Speaking of boxed cereals - that stuff is like rat poison - literally! I read of a study done once, in which there were two sets of test rats. One set was fed nothing but boxed cereals. The other group was fed nothing but the BOXES the cereal came in.
All of the cereal-eating rats died first. Yes, the cardboard eating rats outlived the cereal-eating rats!

The heat extrusion process that boxed cereals goes through, turns their ingredients rancid, and makes them toxic - it's like rat poison. Stay away from boxed cereals.