They do, however, suspect diet plays some role. They're just not sure what it is yet. Taurine deficiencies are known to cause health issues, and certain breeds like American cocker spaniels and golden retrievers are inclined to developing taurine deficiencies, so perhaps it's a nutritional deficit in these alternative kibbles. Some of the dogs were found to have low taurine levels and improved after getting supplements. Still, plenty of others didn't. Maybe it's not taurine, but some other dietary nutrient. The FDA analyzed grain-containing versus grain-free foods and found little difference between them, but that's no guarantee.