We don't know. We are just learning about this in dogs, and there are many more dogs in the US that are an identifiable breed. Most cats fall into “domestic shorthair”, “domestic longhair”, “Siamese mix”, etc., that are more visual descriptors than breeds. The flag here is notice by veterinary cardiologists that they have begun seeing cardiomyopathies in increasing numbers in breeds not usually known for this. These cases have significant correlation with dogs being on grain-free diets.
The science is just starting, but indicates that the grain-free marketing fad can have serious health consequences.