I have always fed a grain-free diet, with no artificial colors, no wheat, corn, soy, etc. and it has never made a difference for me. I used to feed Natural Balance Sweet Potato & Venison, but felt it was too low quality, so I switched to Orijen 6 Fresh Fish about 6 months ago. They do wonderful on it, but tear stains never went away from either food. Unless your dog is allergic to something in a specific food, it won't "cause" tear staining (unless it's got a bunch of artificial colors, etc perhaps).