Seed oils have high amounts of polyunsaturated omega-6 fatty acids (PUFAs), notably linoleic acid.
An evolutionarily appropriate ratio of omega-6 to omega-3 would have been around 1:1.
Today it's up to 20:1. (r)
This unnatural amount of PUFA causes problems.
Obesity
PUFAs can sensitize fat cells to insulin, causing them to store more fat than they otherwise
would/could.
Further, seed oils increase the production of endocannabinoids, specifically 2-AG and anandamide, giving you the "munchies."
These are compounds that mess with satiety receptors in your brain and make you want to eat. (r)
Combined, these two mechanisms create a vicious cycle of hunger and excess fat storage capacity.
Disease
PUFAs are defined by their multiple double bonds. These make them highly unstable. They are so unstable we have to add harmful chemicals (BHA, BHT, TBHQ), to try and prevent rancidity. Of course, some of these additives have been shown to be carcinogenic. (r)
Regardless, these PUFAs still breakdown.
Under heat they release toxic aldehydes in high concentrations, in certain instances, 100-200X the WHO daily safety limit. (r)
However, even if you don't heat them they are still problematic.
For example,
if you cover your salad in vegetable oil, you consume a lot of linoleic acid which will breakdown into OXLAMS (oxidative by-products of linoleic acid metabolism), like 4-Hydroxynonenal (4-HNE) and 13-Hydroxyoctadecadienoic acid (13-HODE) in the body.
These toxic byproducts ruin mitochondria. (r)
The resulting metabolic dysfunction is a hallmark of disease and linked with cancer, heart disease, autoimmune conditions, and brain impairments in humans. (r, r, r, r, r)
It takes years to remove these toxic fats. (r)
While the CDC is recommending we cut saturated fat, we should be cutting the polyunsaturated fats.
