The vet cleared up our understanding of this last week as well. It is not a matter of adding grain to the diet but rather if grain is missing from the dog food, it is typically replaced w legumes and peas, which prohibits the absorption of taurine, which then leads to heart problems in dogs. However, even the research is not conclusive yet.
We already bought two huge bags of grain free dog food…so probably will just switch things up in between with a grain inclusive dog food.