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Here is the proof that seed oils are harmful to humans… pic.twitter.com/lmApWY6fjY

— Paul Saladino, MD (@paulsaladinomd) September 20, 2024

Where does this idea come about that seed oils and Omega 6s are harmful? 

This is Walter Willett.  He's an MD from Harvard, and I will answer this question.  I think it starts to come from the multiple

Sydney Diet Heart Study, 1966-1973.  

Minnesota Coronary Experiment, 1968-1973 showed that seed oils lead to increased death to people over the age of 65 despite the lowering of LDL.  

Trials like the "Rose Corn Oil Experiment," reviewed in the "Corn Oil in Treatment of Ischemic Heart Disease," 1965, June, showed that replacing saturated fats with corn oil leads to increased rates of cardiovascular disease.

The patients receiving the key treatment (corn oil) fared worse than those in the other two groups: two years from the start of treatment, infarction or death had occurred in one-quarter more of the corn oil than in the control group.

And though there are randomized controlled trials in humans that show that seed oils a negligible effect in human health, these trials almost all have major issues with the way they were conducted that leads to pretty fatal flaws in the study design, and I think that they are not a very valid indicators of whether seed oils are healthy for humans. 

Let's go on and see what Walter Willett has to say next.

I know dozens of studies that show that Omega 6 fatty acids are not pro-inflammatory.  There are a number of the studies that actually say they are anti-inflammatory.

There is very clear evidence that seed oils are pro-inflammatory in humans.  If you look at markers like hetes and hodes which are called oxlams, those are very clearly increased when you eat more seed oils and decreased when you eat less of these.  There are also multiple control trials in humans showing that seed oils increase oxidized LDL, LPa, and LP-PLA2, that's lipoprotein phospholipase A2, that also has been shown to decrease the testosterone in males in the setting of a low-fat diet.  And when the levels of linoleic acid are looked at in the colostrum of mothers who have recently given birth, the more linoleic acid, the more of this Omega-6 fatty acid found in the colostrum of mothers, the worse the outcomes of their children at 2 and 3 years in terms of motor and cognitive outcomes.  There's a lot of evidence that seed oils are harmful that he just seems to be ignoring here.