Most of the commerical pet foods are simply toxic. They are not the equivalent of "junk food" for humans: they are worse. "Junk food" at least has certain minimum safety standards to ensure that they are safe to eat in the short term. There are no such restrictions on pet foods. Quite simply, the companies who make pet food do not care at all about your pets' safety. All they are interested in is making an easy profit. Due to the lack of laws regarding pet food safety, the companies can get away with putting anything they want in. There have been cases where pet food has been found to contain more than the acceptable level of toxic metals such as lead based on the guidelines for children. When you consider that your pet is likely to be much smaller than a human child, the effect on them is going to be much greater. In addition, the meat they use in pet food is normally whatever the meat industry cannot legally give to people. For example, they often use meat from animals who died of disease or who were found dead prior to slaughter. We stopped buying pet food and started cooking for our pets when we realised how terrible the commercial pet foods are.