I don't buy any specific anti-seed-oil claims, but it generally seems like a bad idea to dramatically change where people get a high % of their calories from using a food source that has has in some cases (canola) never before been consumed in humans and in others was consumed only in much smaller quantities. The safest bet is probably to eat diets as closely resembling those of your healthy ancestors as reasonably possible. Human biology is so insanely complex that we're simply never in our lifetimes going to be able to intelligently meddle here.
That we evolved with a food doesn’t mean it’s better for us. There’s an antagonistic pleiotropic effect where our genes make trade offs for our fertile years at the incidental expense of our long term health, and that also incurs trade offs made with so called “ancestral” foods.
I also don’t see how a naturalistic fallacy is more convincing than human health outcome data. If novel foods like canola oil are worse than adapted foods like saturated fats, how come health outcomes improve when you swap saturated fat with canola oil?
In other words, if our best nutrition intervention data doesn’t meet your standard of evidence, then what is the alternative that does? Hand waving over some cozy claims about ancestral foods, evidence be damned?
Specific studies on human health outcomes for different diets show wildly varying things. I’ve seen studies that show terrible effects and studies that show positive effects for canola oil. I also know there’s a huge reproducibility crisis and that I can only critique these studies so far. You say the “best data” shows you’re right, and I’ve seen people with a lot of credentials and other studies that say they’re right that it’s bad.
But what I can do is look at the data we have for overall current human health outcomes, which are absolutely catastrophic considering the advances in medical technology. Clearly we’re eating something we shouldn’t, being exposed to something we shouldn’t, and/or doing things we shouldn’t, on a mass scale, beginning relatively recently.
These seems like as decent a culprit as any. The fact some shmuck in the 1870s London cesspool had a better life expectancy than me is disturbing. We’re clearly doing something massively wrong. I can’t control for pollutants and I get as much activity as I can, and diets the only other thing I can try to control. When we have bad outcomes and multiple changes at once, all I know to do is try to roll back the changes I have control over.
You also have to be careful about how you determine what a "negative" health outcome is. A lot of leaps are taken in the conclusions of papers about various studies.
