Health Myth: Fat

In So Butter is Good For You (Briebart.com, 2-11-15; give credit to Nina Teicholz for much/most of the research on this issue!!), James Delingpole writes:

The big story in all the papers this week is that butter is good for you, after all.

I say “after all” because for most of my life butter has been widely touted by the Health Establishment as the dietary equivalent of Polonium-210. 
…
Let me offer a brief summary of the salient points.

1. Scientist hypothesises novel scare-theory which, if true, will require radical action to prevent the Bad Thing happening.

2. Government seizes on this theory because “Why not?
…
4. Dissenting scientists are mocked and marginalised.

5. …Health problems, far from being resolved, seem to increase….

6. Many years later, the ugly truth begins to emerge. … And, of course, no heads roll for the decades’ worth of damage inflicted by government regulation and false advice on a population which foolishly trusted the government because government’s don’t pass laws without first doing their due dilligence do they?

Eat fat: butter, egg yolks, fatty meat. Your brain and body will love you for it. (So your grades will be better.) And your heart, which needs fats to work. Unlike other muscles in your body, the heart does not use sugars for energy. 

Again: we see the need to think independently and inductively here. We see the need to be trained in things most of our modern school system fails at.

What other myths, errors, and lies do you know of? With some thought and investigation, what else can you learn is right or wrong? A good place to start is to consider what primitive cultures ate.