I was reading through a page on Ray Peat's website (not a follower but was curious) and he wrote about the damage caused not by Polyunsaturated fats but with unsaturated fats in general. He spoke about limiting all unsaturated fat.
The general understanding I had was that Saturated Fat and Monounsaturated Fat was good while we should limit polyunsaturated fat (also reinforced in the PHD).
Should Monounsaturated Fat be limited too?
This is KGH's posting on fats (from Jun 2009):
Doesn't necessarily give a definitive answer to your question, but he definitely says MUFA is better than PUFA. Three related excerpts:
MUFAs – Monounsaturated fatty acids
A monounsaturated fat (MUFA) has a single carbon- carbon double bond. MUFAs have some unique properties in the diet. Their best known source is olive oil, but they are quite abundant in animal fats.
MUFAs AND OLIVE OIL
Olive oil is a bit of a politically correct fad. It has it's origins of course in the supposed mediterranean diet - of which there are several, and of which only some had any olive oil in them. The support for olive oil was the general scheme (not supported by the evidence) that SFA is bad and MUFA and PUFAs were the alternative.
When you eat animal products and have low carbohydrate intake, you are getting huge amounts of MUFA from the animal fat - check out the MUFA content in a steak or in butter and it nearly matches the sat fat. Bone marrow is the big evolutionary source of MUFAs, not cold pressed olive oil. Of course there is some oxidation going on when you cook with olive oil that will defeat the purpose, so I eat it cold for flavor, but I get plenty of MUFA without olive oil in my animal based diet.
To summarize our PaNu hierarchy of fats and oils:
1) SFA is best because it is not oxidizable.
2) MUFA is next
3) Total PUFA should be as low as possible. N3 PUFA supplements are for people with too much N-6 PUFA from seed oils.
Nutrition reductionism is not a good thing... I don't think I've seen studies supporting the idea that MUFAs are problematic. Most actually point to improved health outcomes and markers with increased MUFA intake.