QotW - How quickly does my tea become pee?

Ricky Nathvani put this question to David Wheeler from University College London.

David - When we drink a cup of tea, the components of the tea will be absorbed from the intestines into the body. So, for example, the water from the tea will be absorbed, the proteins and fats from the milk will be absorbed and the sugar, if we added it to the tea, will be absorbed. These different components are then distributed to different parts of the body and the bloodstream.

Ricky - OK. So the tea gets out of our digestive tract through the intestines and into the bloodstream, but how does the tea actually become pee?

David - The fluid is critical, obviously, for normal health and the fluid balance in the body is tightly regulated by the kidneys. So if when Steven drank the cup of tea he didn’t really need the extra fluid, then the kidneys could get rid of that fluid fairly quickly. We could think of this as a bathtub full of water with an overflow. If we add another jug of water to the bath, then some of the water in the bath will go down the overflow pipe. Now this may not be not be the same water that we’ve just added in, but it will be from the same pool of water that we’ve just added the jug to.

Ricky - Aha. So if your blood is like a bathtub with a capacity for carrying a certain amount of water, then adding in too much will cause it to spill over when it’s in the kidneys and make urine. Although it’s difficult to say how much of that came from the new water, or the water that was already there before you drank your tea, some parts of your tea could leave your body within thirty minutes. Thanks for clearing that up for us David. And with all this talk of peeing - I think I have to go.

但之前,偷偷撒尿k at our question for next week when we try to shine the light on this question from Phillip:

Phillip - My home in Cambridge has about 60 percent compact fluorescent light bulbs and the rest are LEDs. Should I be chucking out the former, even though they still work, on the grounds that they use lots of power compared with LEDs or should I just wait until they break over time and only replace them with LEDs then?