Most unfortunate. Who the bleep advised you to drink that much acidic juice?
If it was to be attempted, it would have to be on tree ripened, high BRIX lemons. But even then I would not attempt it. That's way too much.
I can't conclude that lemon is a bad substance just because it was abused with bad results. It has its place, but its place is not one quart a day with no high alkaline drinks to balance it.
I have seen similar abuse of pineapple. It dissolved the teeth right off of the guy! He didn't have the sense to stop and was juicing unripened pineapples on a fast. Terrible.
Again, abuse of a food doesn't indicate what the food's worth is if it's used properly. In no way do I like citrus that is picked green and shipped north though. Forget it - I'll do without, thanks.