That's why you study the boxes before going to purchase, just as honey. The thread is directed towards vomiting, judging by the photo uploaded id doubt its deformity related.
As far as proof.. Well, the only proof I can personally provide is proof that my mantids still live and long after multi tea feeds.
My Childs fed my dog chocolate many times, both dark and regular. The only effect at most was an upset stomach. Completely off topic, but I do not believe that.
Edit: I'm not telling him to do it, I simply implied them as options that I personally have used (except the baby food...) and also friends have used without having an issue.