I read about book called "the big fat lie" years and years ago. There are some indisputable problems specifically with how canola and flaxseed oils went from being an industrial product that was in excess in the post war economy, to being on everyone's table at every meal. There are meta studies that show benefits from animal fats from healthy naturally fed animals, which of course is not a qualification in the guidance RFK provides. The truth is that separating the most calorically dense part of a whole food and adding it to other foods is never a good idea. Not with tallow, not with canola, not with white rice, or orange juice and really not even with olive oil, just put some olives in there!

Nutritional science has failed us before -- the low fat movement and the panic over salt. And then there's ye olde Food Pyramid which was marketing for Big Ag.

Another one was the concern of soy phytoestrogens, and claiming that only fermented soy was safe.

Much of this had some scientific basis, but science isn't perfect and evolves.

On the other hand, there's ideology and it rejects any scientific reporting that falsifies its beliefs. Science is about being falsifiable -- so when confronted with compelling evidence that earlier understanding is rejected and replaced with new knowledge.

RFK Jr. is an ideologue and is the worst person to be in the role he is. He may get some things right (food dyes, etc), but that's the broken clock effect.