I wouldn't say vertebrates cause issues to all frogs general as a fact. I remember reading about the stomach content of ornate pacman frogs in the wild. They had other frogs as their top gut content. Pacman frogs are known to be frog eaters, thus their shape. However they do not live long healthy lives in the wild either. So its possible that a frog diet leads getting them to a breeding/large size the quickest, but might be a risky food item. The disease risk would be very great imo.

It would be very interesting to see what African Bullfrogs have in their stomachs in the wild. It would be my guess that the large male would have a lot large prey items but also a very diverse diet. I wish there was more research and facts that were backed up by documented research. Sublime might I ask where you got your enzyme information from? I am not disagreeing or debating what you said in any way, I would like to read it.

I wish to have my frog live long and healthy. For me it seems like nightcrawlers and the occasional large item are working, so I will continue that route.

It is pretty obvious even if its not proven, that an only rodent fed frog has health problems. Dieng early, lethargic, blind ...ect