It's a known fact that most/all of the research on dog food, is done by dog food companies. Veterinarians while in school, spend very little time studying nutrition. If the only research available is by a dog food company. Then without a doubt, that's what they are given to study.
My thoughts on DMC and grain free.
There has not been a study large enough, or in depth enough. To say grain-free causes DMC, or does not. Do companies have a lot at stake on this study? Absolutely. Some with a lot to gain, and some with a lot to lose.
Just because DMC is showing up in breeds, that it hasn't in the past. Might only mean, more owners are doing extensive testing. I feel the same way about some cancer in dogs.
It's a dog-eat-dog world, and hard to know who to trust.
Not all those who wander are lost.
Life is just a leap of faith.
Spread your arms and hold your breath and always trust your cape.
Two things define you. Your patience when you have nothing, and your attitude when you have everything.