Four years ago, I detoxed and went to pure foods that aren't overprocessed. I didn't give up gluten, but limit it to a bowl of whole-wheat cereal and a slice of whole grain bread or some other pure grain. Without any added gluten, whey, cornsyrup, no artificial anything...and sticking to whole grain, two servings is fine.
I agree it's the processing. But I'd say it's also the additives.
Yep. Processing and additives go pretty much hand in hand. White flour is a good example. Process the flour down until all the is left is white starch and then "enrich" to add back the vitamins the processing removed. Sodium is one additive that gets me. Why do a can of green beans need an entire days worth of sodium added?