Golden Ret Enthusiast
The FDA and UC Davis in July, 2018 published warnings about a correlation between legumes and Cardiomyopathy in Golden Retrievers. It is not the absence of grains per se, it is the use of legumes, especially peas and pea protein, as a starch to hold the kibble together and as a protein source. Those 30/20 working dog kibbles (Sport) are one of the only commercially available brands that do not use any legumes. But they are high in carbohydrates, as is most commercial kibble.
There are plenty of commercially available diets without legumes. Also, the reason for the grain free being singled out so much is that the vast majority of grain free foods have the legumes and not as many foods that are grain inclusive have the legumes. So the recommendation is to pay extra attention to the grain free diets (not all are the issue but a lot) since the dogs coming up with the DCM are dogs on grain free foods.