Quote:
Originally Posted by pman10
Caffeine is a diuretic (acts in your kidneys to increase sodium uptake), making you pee. It also acts on your anal sphincter muscles, relaxing them so that you can defecate. I don't remember the exact mechanism but probably has something to do with reducing the threshold for contracting those muscles. It also is a GI irritant, which is why your stomach can feel upset with caffeine.
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I think it's the other way around...caffeine is a diuretic that acts to decrease sodium uptake in the kidneys. As sodium is lost, water goes along with it in the nephron of the kidney (to balance osmolarity), making you urinate more frequently.
Alcohol acts by the same exact mechanism, which is why the line to the bathroom in the bar/club is usually out the door and also why the expression "I have to piss like a racehose" is commonly used
Water is pretty important in the body, as you can imagine - that's why your body produces ADH (Anti-diuretic hormone) which works exactly the opposite - it increases water reabsorption in the kidney.
Not sure why caffeine would make you poop more, though.