Cats are obligate (strict) carnivores. Humans (and dogs) are omnivores. We benefit from the nutrients found in meats, fruits, vegetables, dairy products, and grains, while cats only need little dead animals — high in protein, fat, and moisture. A little bit of grain in the stomach of a mouse might provide additional fiber or micronutrients. But the majority of cat kibble, and almost every other cat food you'll find in your supermarket, is loaded with cheap grain and vegetables, like corn and potatoes, instead of the animal protein and fat that cats need.
Rather than rehash all the arguments against dry food and in support of canned food — and against canned food and in favor of a raw diet, I welcome you to visit the sources that educated me. If you're curious and open-minded, as I was, I think you'll be powerfully persuaded:
Feeding Your Cat: The Basics of Feline Nutrition by Lisa Pierson, DVM
10 Reasons Why Dry Food is Bad for Cats and Dogs by Dr. Jean Hovfe
Canned Cat Food: Can Your Cat Afford to Live Without It? by Franny Syufy
Cats, Carbs, and Calories: An Obligate Carnivore's Perspective, by Tracy Dion
Deconstructing the Regulatory Facade: Why Confused Consumers Feed their Pets Ring Dings and Krispy Kremes by Justine S. Patrick (read this law student's exposé with caution: if you feed your cat grocery-story kibble, you won't believe what you may have been feeding your pet)
Complete your crash course in feline nutrition by browsing the topics on this excellent site: The Feline Nutrition Education Society.
If you work your way through a decent amount of this, you deserve a round of applause and a Scout Badge. You've just spent more time learning about how to feed your cat than your veterinarian probably spent throughout his or her training. I hope that's changed, but I keep reading that, not so long ago, vets received only one lecture about feline nutrition, presented by those wonderful folks at Hill's. That's why you see all that grain-based kibble for sale at your vet clinic.
I'm going to assume that we are all on the same page now, that we're in agreement with the idea that a raw diet is both the healthiest and the safest diet, while an all-canned diet is still far superior to kibble, at least. (If you're not there yet, go back and read some more, the evidence is pouring in and it's not all anecdotal, although even the anecdotal evidence is becoming overwhelming.)
Ideally, we'd all be standing around grinding up whole chickens, ducks, and lambs and mixing in supplements, or defrosting frozen mice so our cats could bat them around before they bit off their heads. In reality, it's a big, scary leap between pouring kibble to feeding raw. Fortunately, there's a middle ground: commercial frozen or dehydrated raw, sticking with canned food, or both.
So, what raw or canned foods should we buy?
Darned if I know, and I've been trying to figure that out for weeks. More coming soon.
Toffee and Harris contemplate the confusing world of commercial cat food.
And wish they had some of it. In a bowl. Now.