In general foods that are legally edible for humans will be made with higher-quality ingredients and have a lower risk of contamination than will those made specifically for our animal companions. More specifically, human grade products are not waste products. Animal grade products often are.
When you see protein as an animal grade ingredient, it’s not the kind of meat we might sit down to dinner with. Roadkill, euthanized animals, etc. are not infrequently included in these products. There have been studies which have found dog DNA in dog food. And grains, which our cats and dogs don’t need at all may be the waste products of alcohol production, etc.! In general, our animal’s food is often made of leftover garbage, is highly inflammatory and severely lacking in nutrition.
Human grade foods are more costly. That said, you can make a big difference in your animal’s health by just tossing in some fresh fruits and vegetables, an occasional leftover piece of steak, chicken, fish, etc.