In the late 1890s, as the germ theory gained prominence, a new invention came on the scene: the stainless-steel roller press. This gleaming contraption allowed manufacturers to extract oil from hard seeds like corn kernels, cottonseeds, and soybeans. Primitive stone presses worked only for oily seeds like sesame, flax, and rapeseed and for oily fruits like olives, coconuts, and palm fruit. A traditional stone press extracts the oil slowly and without heat, so the final product is natural and tends to be healthy.

Oil from cottonseed—a waste product of the cotton industry—was the first fabrication of the new mechanized press. Like all industrial seed oils, cottonseed oil oozes out of the crushed seed as a dark, smelly gunk, something no one in his right mind would consume. High-temperature processing, which involves alkaline chemicals, deodorizing, bleaching, and hydrogenation (a process that turns a liquid oil into a solid) transforms the dark gunk into a product suitable for its initial use: candles. 

Proctor & Gamble, located in Cincinnati, perfected the refining process for this industrial product. But with electrification, the candle industry declined. What were they going to do with the expensive processing infrastructure in which they had invested? Feed the oil to people, of course.

The result was a profound change in the food supply, something the world had never seen. It took about forty years for industrial seed oils—as both hard, partially hydrogenated fats and as liquid cooking oils—to replace animal fats for cooking and baking; cheap industrial oils from cottonseed, corn, and soybeans made the processed-food industry possible—so cheap and so profitable that the industry had plenty of money for marketing campaigns and plenty of clout to influence university research and government policy. 

For years, health organizations including the World Health Organization (WHO) have recommended a diet containing industrially processed vegetable oils instead of natural animal fats.

No dietary change has ever been as deleterious to health as the advent of industrial seed oils, usually called “vegetable oils”; loaded with chemicals, intrinsically rancid, and lacking the many essential nutrients that humankind gets exclusively from animal fats like butter, lard, poultry fat, and tallow, they are a recipe for poor health. Chronic disease such as heart disease and cancer, kidney problems, Alzheimer’s, and immune disorders have increased in lockstep with the increase in vegetable oil consumption. Moreover, the type of fat molecules in vegetable oil (omega-6 linoleic acid) can make our bodies more sensitive to the effects of electromagnetic radiation.