Pet food manufacturers and the veterinarians courted by their sales representatives have convinced most Americans that because commercial pet foods are designed in laboratories by people with academic credentials and because their labels contain long lists of nutrients and claims of being scientifically balanced and nutritionally complete, they are superior to anything an animal might otherwise consumer. Table scraps, raw food, people food and any supplements that might disrupt the commercial food’s precisely controlled distribution of vitamins and minerals are particularly frowned upon.

There is no doubt that commercial pet foods sustain life. Dogs, cats and other animals live for years on foods that come out of bags, can and boxes. But do these foods promote health? If they did, our companion animals would enjoy long, happy lives free of arthritis, hip dysplasia, eye problems, ear problems, fleas and other parasites, gum disease, lick granulomas, thyroid imbalances, skin and coat problems, personality disorders, birth defects, breeding problems, diabetes, cancer and other major and minor illnesses.

Before World War II, most Americans fed their pets raw bones and table scraps. Today, everyone uses convenience foods, and pet food companies are industry giants. Diet isn’t the only thing that has changed. So has life expectancy, with the life span of many breeds now less that half what it was two or three decades ago. Skin and coat problems are so common that we accept them as unavoidable, and today veterinarians routinely treat conditions that used to be unusual or even rare.

Of course, more has changed in the last 50 years than our pet’s diets. Environmental  pollution, toxic chemicals and stress take their toll on companion  animals as much as they do people. But a growing number of experts  attribute the epidemics of modern animal illnesses in large part to  diet.