Naked Science Forum

General Science => General Science => Topic started by: stephencwll on 19/11/2018 17:10:59

Title: Do we pee more than we drink?
Post by: stephencwll on 19/11/2018 17:10:59
I know we get liquid from our food intake, as well as our liquid intake, but does the body produce liquid that we also pee out?

I ask because I'm sure I pee much more than I intake :/
Title: Re: Do we pee more than we drink?
Post by: jimbobghost on 19/11/2018 17:19:48
I am probably the least qualified on this forum to answer technical questions (I am here to learn, not answer questions), but I recall reading something about this.

it seems that the large intestine manages to withdraw water from our waste for recycling. if I recall correctly, without this function, our body would dehydrate very quickly.

(hope my stumbling attempt hasn't stepped on the toes of any scientists herein :) )
Title: Re: Do we pee more than we drink?
Post by: stephencwll on 19/11/2018 17:25:16
I know when my dad had heart failure, his legs swelled up due to fluid build-up. This makes me think there is fluid in our bodies of a sizable proportion. I think they gave him pee tablets to help pee more? I can't recall now.
Title: Re: Do we pee more than we drink?
Post by: jimbobghost on 19/11/2018 17:37:21
again, with apologies to the resident scientists; aren't our bodies about 98 pct water?

added (so as not to take up additional band-width):

the title of the topic used the word "pee", rather than "urinate" or any other slang word...so, when did the word "pee" come into common usage?
Title: Re: Do we pee more than we drink?
Post by: Janus on 19/11/2018 18:06:22
When your body burns food for energy, one of the by-products is water.   So even if you actual fluid intake is low, you can end up with a fair amount of water in your body that you need to get rid off. 
If it wasn't for the fact that we get rid most of this through exhaled moisture in your breath, you'd be be peeing a lot more than you are now.
Title: Re: Do we pee more than we drink?
Post by: davidk on 21/11/2018 12:41:04
The short answer is no.  If one were to pee more than one ingested then the result would be dehydration, a condition that if sustained leads to death.
Water intake normally, on average, is about 2000ml/day from drinking and food.  A further 350-400ml is produced metabolically.
The body has an obligatory solute load (minerals and waste products) of +/- 600mosml to excrete per day.  This is effectively all excreted via the kidneys.  Normal kidneys can concentrate urine to a max of 1200mosml/litre.  So an obligatory urine loss per day is 500ml. [If one were to take in abnormal amounts of solutes eg drinking sea water the obligatory urine loss would be greater than 500ml/d, resulting in more rapid dehydration]
Fluid is also lost per day as insensible loss of 800ml (mostly via the lungs) and 200ml in the faeces i.e. more than metabolic production.  In other words at least 1500ml/d of water is needed to just be in balance. 
Clearly a normal adult has to take in far more water than is lost as urine.
Title: Re: Do we pee more than we drink?
Post by: Petrochemicals on 21/11/2018 19:10:30
But on the whole of it we excrete more h20 than is consumed in chemical form?

And the body is about 70 percent water, as this health care service shows, very reasonable (https://www.buckshealthcare.nhs.uk/About/water_you_made_of.htm) prices too,