Oh, I certainly believe that feeding our companion animals foods that are loaded with grains (esp wheat) is damaging for their health.
Once upon a time, in a galaxy far, far away I fed my little darlings.......*gulp*......Purina Beneful.

There, I admitted it. They were in terrible shape, but of course I didn't realize it, I had never seen a dog in really good shape because everyone I knew fed their dogs grocery store food. They were itchy, chubby, had chronic ear infections, poor body composition, low energy, smelly (bodies and breath), had dull and flakey coats, and they were poop machines. They also were reluctant to eat, and would sometimes leave their food in the dish for almost the whole day.
Then I learned about ProPlan. It was supposed to be the "best". So I ran right on down to petco and picked some up. They liked it better than the other stuff and I did notice some improvement. Their coats got a little shinier and less flakey, they lost a little fat and gained more muscle, they had less doggie odor. I thought this stuff was the best.
THEN, about 1 1/2 yrs ago, I learned about the *true* premium kibbles available. I also learned a good deal about canine nutrition, and I was shocked and disgusted at the lengths that some companies will go to in order to create the cheapest food they possibly can while at the same time convincing people that it is the healthiest way to feed their beloved pets (and charging an outrageous amount for it). I also learned that most vets know little or nothing about pet nutrition, and what they do know is taught to them by the Big Three pet food producers (every food you can buy at the grocery store is made by one of only 3 companies).
I have since tried several of the high-end kibbles, and I've found one that I am completely in love with (and so are my babies). My dogs are now shiny, soft, bright-eyed, full of energy, lean, muscular, nice smelling (even their breath), and healthy. They no longer itch or chew their paws, they don't have any more chronic ear problems, they have clean white teeth, they poop a lot less and it doesn't smell nearly so bad.
We have foster dog with us right now, who came to us eating one of the better brands of food (it's better than anything you can get at the grocery store, but it's still loaded with gluten/grains). Since he's been eating the food we serve here, he's shown a huge improvement. Not only is his coat better, but he has filled out with more muscle and is arthritis has improved quite a bit.
Of course, kibble (even the very best kibble) isn't a natural diet for your animal. Doing a carefully researched and planned homecooked or raw diet is the best that you can do. However you need to really know what you are doing in order to properly balance the animal's diet. Personally, I just can't manage feeding 4 dogs a raw or homecooked diet. It's way too much work for me at the present. So they get the best kibble I can get them with add-ins like sardines, mackrel, pumpkin, kefir, cooked veggies, and some meats.
After seeing the changes in my dogs' health, I would never go back to feeding them the way I used to. In fact, I would rather eat gluten myself before I fed them something from the grocery store. These little dogs mean the world to me.
Here are some great websites for anyone who may be interested:
http://mordanna.com/dogfood/http://www.dogaware.com/http://www.gooddogmagazine.com/dogfoodcosts.htm*edited to add one more link