by Dr. Jody Kaufman
Nutrition theories abound these days. Grain-free diets are better for our pets. Raw diets are the most “natural and what our animals ate in the wild”. Commercial pet foods are all “filler”. It can be difficult to digest all of these theories to come up with a coherent feeding plan. Let’s try to make sense of some of the claims.
Several of the newer “all-natural” diets capitalize on the grain-free craze. However, very few animals are allergic to gluten, the protein molecule in wheat that causes an actual food allergy (usually skin or ear inflammation). Even fewer animals have a gluten hypersensitivity that results in celiac disease, which causes cramping and diarrhea. Moreover, many grains are a good source of carbohydrates, vitamins, and other nutrients. In fact, most cells in the body use carbohydrates as a primary source of energy. The nervous system (brain and nerves) has an absolute requirement for the carbohydrate glucose in order to function. Dietary protein can be used to help maintain muscle and tissue if carbohydrates are available. If not, the protein in the diet gets broken down to make glucose, which is the primary fuel of the body. So it's incorrect to call grains "fillers" when they serve a legitimate role in supplying balanced calories in the diet.
Corn has a particularly bad reputation that is undeserved in many respects. It's actually a good source of carbohydrates, proteins, essential fatty acids, and anti-oxidants such as vitamin E and beta-carotene.And contrary to some claims, corn is not a common cause of allergies. The most common food allergies in dogs are beef, dairy products, and wheat, followed by lamb, egg, chicken, and soy. The most common allergies in cats are beef, dairy products, and fish.
Food allergies arise as a reaction to a specific protein molecule that is absorbed through the gut. Whether it causes dermatological or gastrointestinal issues, the “cure” is to restrict that protein in the diet. Unfortunately, there are no reliable diagnostic blood tests, so the answer is obtained through a strict elimination food trial with a “novel” protein (one that the patient has not encountered). The trial may take as long as 12 weeks, though it may be shorter if the allergic signs improve. These trials are becoming more difficult as many of the “premium” pet foods brands use more exotic sources, so that we have to find ever more uncommon sources for our food trials. Another difficulty is that some manufacturers market diets for allergies, but there may be contamination from other protein sources if their equipment isn’t rigorously cleaned between batches. For these reasons we sometimes prescribe a hydrolyzed diet, one in which the protein is broken down into its constituent amino acids. Thus it provides all the nutrition, but the immune system cannot react to the large protein molecule.
A “filler” is defined as a food ingredient with little or no nutritional value. A by-product is anything that is produced or left over when some other product or ingredient is made. The Association of American Feed Control Officials (AAFCO) guidelines require that by-products come from clean animal parts other than meat, such as liver, kidneys or other organs. Many of the organ meats are abundant in some of the nutrients that may be missing in muscle meats such as calcium and other minerals and vitamins. They cannot include feathers, hooves, hair, hide, or intestinal contents, which WOULD be defined as fillers.
The rationale for raw diet, that it returns our animals to their natural state, misses some essential facts. Thousands of years of selective breeding has changed not just our animals’ appearance, but their physiology. Take a look at a Pekinese or a house cat — we are not feeding wolves or wild felines. A more important reason to avoid raw diets is that they can contain bacterial pathogens such as salmonella that can contaminate kitchen surfaces or utensils, or pass through the feces into the environment. This is especially important for families with children or people who have immune problems. Another issue is that a strictly raw diet may not be truly nutritionally balanced, lacking some essential vitamins and minerals.
There are many other nutritional issues, but hopefully this little appetizer has given you some food for thought.