I asked my surgeon at 4 months out and his answer was to try it and if I was OK, then diet soda is OK in moderation. I now find that I can drink it if I let it get a little warm and a little flat. It's very uncomfortble when it is really cold and fizzy. I REALLY dislike the aspartame in Crystal Light and I was sick of plain iced tea and water. I find that I drink about half a can of Coke Zero or Diet A & W a day. I just needed some variety to drink and my surgeon gave it his blessing in moderation, so I see nothing wrong with it.