IIRC, vegetable oils (unsaturated fats) exploded in popularity in the middle of last century when chemical companies figured out how to mass produce them. Prior to that, we got most of our fats from saturated fats.

Very interesting video about this and more from What I've Learned: https://youtu.be/rQmqVVmMB3k

The Southern Europe have cook with olive oil since centuries. The North and the US, with butter, which is far worse.

Olive oil is not not bad as much as it has good essential aminos, but it still has a lot of palmitic oil. Another not not bad oil commonly sold as a health product is coconut butter, which also has a lot of palmitic oil.

There's a lot of evidence that any fat and any cholesterol is worse than none at all. That means you just have to choose the lesser evil if you want to eat fat, and according to most big population studies that's just eating it raw from plants, like seeds and fruits. The main problem is getting the essential aminos other than ALA, those are found in seaweed or you need to supplement them.

Might want to refresh your understanding here. You've confused oils, amino acids, fatty acids and essential acids of each kind.

The only essential fatty acids are linoleic and alpha-linolenic. It's virtually impossible to be deficient on anything like a normal diet. Oils/fats contain effectively no amino acids, essential or otherwise.

I would call both olive oil and coconut oil moderate sources of palmitic acid. It's present in greater proportion than in most other vegetable oils, but substantially less than in animal fats and palm oil.

Re: seaweed and supplements, you're thinking of DHA, which is non-essential but probably beneficial to consume in amounts greater than can be synthesized. Seaweeds however, containing very little fat overall, are not a very good source.

We'll need to bring back animal fat, butter, lard, et c., then. AFAIK avoiding those (because science said they were bad, at one time) is why we've got all these other fats in our diet to begin with.

No. Avoid butter, fry with olive oil. And threat sugar and/or corn syrup as if they were a plague.

Isn't olive oil terrible for frying? The relatively low smoke point means whatever good properties are in it are likely gone by the time your food is ready.

It's safe enough as it has a smoke point of 193..210°C. But then again deep frying food is not that great for health. I usually add water or sauce to prevent oil from reaching those temperatures and smoking, I believe the term is sautéing. For deep frying I'd rather use refined sunflower oil or rice bran oil since they have a higher smoke point of 232°C, neutral taste, they're low in saturated fats (13..20%) and they're more affordable. You can also use lard or tallow if you can tolerate them, though they're higher in saturated fats (40%). Fried potatoes taste better and have a softer texture when fried in lard. Anyway, don't take my word for it on deep frying, as we almost never deep fry anything.

https://www.oliveoiltimes.com/world/frying-with-olive-oil/30...

The low smoke point makes it perhaps impractical to cook with at high temperature if you don't have good ventilation. But the "good properties" (antioxidants) mean it's probably the best high temperature veg oil, oxidation being the primary issue with veg oil.

Asking honestly: why avoid butter?

Increases LDL cholesterol. I would not totally avoid it, as it's an important source of vitamin A, D and E intake but rather limit butter abuse to about one pack (200..250g) per month per person.

Do you have a link to support that amount? Not disputing, just curious to read through whatever source says that.

No, it's just a self recomandation after eating about three times that amount and doing some blood tests. My LDL was almost twice their guidelines. YMMV. Nutritionists recommed twice to four times that intake (1..2 tbsp or 14..28 g/day).

https://www.healthline.com/nutrition/is-butter-bad-for-you