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July 10, 2026 · 8 min read

Fat of The Land - Part 10 - The Oil They Have to Deodorize and Refine to Make It Edible

By Raiden DeLuca

Seed oils are the most feared food on the internet right now, demonized by nearly every health influencer with a following. The whole fight is wildly polarized, one camp swearing they are harmless and another swearing they are poison, and the real answer sits in the more nuanced middle that neither side wants to sell you. Most of the fear, as it turns out, is aimed at the wrong part. The claims people shout loudest, that the linoleic acid sets your body on fire and gives you heart disease, are the ones that fall apart fastest under real scrutiny, while the parts that should give you pause barely get mentioned. The place we need to start is how the oil is made, because that part is as bad as you have heard.

What is in the bottle

Let me walk you through how a bottle of canola or soybean oil is really made, because it reads like a chemistry process, and it is one. The seeds are cleaned, heated, and pressed, and then the crushed mash is washed with hexane, a petroleum solvent, to strip out the last of the oil. What comes out is not something you would want to eat. The crude oil is dark, it smells rank, and it tastes acrid, so it runs through the rest of the line to be fixed: degummed, refined with more chemicals, bleached to pull the color out, and deodorized under high heat to drive off the smell and taste of the rancidity it carries by default. Only after all of that does it become the clear, neutral, odorless oil on the shelf.

The process exists to take something inedible and make it edible, to hide what the oil is behind bleaching and deodorizing. Butter is churned cream. Olive oil is pressed olives. Seed oil is an industrial product engineered, step by step, to pass as food. That alone is reason to be wary of it, before a single health study enters the picture.

The number that should bother you

For most of human history, linoleic acid, the main fat in these oils, made up around 2 percent of the calories people ate. Today it is somewhere around 8 to 10 percent, and higher for plenty of people, because seed oils are in nearly everything that comes in a package. That is roughly 3 to 4 times more of a single fatty acid than humans ever ate, arriving in about a century, which is nothing on the timescale of how long people have been eating.

Your body builds that fat into itself. The fatty acids you eat get worked into the membranes of your cells, so a diet running this high in linoleic acid slowly shifts what you are physically made of toward a more fragile, more oxidation-prone version. We are, in a real sense, running an experiment on ourselves that no generation before us ran, and we are the ones being measured.

The real problem is heat

The oil turns most harmful in a hot pan. Polyunsaturated fat is full of double bonds, and double bonds are the weak points oxidation attacks. Pour these oils into a fryer, hold them hot for hours, and reuse them the way a restaurant does, and they break down into a soup of oxidation products, including aldehydes that are toxic in their own right and end up in the food. This is the part of the seed oil case resting on the firmest science, and it is specifically about high heat and repeated frying, not the spoonful in a salad dressing sitting cold in your fridge. The single highest-value move with these oils is to never fry or pan-cook with them.

Where the fear gets oversold

The claim you hear most is that linoleic acid is inflammatory, that eating it sets a fire going inside you. The pathway sounds convincing, since linoleic acid is the parent of arachidonic acid, which feeds inflammatory signaling molecules, but the numbers undercut it. Only around 0.2 percent of the linoleic acid you eat ever converts to arachidonic acid, and when researchers feed people more linoleic acid and measure their inflammatory markers, the markers do not rise. The controlled human trials, the kind that can show cause rather than coincidence, do not find the fire the theory predicts.

The other loud claim is that seed oils cause heart disease, and people lean on two things, the old trials and the timing. The famous trials from decades ago that seemed to indict these fats were muddied, because the margarines they fed people were loaded with trans fat, the artery-damaging fat from the trans fat post, so the harm gets pinned on linoleic acid when the trans fat is the better suspect. The timing argument, that heart disease climbed as seed oil use climbed, runs into a wall when you measure people directly, because those with the highest linoleic acid intake and the highest blood levels tend to have lower heart disease risk, not higher. You can dislike how the oil is made and still admit that the body of human evidence does not show it driving heart attacks.

The thing you should be scared of instead

If linoleic acid is not lighting the fire and not clogging the arteries, what was climbing alongside it for the last century? The answer is sugar, refined flour, and ultra-processed food engineered to be overeaten. Those are the things that drive insulin resistance, fatty liver, obesity, and the slow metabolic breakdown under most modern disease, and they rose hand in hand with seed oils because they are all pieces of the same industrial diet. Seed oils ride shotgun in nearly every ultra-processed product there is, which is the real reason high seed oil intake tracks with bad health. It is a marker of a diet full of the things that hurt you.

The danger was never one fatty acid. It was a way of eating built on cheap, engineered, hyper-palatable food, and seed oils are one ingredient in it and one signpost pointing at it. Cut the ultra-processed food and the sugar, and the seed oils mostly leave on their own, because they were riding in on that food the entire time.

What to do about it

Stop frying in seed oils, since that is where the real damage happens, and cook in the stable fats from the last several posts instead, the tallow and butter and the rest. Pour off the canola and dress your food in olive oil or avocado oil. Past that, do not lose sleep over the linoleic acid in a restaurant salad dressing while a sugary soda sits next to it, because that is guarding the window while the door stands wide open. The harm in the soda is the sugar, not the bubbles, and whether the diet version carries real risks of its own is a separate and far less settled question.

Keep the whole food separate from the factory oil in your head, too. The linoleic acid in walnuts and sunflower seeds comes wrapped in fiber, antioxidants, and vitamin E that protect it, in amounts a body has always handled. Nobody got sick on walnuts. They got sick on the extracted, bleached, deodorized oil poured into everything, and on the sugar and processed food it travels with.

The corruption, and the way back

We took the fats that came off animals and out of olives, the ones people cooked with for thousands of years, and replaced them with an oil that has to be run through a chemical plant and deodorized before anyone can stand to eat it. Then we got frightened of the wrong part, the molecule, while the real harm, the processing and the ultra-processed food it lives in, went mostly unnamed. Evil does not invent new food. It corrupts what was already good and sells the corruption back to us, and it is content to let us argue over the wrong detail while it works.

The way back is the way back to real food. Cook in fats that come from somewhere you can picture, an animal or an olive or a simple press, and let the plainness of a thing be the signal. If you cannot tell what something is made of or how it was made, that earns more suspicion than any single fatty acid does.

Not every bottle of oil is a factory product, though. Some are pressed simply and carefully and have every right to be in your kitchen, and telling those from the rest comes down to how they are made and what the label is really saying. That is where we go next.

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