The 5 Worst Ingredients in Pet Food

Use this list to decode pet food labels.

September 5, 2013

You may not realize it, but pet food is made primarily from leftovers from human food production, such as animal products that are unwanted or are condemned for human consumption. The type and quality of pet food ingredients can vary widely, and this is something I cover in detail in Paleo Dog.

While it's true that, in many cases, you get what you pay for—the cheapest pet food is most likely to contain the lowest-quality ingredients—in some cases you may actually be paying a premium price for mediocre foods from makers who spend a bundle on advertising and promotion.


That said, there are a few ingredients to look for on a pet food label that give a good indication of the food's overall quality.

Animal Fat
Animal fat, also called tallow, is a product of rendering. In the rendering process, pieces, parts, and even whole animals are put through a gigantic grinder, then boiled in vats for 30 minutes to several hours. High heat is necessary to kill bacteria, viruses, molds, and other pathogens. The boiling process also allows the fat to separate and float to the top, where it is skimmed off for use in cosmetics, pharmaceuticals, industrial lubricants, and, of course, pet food.

When a pet food company is using fat from a single species, it will say so, but when the ingredient is an inexpensive amalgam of whatever came through the door, the general term "animal fat" must be used. It's not something you want your pet to be eating!

Meat and Bone Meal
Meat and bone meal, or MBM, is another product of rendering. It's a single ingredient, and the term doesn't infer a combination of "meat meal" (which is defined separately) plus bone meal. At the renderer, once the fat is removed from the cooking vat, the remaining material is pressed and dried to yield a fluffy brown powder—that's MBM. It is a high-protein powder commonly used in lower-cost dog and cat foods. MBM is a generic term that can include any one species or a variety.

Both animal fat and MBM may come from any species of animal or from a wide variety of sources, including outdated supermarket meat, livestock that died on the farm, and restaurant waste, such as used grease from deep-fat fryers.

For many years, it's been rumored that euthanized dogs and cats were being processed into pet food, although the pet food industry has always adamantly denied it. The U.S. Food and Drug Administration found no dog or cat DNA in the foods it tested. However, it did conclude that animal fat and meat and bone meal were the ingredients most likely to be associated with the presence of sodium pentobarbital—the drug used by veterinarians and shelters for euthanasia—in the food.

Animal Digest
This ingredient is a flavoring agent commonly sprayed on dry kibbles to make them enticing to dogs and cats. It's made from a stew of animal parts broken down with the use of enzymes or chemicals. Again, the use of the term "animal" means that it may be derived from any one or from many species. This can be a problem if your pet is allergic to a particular animal protein.

Corn Products
Many forms of corn are found in pet foods, including whole grain corn, ground yellow corn (also called corn meal), corn grits, corn bran, corn flour, and corn gluten meal. It's used primarily as a source of "energy," which is simply another word for calories. The vast majority (85 percent) of corn in the U.S. is genetically modified (GMO). Moreover, most poultry and livestock in the U.S. are themselves fed GMO corn, so the chicken, beef, and other meat products in pet food are giving our pets double trouble. Corn gluten meal is especially problematic because it is used primarily as a cheap substitute for meat. Cats and dogs are by nature carnivores and do best with a meat-based diet.

Chemical Preservatives
Many pet foods still contain synthetic preservatives, such as BHA, BHT, propyl gallate, and ethoxyquin. Such chemical preservatives have been linked to a variety of health conditions, including cancer. Opt for foods that use only natural preservatives, such as ascorbic acid (vitamin C), tocopherols (vitamin E), and rosemary oil.

It definitely pays to be a label reader and to choose foods made from good-quality ingredients. It's worth noting that dry foods are more likely to contain rendered ingredients and corn products, and cats in particular are better off with high-moisture foods such as canned, frozen, or homemade. By paying attention to what's in your pet's food, you'll be ensuring your pet a long and healthy life.