There are a lot of fillings available for your dog that you can fill in a Kong. Fillings are important for a Kong, as your dog will be spending a lot of time playing and chewing the Kong and ultimately chewing and gulping down what's inside the Kong.  So, as long as you ensure that the filling inside a Kong is healthy and won’t impact the health of your dog, Kong fillings are good for your dogs. Besides, there are a lot of options available as fillers that you can use. There are lots of healthy options that your dog will relish for sure.