If you have spent any time in the MAHA or real food space you have heard one phrase repeated constantly — get seed oils out of your diet. But what are seed oils exactly, why are they so widely used, and what is the actual evidence that they are causing harm? This guide answers all of it plainly so you can make an informed decision about what goes into your kitchen and your body.
What Are Seed Oils?
Seed oils are vegetable-based oils extracted from the seeds of plants — not from the flesh or fruit, but specifically from the seed. The most common seed oils found in processed food and restaurant kitchens today are canola oil, soybean oil, sunflower oil, safflower oil, corn oil, cottonseed oil, grapeseed oil, and rice bran oil. You will also see them listed on ingredients labels as "vegetable oil" — a catch-all term that almost always means a blend of the cheapest seed oils available.
These oils are extraordinarily high in polyunsaturated fatty acids (PUFAs), particularly omega-6 linoleic acid. That distinction matters enormously, as we will explain below.
How Are Seed Oils Made?
This is where the story gets uncomfortable. Unlike olive oil — which is made by simply pressing olives — seed oils require an intensive industrial extraction process to produce. Seeds like soybeans and rapeseeds (canola) contain relatively little oil and it cannot be pressed out mechanically in meaningful quantities. Instead the seeds are:
- Heated to extremely high temperatures that immediately begin oxidising the fragile PUFAs
- Treated with petroleum-based chemical solvents like hexane to extract the remaining oil
- Degummed, refined, bleached, and deodorised to remove the rancid smell that results from the extraction process
- Packaged in clear plastic bottles and sold as a neutral cooking oil
The end product is a highly processed industrial fat that did not exist in any human diet before the 20th century. As documented extensively by the Weston A. Price Foundation, traditional populations around the world cooked exclusively in animal fats, olive oil, and coconut oil — never in industrially extracted seed oils.
Why Are Seed Oils Bad for You?
There are three primary mechanisms through which seed oils cause harm.
1. Excessive Omega-6 Linoleic Acid
Human beings evolved eating a diet with a roughly 1:1 ratio of omega-6 to omega-3 fatty acids. The modern Western diet, dominated by seed oils, has pushed that ratio to somewhere between 15:1 and 20:1 in favour of omega-6. This imbalance is strongly associated with chronic inflammation. Research indexed on PubMed links elevated omega-6 consumption to increased markers of systemic inflammation — the root driver of heart disease, obesity, type 2 diabetes, and autoimmune conditions.
2. Oxidation and Toxic Byproducts
PUFAs are chemically unstable. When exposed to heat — which happens during the extraction process and again when you cook with them — they oxidise and break down into toxic compounds including aldehydes, 4-hydroxynonenal (4-HNE), and acrolein. These compounds are cytotoxic, meaning they damage cells. A single meal cooked in vegetable oil at high heat generates measurable quantities of these compounds according to studies published on Healthline and in peer-reviewed lipid research journals. Ancestral fats like butter, ghee, and tallow are saturated and therefore chemically stable — they do not oxidise under normal cooking temperatures.
3. They Incorporate Into Cell Membranes
This is the mechanism most people are not aware of. Dietary fats do not just pass through your body — they are incorporated into your cell membranes. When you eat large quantities of linoleic acid from seed oils over months and years, that unstable PUFA becomes part of the structural fabric of your cells. This makes your cell membranes more vulnerable to oxidative damage and disrupts normal cellular signalling. The half-life of linoleic acid in human adipose tissue is approximately two years — meaning the seed oils you ate two years ago are still literally part of your body today.
Why Are Seed Oils in Everything?
Cost. Seed oils are among the cheapest fats on earth to produce at industrial scale. Soybean oil in particular is a byproduct of the soy protein industry — the oil was essentially a waste product until food manufacturers found a use for it. The shift away from traditional cooking fats like lard and butter toward vegetable oils in the mid-20th century was driven by a combination of flawed nutritional science, aggressive lobbying by the vegetable oil industry, and the economic incentive to use the cheapest available ingredients. The result is that seed oils now appear in approximately 80% of processed foods on supermarket shelves.
What Should You Cook With Instead?
The good news is that replacing seed oils is straightforward. Every cuisine in the world cooked in real fats before industrial seed oils existed — and those fats are still available today. The MAHA recipes on this blog use exclusively:
- Butter — for everyday cooking, sauces, and baking
- Ghee — clarified butter with a higher smoke point, ideal for high-heat cooking
- Beef tallow — rendered beef fat, extraordinarily stable at high heat, incredible for roasting and frying
- Lard — rendered pork fat, the traditional fat of European and Latin American cooking
- Coconut oil — saturated fat from tropical tradition, stable and flavourful
- Extra virgin olive oil — for low-heat cooking, dressings, and Mediterranean dishes
For a complete breakdown of each fat, how to cook with it, and its nutritional profile see the detox recipes guide and our full MAHA butter coffee post which walks through why fat quality changes everything even in your morning drink.
The Simple Rule
If an oil requires a factory to make it, do not cook with it. If it can be made by pressing, churning, or rendering a whole food ingredient, it belongs in your kitchen. That single principle eliminates every seed oil and keeps every ancestral fat. It is the foundation of everything cooked in Savannah Ryan's Savor cookbook series — 13 global recipe books, zero seed oils, built entirely on the fats human beings have cooked with for thousands of years.
Follow The Kitchen Foodie for seed oil free recipes from Africa, Hawaii, India, the Mediterranean, Asia and beyond.
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