LoveCats - I did have a bit of a headache for the first three days but they were not too bad. Tylenol helped. I only drank one to two diet cokes a day, but there was nothing like that first sip. I did try one last week when I was eating out and it tasted like chemicals to me. So I tossed it and got an ice tea instead. I am drinking lots of water and some unsweetened ice tea. I have tried La Croix but I don't love it and since carbonation is still bad for your bone density I think I will just stick to tea and water. I do use fresh limes (they are really cheap down here) sometimes in my water.