"There is no single ideal food for all cats."

They're obligate carnivores. In the wild, the relatives of domestic cats would largely eat very little non-animal matter, if at all. Their bodies are not designed for eating plant matter (this kibble is made of cereal?). Their guts for one are too short. On the rare occasion a cat opts to eat grass, it's often because the cat isn't feeling well and needs to eat something that will induce vomiting.

Wikipedia's take on cats - here

When I had a cat, they lived on fish and tinned meat. In the early days, we'd give them the occasional 'cat love' tablet. God knows what it had in it but they would go nuts if you offered them one. Back in the 1980s. Hope that helps.