1. Purina Beneful Original Formula
This is one of the worst rated dog foods on the market, and it’s full of harmful fillers. What’s worse, this formula has been cited as the cause of skin and allergy issues, gastrointestinal problems, liver failure, and death in a number of dogs. Even though some dogs don’t experience any ill effects right away, feeding a dog Purina Beneful Original Formula daily is akin to a human eating fast food for each meal — the health benefits are few and far in between and such a diet is generally not worth the risk.