I feed my 1 year old Shih Tzu the Pro Plan Selects CANNED food which does not contain corn, wheat, or by-products. I was previously feeding him super-premium kibble and canned food from brands such as Nature's Variety, Wellness, and Taste of the Wild. After many bouts of diarrhea, vomiting, and constipation I said SCREW IT and put him on the Pro Plan Selects. Lo and behold in a matter of days his stools were normal and he was only having to poop once a day rather than the 2 or 3 times on the others. He also did not have any vomiting. Overall I believe that every dog is different...some will benefit from the premium foods and others won't.