I'm working through the main link, and commenting as I go. Already this is getting very long. Beware ramble.
I've looked at Linoleic acid and since Linoleic Acid is seen to be a good thing and an essential fatty acid I am not sure about the description of Omega 6 you give implying that it is bad. Happy that too much corn oil is potentially bad.
LA is present in nuts and seeds (and their oils) but is also present in butter and beef. I am assuming that one aim of the trial is to source the LA from vegetable sources instead of from beef and dairy.
All this is a little strange, anyway, because we suspect that LCHF can lower cholesterol and that most cholesterol is manufactured by the body from carbohydrates.
I think the main point of the study is that using corn oil (which happens to be a source of Omega 6) as a major part of the diet may reduce the level of cholesterol in your blood but it doesn't improve your cardiovascular health. In fact, rather the opposite. This is possibly specific to corn oil, not Omega 6 in general.
The control diet was not only heavy in animal fat, but in margarines and shortenings. The latter two items are not necessarily part of an LCHF diet. Shortenings especially can have all sorts of bad stuff, as the term covers any fat that is solid at room temperature, including all sorts of vegetable oils that have been chemically treated. That is, hydrogenated oils. Amazing what you learn.
https://en.wikipedia.org/wiki/Shortening
"Soon after arriving, Kayser made a business deal with Procter & Gamble, and presented the company with two processes to hydrogenate
cottonseed oil, with the intent of creating a raw material for soap.
[2] Since the product looked like
lard, Procter & Gamble instead began selling it as a vegetable fat for cooking purposes in June 1911, calling it "
Crisco", a modification of the phrase "crystallized cottonseed oil"."
So it appears that modern shortening was originally intended to be soap.
Anyway, it looks as though replacing some rather dodgy looking fat sources with Linoleic Acid didn't have the expected improvements in life expectancy. Noting that corn oil was used.
Rather more scarily:
"The intervention group had significant reduction in serum cholesterol compared with controls (mean change from baseline −13.8%
v −1.0%; P<0.001). Kaplan Meier graphs showed no mortality benefit for the intervention group in the full randomized cohort or for any prespecified subgroup. There was a 22% higher risk of death for each 30 mg/dL (0.78 mmol/L) reduction in serum cholesterol in covariate adjusted Cox regression models (hazard ratio 1.22, 95% confidence interval 1.14 to 1.32; P<0.001). "
Which seems to say that lowering the cholesterol level (using their chosen strategy) actually reduced life expectancy. This does seem to tie in with some more modern findings.
Further:
"Our recovery and 2013 publication of previously unpublished data from the Sydney Diet Heart Study (SDHS, 1966-73) belatedly showed that replacement of saturated fat with vegetable oil rich in linoleic acid significantly increased the risks of death from coronary heart disease and all causes, despite lowering serum cholesterol".
Ouch!
If you look up the benefits of corn oil (which seems to come from the people selling it):
https://www.prevention.com/food/food-remedies/corn-oil-lowers-cholesterol-more-olive-oil
"
With countless studies touting its benefits, it's no surprise that olive oil gets all the glory. But now a new study suggests that's not entirely fair: Turns out that corn oil might actually be better at lowering cholesterol than olive oil.
Researchers studied the effects of both oils on 54 healthy men and women. For 21 days, participants were either given four daily tablespoons of corn oil or four tablespoons of olive oil. The results? Corn oil was shown to reduce LDL cholesterol (the bad kind) by almost 11%, while olive oil only lowered it 3.5%. Study participants experienced an 8.2% decrease in total cholesterol with corn oil, compared to just a 1.8% decrease with olive oil.
"
Now further down the article, and:
"The higher risk of death associated with decreased serum cholesterol seems to be driven by the subgroup aged ≥65.
Among participants who were older than 65 at baseline, a 30 mg/dL decrease in serum cholesterol was associated with 35% higher risk of death (hazard ratio 1.35, 95% confidence interval 1.18 to 1.54), whereas among people aged under 65 at baseline there was no relation between the change in serum cholesterol and death (1.01, 0.88 to 1.16)."
Oof! And likewise woot!
If this is true beyond the context of this study then lowering cholesterol seems to make little or no difference unless you are over 65 when it makes a very large difference.
I finally reached the end, where there was a lot of gentle stepping to avoid upsetting people, but there does seem to be no improvement in cardiovascular health
by consuming large amounts of corn oil to force cholesterol levels down.
There also seems to be no evidence that use of significant quantities of Linoleic Acid in general is beneficial.
One thing is that Ancel Keys was very good at predicting the effect of Linoleic Acid on cholesterol levels. Not, perhaps, as good at predicting the benefits.
All in all it is an interesting excursion into the results of not publishing all the information of unique studies and assuming benefits of certain dietary approaches which are not proven.
Largely irrelevant to me from a dietary point of view as I have no intention of taking large amounts of corn oil in my diet. Corn Oil 59% LA, Olive Oil 10% LA so I'll stick with the Extra Virgin, thanks.