>and as so many diets now incorporate them<

Take a look at ALL of the new pet foods coming out in the US.They  have one thing in common...they are all grain free ;)

>after several millenium of adapting to the diets they have gained from living with humans.<

After hundreds and thousands of years of living without them in their diet.Several millenium is a p*ss in the ocean ;) Evolution doesnt happen in hundreds of years,or maybe even thousands. We will all be dead and buried if or when our canines adapt to an un-natural diet of grains.Personally i dont think it will ever happen.Carnivors very rarely turn into herbivours.Panda's are one of a very few that spring to mind.

If you look at pandas they havn't taken the change well. They live on bamboo but have to continually eat to stay alive this is doing their success no good as they are eating so much bamboo it is running out. Not much of a life. I am sure if they were carnivores they would be much more like other bears and much more active.

Thankfully I don't live in America then or I might find it harder to find the foods to suit my dogs :)  although I expect market forces will continue to dictate a good variety. 
Clearly evolution does occur in milleniums hence the differences we see in the dietary requirements of dogs from areas in the world with very limited diets available. 
My dogs have clearly adapted to a diet containing grains as does every dog I happen to know and myself and all their owners are extant, kicking and not ready to be buried yet ;)

Dr Atkins was ancient, and died following a slip on an icy pavement which caused a head injury! Could have happened to anyone elderly.............

Atkins exposed

Ancient and 18 1/2 stone :)
My father is 75, still visits the gym and has the same waist measurement as the day he got married.  He wouldn't give a carbohydrate free diet the time of day.

Please keep this thread on topic - if you want to start a thread about Atkins or any other human diet plan, please use the Idle Chat board :-)

Soz Jane for taking it off the road a bit....was commenting to the first post with the human/dog weight and starving thingy :D