actually sticks to the colon and may cause blockage. The blockage of the colon may cause an increased risk of cancer of the colon or rectum.Additives and PreservativesAdditives are used in commercial pet foods to improve stability or appearance, and of course provide no nutritional value. These include emulsifiers to prevent water and fat from separating, antioxidants to prevent fat from turning rancid and antimicrobials to reduce spoilage. Added color and flavor make the product more attractive to consumers and their pets.Two-thirds of the pet food manufactured in the United States contains preservatives. In the remaining third, 90% includes ingredients already stabilized by synthetic preservatives. Premixed vitamin additives used to supplement pet food can also contain preservatives. This means that your pet may eat food with several types of preservatives that have been added at the rendering plant, the manufacturing plant and in the supplemental vitamins.In the last 40 years, the number of food additives has greatly increased. Of the more than 8,600 recognized food additives today, no toxicity information is available for 46% of them. Cancer-causing agents are sometimes permitted if they are used at low enough levels. The risk of continued use at these cancer-causing agents has not been studied and the build up of these agents may be harmful. Ethoxyquin (EQ), for example, was found in dogs' livers and tissues months after it had been removed from their diet, and as of July 31, 1997, the FDA's Center for Veterinary Medicine requested that manufacturers reduce the maximum level for EQ be cut in half, to 75 parts per million. Though the law requires studies of direct toxicity of additives and preservatives, most of them have not been tested for their combined effect after ingestion. Three commonly used preservatives, BHA, BHT, and EQ, have a proven synergistic effect that may lead to the development of certain types of cancer. Butylated hydroxyanisole (BHA) and butylated hydroxtoluene (BHT) are the most commonly used antioxidants in processed food for human consumption. For these antioxidants, there is little information documenting their toxicity or the safety of long-term use in pet food.In animal feeds, the most commonly used antioxidant preservative is ethoxyquin. Some pet food critics and veterinarians claim ethoxyquin is a major cause of disease, skin problems, and infertility in dogs. Ethoxyquin is not approved for use as a preservative in human food.Nitrate, also used in meat for human consumption. combines with bacteria, which changes it to another chemical form with carcinogenic properties called nitrosamines. Very small amounts of this chemical can cause acute and chronic liver damage."Natural preservatives" and antioxidants are like Vitamin C, Vitamin E, may seem better than chemical preservatives they may be less effective than chemical preservatives. To make pet food nutritious, manufacturers "fortify" it with vitamins and minerals, which are also just more highly processed, hard to digest chemicals. They have to do this, however, because the other ingredients in the pet food basically have little or no nutrition left after processing. The answer, of course, is to use fresh, whole raw foods that dont need preservatives, that arent