Why does #1 make me cold and awake, but #2 makes me hot and sleepy?

April 30, 2008 8:51 PM

This question has to do with number 1 and number 2. So if you're not interested in reading about bathroom things skip this question.

Basically, I have noticed the following about myself:

When I have to pee, I feel colder than normal. I also have a hard time falling asleep, and will often wake up if I was sleeping.

When I have to poo, I feel hotter than normal. I also often feel a bit sleepy or lethargic.

I do know that lots of people wake up when they have to pee. Other than that I have no idea whether these are common symptoms or not.

My questions are:

1. Are these common symptoms?
2. Why would my (or any) body react in opposite fashion to these two somewhat related activities?

posted by anonymous to Science & Nature (14 answers total)

I don't know about the temperature thing, but the others seem to match my experience. My wild-ass guess is that the need to pee keeps you awake because there's pressure on your bladder, but urine isn't really involved in metabolism, so it's just uncomfortable. Feces, on the other hand, are byproducts of metabolism; it could be that a full bowel tells the body to slow metabolism, which would make you feel sleepy or lethargic even to the point of overriding the must poo now feeling.

Dear god, why am I posting this in a public forum?
posted by spaceman_spiff at 9:21 PM on April 30, 2008 [2 favorites]

Feeling cooler than normal and needing to pee concurrently could be a product of drinking a lot of (cold) liquid.
posted by Inspector.Gadget at 9:37 PM on April 30, 2008

The #2 thing could have to do with pressure on your sciatic nerve, making you sweat.
posted by clh at 10:18 PM on April 30, 2008

Pure speculation here.

When your bladder is full, and your body knows that it shouldn't let it go - withdrawing warm blood from your extremities (by closing off capillaries in extremities; leaving those areas feeling cold) to around your bladder can help the tissue there relax and expand.

When you have to poop, ... when you feel the need to poop when you normally wouldn't, it could be an acute inflammatory response to some foreign bacterial product, which could account for the other symptoms.
posted by porpoise at 10:33 PM on April 30, 2008

Yes, absolutely.
posted by The Light Fantastic at 11:05 PM on April 30, 2008

When I was river rafting shortly after the spring thaw started, and we were all freezing cold, the guide told us to go pee if we could. She said it with the authority of wisdom passed down among other raft guides. Supposedly, it is because then our bodies have less they need to keep heated. I'm sure someone is going to come and debunk that as an urban myth, but it does verify that others have found that having to pee makes you colder.
posted by salvia at 11:14 PM on April 30, 2008

Um, to clarify, we were not going to make ourselves warmer by peeing in the boat. Rather, we were going to get off the boat, pee in the woods, presumably a sanitary distance from the water, and then get back on the boat.
posted by salvia at 11:15 PM on April 30, 2008 [1 favorite]

Purely anecdotally to back up what salvia said, I always make sure I pee before I go into the walk-in freezer at work. Why? Because I'll be colder in the freezer if I don't. Borne out by my experience. Having a full bladder intensifies feelings of being cold.
posted by seancake at 1:19 AM on May 1, 2008

When caving in New Zealand our guide told us to pee before going in to the cave. The logic being the cold wet water would make us want to go and we would have nowhere to go. We all tried to squeeze one out as it where.

When it's hot you tend to pee less than when you're cold, but this is different to feeling cold when you need to pee.
posted by sdevans at 3:56 AM on May 1, 2008

I remember hearing that your body will always work to make sure your bladder is warm b/c urine is toxic in your bloodstream and if your bladder were to freeze and crack, you could be in serious trouble. Thus, your body will send heat to your bladder, leaving other parts cold. I have no idea if this is true - it does sound sort of kooky. It was told to me by a coworker at an outside job as a reason to always pee if you had to when it was cold - so that your body could stay warm.
posted by lunasol at 5:02 AM on May 1, 2008

From memory, having a full colon has something to do with activating or stimulating the parasympathetic nervous system, which can be calming.

I would have written more but my dog just apparently decided to fire up her parasympathetic nervous system and deposit a mound the size of everest in my living room, causing an evacuation and much gagging. I will post later if someone doesn't beat me to it (leaves to open windows)
posted by tomble at 5:33 AM on May 1, 2008

Whoa, that was NASTY.

Anyway the wikipedia link is pretty detailed.

I remember hearing that your body will always work to make sure your bladder is warm b/c urine is toxic in your bloodstream and if your bladder were to freeze and crack, you could be in serious trouble

Your coworker was wrong - if your body temperature became so low that internal organs actually froze, a little urine escaping would be the very least of your problems.
posted by tomble at 5:40 AM on May 1, 2008

*distant memories of Psch 264 activated*: correlation does not equal causality!

Possibly, the answer is eating: after eating a large meal, you feel both sleepy due to energy being expended on digestion, and the need to shit because, well, you're full of shit. If this is the case, the two are both caused by the same thing, but are not directly related.

Sorry, I hate the word 'poo' for some reason.
posted by crazylegs at 6:06 AM on May 1, 2008

Cecil Adams on piss shiver. To add a little to crazylegs's answer, you feel the need to defecate after a meal because of the gastrocolic reflex.
posted by TedW at 10:13 AM on May 1, 2008