A new study appears to have come out supporting the belief that you shouldn’t feed bees foods other than honey. Honey contains chemicals in it which strengthen the bees immune systems. Take that away and bees are more susceptible to disease. Ours bees certainly have been doing fine on a honey only diet. Of course you get less honey but you keep the bees around which is a decent trade-off.
A couple of related links if you want to read more: