I drink tea frequently, at least two to three cups a day. Usually black tea, but occasionally green.
Some googling reveals that some (unknown) black tea has a Ph value of 4.9, indicating acidity. I know acids are bad for teeth. So, how bad is tea for your teeth versus a control beverage of water, for example?
A simple Google search reveals several pages of speculative answers from morons as well as self-promotion from sellers of teeth whitening products. Hence I turn to the far more erudite teeming masses. (I tried a search here as well, but “tea” is too short to search for.)