It's damaging at 'any' time of day!
Pure lemon is for sure, I don't deny that
mark, Caz is right, my son was told by his dentist to avoid citrus fruit as it erodes the enamel on your teeth. If you carry on drinking lemon juice first thing, good idea to have something milky afterwards or rinse your mouth etc.
I agreed with Caz that that it can erode your teeth but felt the amount of dilution I have might prevent it.
Interesting you say milk afterwards is good - so I should simply reverse my routine to be Lemon and then Cereal. Simple fix