Many vets recommend that a cat with kidney issues have a low protein diet. What they're really getting at is that phosphorus has been linked to kidney issues and high protein typically means high phosphorus. However, the vets on the cutting edge are now recommending that a cat with early stage kidney disease continue on a high protein, grain free canned diet and as the disease progresses then add phosphorus binders.
Many people mistakenly believe that grain free equates to high protein. While many grain free foods are high protein, not all of them are. Conversely, I'm not aware of any high protein food that contain grains.
A high protein/phosphorus diet will not cause kidney disease, so there is no reason to avoid a high protein grain free diet with a known healthy cat. (By known healthy I mean one that has recent bloodwork within the last year if over age 10ish).
Holly, Misty & their friend, Jake, the dog.
Onyx, Callie May, Maggie & Kobi forever in my heart.
Yes, I know I need a new signature pic...someday...