Tea's officially bad for you. I found out through my little office experiment not too long ago. Here's a brief description of it:

First, take some leftover tea from your office mug, look into it and display some slight disgust at the dirtiness.
Next, find a pot of plant, NOT the artificial one, and empty your contents.
Finally, pour some water into a different pot of plant which will serve as the control plant. Notice the changes in a few weeks, where the leaves of the tea-fueled plant will begin dropping off but suprisingly the leaves didn't shrivel up and change colour.
The plant will begin toppling over and the trunk withers away.

I'm sticking to my hot Milo brew. It's simply marvellous!