Surprisingly, vets don't have to take many classes on nutrition to be a vet. The majority of the time, the few nutrition classes vet schools have are run by Hill's Science Diet and Royal Canin themselves. These brands are crazy overpriced for the overall low quality nutrition the food provides. While it is true that certain grain free diets can cause heart problems, I've seen studies in Europe linking it to an Immunol disorder, which may be from vaccines. By all means obviously vaccinate your pets still, but the link to the problem isn't clear yet. Dogs typically can't digest grain well or at all.My vet told me it’s not a grain free diet that’s bad it’s grain free dog food specifically. It’s been linked to canine heart disease and no one knows why so it’s best to just avoid it all together.