Whole lemon is okay, if you feel okay with this. I always suggest things in moderation. Actually I was taking like 2 or 3 large lemons a day for a while and I started to notice the enamel on my teeth eroding (fortunately I have very healthy teeth), no problem though it came back after I stopped for a few weeks. Also sometimes you can feel excess acidity with a whole lemon for a little, while but if you feel okay, then go for it.