the other point i want to make is those people in trials were asked to take 1 spoon of seed oil ... but their diet ALREADY contains several spoons of seed oil at baseline !  

if you have "control" on 5 spoons of seed oil and test group at 6 spoons ( which is more or less what they had ) you can dial in the slightest changes in the study elsewhere to compensate and over-compensate any minor effects this extra spoon would have ...

a proper study would ask what will happen if all plant oils are eliminated from the diet versus control group that eats their normal junk diet.  of course you can't just get people to stop eating junk and you would need to run the study for at least 6 months because that's how long it takes to flush out the fatty acids out of the adipose tissue where they are long-term stored... 

 i used to follow ( and even once went to gym with ) a dude with PHD in biochemistry or something called Chris Masterjohn who had a podcast where he tore these studies apart.  there are some egregious things that take place in those studies - like having one group in a smoking building and another in a non-smoking building and then pretending like this has no effect of heart health and just focusing on difference in diet etc. 

 the point is design of a study is more important than results.

a study can always be designed to produce desired results.