Grain free dog food is okay for dogs to eat in moderation but grain free dog food is not any better than regular dog food.
Actually grain free dog food may actually be bad or worse for your dog to eat than regular dog food.
That is because your dog needs some grains in it's diet to help keep a healthy heart.
Dogs who eat strictly grain free dog food seem to have more heart issues and heart disease and some die earlier than those who eat regular dog food.
Dogs do need grain in their diet to stay healthy.
If the dog is obese then feeding them some grain free dog food may be better for them but I would recommend feeding the dog mostly grain based dog food.