There is no perfect food. If by chance there were one that everyone agreed was perfect there probably wouldn't be a kitty that would eat it. Add in to it each kitty having their own food sensitivities, possibly health issues, along with their own taste in food it's just a trial and error thing.
You can find articles pro and con for many ingredients. I know Montmorillonite healing clay is used in alternative medicine and there is evidence of people using it going back into ancient times. It is thought to absorb toxins in the intestines. http://spiritdetox.com/the-facts/benefits-of-healing-clay/ I am sure you can find articles that will say it has no place in our pet's food.
You can find articles pro and con for many ingredients. I know Montmorillonite healing clay is used in alternative medicine and there is evidence of people using it going back into ancient times. It is thought to absorb toxins in the intestines. http://spiritdetox.com/the-facts/benefits-of-healing-clay/ I am sure you can find articles that will say it has no place in our pet's food.