In this presentation, Nina Teicholz reviews the history of seed oils, explaining that fats like soybean, corn, cottonseed, and canola oil are relatively new additions to the human diet. Before the 1900s, most cooking fats in Western countries were traditional animal fats like butter, lard, and tallow. Seed oils first entered the food supply through industrial hydrogenation processes used to create products like Crisco and margarine, which were heavily marketed as modern, “heart-healthy” replacements for animal fats.

These oils became widely accepted not because of strong evidence, but through industry influence and the rise of the diet-heart hypothesis. Organizations like the American Heart Association promoted polyunsaturated vegetable oils beginning in the 1960s, despite clinical trials that failed to show clear reductions in mortality and, in some cases, found higher rates of cancer, gallstones, and stroke in groups consuming more vegetable oils.

A major focus of the talk is the chemical instability of polyunsaturated fats. Because these oils contain multiple double bonds, they oxidize easily when exposed to heat, producing inflammatory and potentially toxic compounds such as aldehydes and acrolein. These oxidation products are absorbed into the body and may contribute to chronic disease processes. Nina concludes that while the evidence is stronger for some outcomes than others, there is substantial reason to question the widespread use of industrial seed oils—especially in fried and ultra-processed foods.