Reprinted from: http://www.mercola.com
What’s very important for pet owners to know is that “pet food” is a relatively new concept. So, “dog food” and “cat food” you buy from the supermarket has only been around a little over a hundred years.

However, animals have hunted prey or, in the case of dogs, scavenged — for millions of years. And although recent research suggests domesticated carnivores were able to adapt to some degree to starch in the diet as humans became planters and farmers of grains, dogs and cats have most definitely not evolved into vegetarians over time.

Over the last hundred years, major pet food companies have produced most of their products using a base of corn, wheat, rice, or potato. However, our carnivorous pets have not evolved to be able to process those foreign foods.

The good news is dogs and cats are adaptable and resilient unlike other species, for example, snakes. If we suddenly forced snakes to eat grains or consume vegetation, they would simply die, demonstrating rather visibly and quickly that they were not provided the correct food source.

Dogs and cats are among the most resilient animals on the planet. They are able to withstand really significant nutritional abuse, in my opinion, without dying. Degeneration does occur as the result of an inappropriate diet, but sudden death does not.

So one of the reasons we’ve been able to deceive ourselves into believing convenience pet foods are good for dogs and cats is because they don’t die immediately of acute starvation. For a hundred years our pets have been fed inappropriate diets that have kept them alive, but far from thriving like their wild relatives. Instead, we’ve created dozens of generations of nutritionally weakened animals that suffer from degenerative diseases linked to nutritional deficiencies – a link the traditional veterinary community has not acknowledged.

The Pottenger cat study is one example of how our current system of nourishing pets creates chronic disease.

The truth is that our pet population provides a place for recycling waste from the human food industry. Grains that fail inspection, uninspected pieces and parts of waste from the seafood industry, leftover restaurant grease, deceased livestock, and even roadkill is collected and disposed of through rendering — a process that converts all sorts of human food industry waste into raw materials for the pet food industry.

These raw materials are purchased by huge pet food manufacturers – makers of the big name brands your parents and friends have probably used for the last 50 years. These manufacturers blend the rendered fat and meat with a large amount of starch fillers. They add bulk vitamin and mineral supplements, and then they extrude the mix at high temperatures, creating all sorts of toxic reactions including advanced glycation end products and heterocyclic amines. They call this “pet food” and sell it to customers at an unbelievable profit.

Is the entire system flawed? Yes. But pet food industry giants are realizing that pet owners are becoming more educated about their flawed system, and they are trying to clean up their image. We are beginning to see words like “natural” and “no byproducts” on labels. We’re beginning to see “grain-free” and “naturally preserved” on labels as well. Manufacturers are hearing the grumbles of educated pet owners and are changing their marketing to try to regain lost customers.