how is it that a liquid like coffee gives you the urge to pee much faster than water, for example?
There’s a hormone in your body called ADH, or anti-diuretic hormone. As you know, diuresis means “to pee”. So an anti-diuretic hormone causes your body to pee less – specifically by making your pee less watery, but leaving all the bad stuff in there.
Some substances (like caffeine and alcohol) cause your body to produce less ADH. When there is less ADH in your blood, that’s a signal telling your kidneys to leave more water in your pee, causing it to build up faster. This is why you may notice your pee being more clear after drinking these drinks. Your body isn’t producing more urea (the main poison your urine is designed to get rid of), but it’s just getting rid of more water in the process. (edit: see below, the urea isn’t what colors your urine)
This is one reason why staying hydrated is important to prevent hangovers – even small imbalances in your body’s water levels can cause your brain to shrink slightly and cause headaches.
Source: studying to take the MCAT next week.
Side question, why does coffee make you poop? Or is it just me?