Oh, very bad for you!!! This coming from a former dietcoke-a-holic. The stuff that makes it up is toxic and if it goes bad, can do damage to your insides. I know a woman (who knows someone...yada yada) who had a bad can of soda and was rushed to the hospital. I'd never heard of 'bad' soda but apparently it can happen with this stuff. I don't have my copy of my book handy right now, but I do remember reading that Dr. Atkins discouraged its use, not recommended it.