When it comes to biology & medical issues, including diet, common sense doesn't apply. If it did, you wouldn't have enormous industries dedicated to telling people what to eat. There wouldn't be government bureaus in every country in the world dedicated to this. There's a lot of weird and unintuitive things that common sense wouldn't pick up on.

People these days still don't really understand that orange juice is not healthy. The common sense approach goes "Fruit & vitamin C must be healthy!"