Anything to that?

 

[Anna C]

Thanks for the replies. I was doing some reading over the weekend and came across some material on this. Basically when a person feels bloated, its the kidneys going into a survival mode trying to hang onto water. Anything to that?

Well it is the kidneys driving the holding onto extra water, but there could be a lot of different reasons for that. Often it's just extra salt onboard and that's the first way that the kidneys deal with that. (That's about the only difference I can tell from having one kidney now -- if I eat a lot of extra salt one day, where I used to retain extra fluid for 6-12 hours, now it's about 24 hours. I can see it in puffy eyes and fingers, and a pound or so on the scale.) Then balance is restored in hours or days as the kidney filters out the extra sodium.

However there are other drivers of extra fluid retention, so a check-in with the doctor would be recommended if any concerns.

 

[steve-in-kville]

Okay, here's another question I've always wondered: if a person leads and unhealthy lifestyle (think heavy drinker, drug user, tons of junk food, etc), from the time they "get clean" how long does it take for the kidneys to filter all the trash out? I've heard everything from a few days to a year or more.

 

[Anna C]

Okay, here's another question I've always wondered: if a person leads and unhealthy lifestyle (think heavy drinker, drug user, tons of junk food, etc), from the time they "get clean" how long does it take for the kidneys to filter all the trash out? I've heard everything from a few days to a year or more.

My guess is just a few days. The liver does a lot of filtering too, and that might take longer. However they both might take longer recovering and getting back to good condition and optimum function, same as the rest of the body.

I'll ask my brother that question and will let you know what he says.

 

[Anna C]

Okay, here's another question I've always wondered: if a person leads and unhealthy lifestyle (think heavy drinker, drug user, tons of junk food, etc), from the time they "get clean" how long does it take for the kidneys to filter all the trash out? I've heard everything from a few days to a year or more.

Alright here's my brother's answer to this question.

"How long does it take the kidney to get rid of toxins if you have a "unhealthy lifestyle?"

First, let's acknowledge that there are a lot of varieties of unhealthy lifestyles which are very different. Unclear how many of them are actually related to toxin accumulation versus misusing your body and subsequent maladaptive changes (either at a cellular or or body level).

Second, be aware that the kidney is in charge of only a certain set of toxins. The ones that dissolve in water, and therefore it can filter out. Things that aren't water soluble (stored in fat) or stashed on proteins the kidney can't deal with – they are the liver's job.

Third, be aware that the kidney is actually in charge of managing things that are much more dangerous than unhealthy lifestyle toxins – your daily diet. If it wasn't all over these, the daily intake of salt, potassium, and water would kill you relatively quickly. This is why dialysis three times a week. We don't consider these toxins just because the kidney can deal with them so well. But they are toxins, and your kidney is built to handle them at high-volume.

So to answer your question: in the kidneys routine work, just dealing with diet, it filters your entire body water multiple times a day. Completely filters it – actually dumped it outside the body, then re-claims everything that it wants to keep again. Like cleaning your room by throwing everything out, then bringing all the furniture back in and leaving the dust outside. A very inefficient system, but guarantees that the default for a new or mystery thing is to throw it away quickly and completely.

The half-life of things managed in this way is about 90-180 minutes. There are a few things that are partially bound proteins and it might drop by about 50% in eight or nine hours. I can't think of any unhealthy toxin unique to an unhealthy lifestyle that the kidney wouldn't washout easily in the course of this routine housekeeping.

I'm not saying that various things you eat can't harm you while they're in you, just that it's not the literal buildup of the toxins in you that's the problem (if the kidney could clear them in the first place). It's their action and effects while they are passing through, not a literal accumulation. It's those effects that last, not the toxins themselves.

Again, this is only in the world of water – soluble toxins handled by the kidney. There are other things that the kidney can't handle and are the liver's job-- things stored in fat can last for days, weeks, or months. But from the kidney side, and as long as your kidneys are working, I really don't think there is any toxic build up.

You might say: really, nothing gets stored away? Well not kidney-handleable things. For example, people who are on high dose of kidney-cleared antibiotics for many months, there's no appreciable longterm buildup of antibiotics (by way of example) once you are in steady state.

I can't speak for the liver, but that's the kidney side."

 

[steve-in-kville]

Thank you (and your brother!) for this response. This is quite insightful. Almost more info than I was looking for but at least now I know!