[KempyKolibri]

Problem in the 70s was trans fats. Now they're no longer a risk, replacing butter with margarine is a solid evidence-based decision for one's health (though not so much for one's enjoyment!).

[literalAardvark]

Hang on, there's such a thing as non-trans margarine? Sheesh, I'm behind the times.

(And really, margarine can be plenty tasty. As a kid I actually preferred it to butter for some reason.)

[KempyKolibri]

Literally all of them now (in the US and UK at least). Trans fats in industrially produced foods are banned.

[literalAardvark]

Not entirely, pastry still has lots of trans fats, but they're probably essential.