I agree that we shouldn't treat humans worse than animals but one important factor here is that humans are much better at expressing themselves when their body badly reacts to some food. Animals often lack the ability to tell you that something is wrong and some may even be genetically inclined to actively hide any issues from you as showing weakness would have gotten their ancestors killed in the wild.

As someone who works very close to this I’m well aware, it’s also very visible when you look at trends over decades in most populations. It has significant impact on a lot of people.