Reading · Ancestral Healing

A hundred years ago, the oil in your kitchen cupboard was a waste product that cotton mills could not figure out how to get rid of.

Today it is in almost everything you eat, and almost nobody stopped to ask how that happened.

This is one of the strangest stories in the history of food, and it has been hiding in plain sight. Within roughly a century, the fats that human beings had cooked with for thousands of years, butter and tallow and lard and olive oil, were pushed almost entirely out of the Western diet and replaced with a family of industrially extracted oils that had never before been part of any human diet anywhere on earth. It was the single largest change to the composition of our food in recorded history, it happened in the space of a few generations, and it was carried out with the full endorsement of the health authorities of the day.

That endorsement is worth remembering, because the same authorities also told a generation that margarine was healthier than butter. They were wrong about that, catastrophically and for decades, and the trans fats they recommended have since been driven out of the food supply as a recognised danger. The people who got that so badly wrong are the same people who assured us that the oils replacing our traditional fats were an improvement.

So let us look at this properly. What these oils actually are, and how they are made. What the evidence says they do inside the body, including where that evidence is strong and where it is still argued over. What to cook with instead, in practical detail. And the remarkable, almost unbelievable story of how a byproduct of the cotton industry came to line the shelves of every supermarket on the planet.

Let us begin.

The name gives away more than most people notice. Seed oils are exactly what they sound like: oils extracted from the seeds of plants. And that single fact is the beginning of the whole problem, because seeds are not designed to give up their oil easily.

Consider the contrast. An olive is a soft fruit with a high oil content in its flesh. You can crush olives between two stones and oil runs out. The same is broadly true of coconut, avocado, and palm fruit. Human beings have been pressing oil from these for thousands of years using nothing more complicated than physical force, and the result is a food you could recognise as food.

Now consider a soybean, a rapeseed, a cotton seed, or a grape seed. These are small, hard, and comparatively low in oil. You cannot meaningfully press oil out of them by hand, and no traditional culture ever did.

To get oil out of a seed at commercial scale requires industrial machinery and industrial chemistry, and that is precisely how it is done.

The oils in question.

The family usually meant by the term includes soybean oil, corn oil, canola oil (which is rapeseed), cottonseed oil, sunflower oil, safflower oil, grapeseed oil, and rice bran oil. Peanut oil sits at the edge of the category. In practice you will most often encounter them hiding behind the wonderfully vague label “vegetable oil,” which tells you nothing about what plant it came from and is usually soy or canola.

How they are actually made.

This is the part that changes how most people feel about the bottle in their cupboard, and it is worth walking through step by step.

The seeds are cleaned, heated, and crushed or rolled to release what oil they will give up under pressure. That alone leaves a great deal of oil behind in the seed meal, so the crushed material is then washed in a solvent, most commonly hexane, which is derived from petroleum. Hexane dissolves the remaining oil out of the seed. The solvent is then evaporated off and recovered for reuse, and while regulators consider residual levels to be within acceptable limits, the fact remains that the extraction of your cooking oil involves bathing plant matter in a petroleum solvent.

What comes out at that stage is a crude oil that is dark, cloudy, strong smelling, and frankly not something anyone would want to eat. So it goes through a further sequence of treatments known in the industry as refining, bleaching, and deodorising, which is where the shorthand RBD comes from.

Degumming removes phospholipids. Then the oil is treated with caustic soda to neutralise free fatty acids. Then it is passed through bleaching clay to strip out colour and remaining impurities, which also removes much of whatever natural antioxidant content survived. Then comes deodorising, in which the oil is subjected to steam under vacuum at temperatures often above 200 degrees Celsius in order to strip out the volatile compounds responsible for the smell and taste.

Pause on that last step, because it tells you something important. The oil has to be deodorised because otherwise it smells rancid. The industrial process does not prevent the oil from degrading. It removes the evidence that it has. What emerges at the end is a clear, neutral, almost flavourless liquid that gives the impression of being clean and pure precisely because everything that would have told you otherwise has been chemically removed.

Compare that to butter, which is churned cream, or tallow, which is rendered fat, or extra virgin olive oil, which is pressed fruit. One of these categories is food processing. The other is chemical manufacturing.

What is actually in them.

Now to the chemistry, because this is where the health arguments live.

Fats are made of fatty acids, and fatty acids differ in how many double bonds they contain. Saturated fats have none, which makes them chemically stable and resistant to damage from heat and oxygen.

Monounsaturated fats, such as the oleic acid that dominates olive oil, have one.

Polyunsaturated fats have two or more, and each additional double bond is another point of chemical vulnerability, another place where the molecule can be attacked by heat, light, and oxygen.

Seed oils are overwhelmingly polyunsaturated, and specifically they are extraordinarily high in one particular polyunsaturated fatty acid: linoleic acid, an omega 6 fat.

The numbers are worth seeing plainly. Safflower oil can be around 70 to 75 percent linoleic acid. Sunflower oil is commonly around 60 to 70 percent. Corn oil sits around 50 to 55 percent. Soybean oil around 50 percent. Cottonseed oil somewhat lower. Compare those figures to olive oil at roughly 10 percent, lard at around 10 percent, and butter at around 2 to 3 percent.

This is the crux of it. Linoleic acid is an essential fatty acid, meaning your body genuinely requires some of it and cannot make it. Nobody disputes that. The question is one of quantity, because the amount now present in the average Western diet is entirely without historical precedent. Human beings obtained small amounts of linoleic acid from nuts, seeds, eggs, and animal fats for the whole of our evolutionary history. We now pour it over everything, in quantities our ancestors could not have obtained if they had tried.

That change in quantity, combined with the chemical fragility of the molecule itself, is the foundation of everything in the next chapter.

Let me set the framing honestly before we start, because this topic attracts a great deal of noise from both directions and neither extreme will help you.

You will find people online claiming that seed oils are single handedly responsible for every chronic disease of the modern world. You will also find people insisting there is nothing whatsoever to discuss and that anyone raising the question is a crank. Both positions are unserious. The truth is more interesting than either, and it is strong enough on its own terms without exaggeration.

Here is what actually holds up.

This is the mechanism that deserves the most attention, and it follows directly from the chemistry in the last chapter.

Polyunsaturated fats are fragile by nature. Every double bond is a site vulnerable to attack by oxygen, and when a polyunsaturated fatty acid is oxidised it does not simply become inert. It breaks apart into a cascade of reactive breakdown products, a process called lipid peroxidation. Among the compounds formed are aldehydes, including 4 hydroxynonenal, malondialdehyde, and acrolein.

These are not benign. They are reactive molecules capable of damaging proteins, cell membranes, and DNA, and they have been studied for decades in exactly that context. This is not fringe science. It is established biochemistry.

Now consider what we do with these oils in practice. We heat them. We fry in them. Restaurants and fast food operations heat the same oil repeatedly, for hours, sometimes for days, and every heating cycle generates more of these breakdown products. Research measuring aldehyde formation in repeatedly heated cooking oils has found concentrations that are far from trivial.

There is a bitter irony here that deserves naming. Refined seed oils are often recommended for high heat cooking because they have a high smoke point. But smoke point measures when an oil visibly begins to smoke. It does not measure oxidative stability, which is a different property entirely.

An oil can have a high smoke point and still be forming harmful oxidation products well before it smokes, because the fragility comes from the double bonds, not from the temperature at which the oil becomes visibly distressed. By the measure that actually matters, a stable saturated or monounsaturated fat outperforms a polyunsaturated one, regardless of what the smoke point chart says.

There is a second dimension to this that reaches further into the body. Linoleic acid is the most abundant fatty acid in the LDL particles circulating in your blood, and oxidised linoleic acid breakdown products have been identified in atherosclerotic plaque. Researchers have taken this seriously enough to investigate whether the oxidation of linoleic acid within LDL is a meaningful step in the development of arterial disease. This is an area of active study rather than settled conclusion, but it is a real line of scientific inquiry and not something anyone invented on the internet.

Omega 6 and omega 3 fats are not opponents exactly, but they are competitors, and understanding how gives you the second major mechanism.

Both families are converted by the body into signalling molecules that regulate inflammation, and both families rely on the same enzymes to make that conversion. That means they compete for the same machinery. When omega 6 is present in vast excess, it monopolises those enzymes and crowds out the processing of omega 3.

The two families also produce different downstream signals. The compounds derived from omega 6 tend, broadly, to promote inflammation, which is a necessary and useful function in its proper place. The compounds derived from omega 3, including a family of molecules called resolvins, are involved in resolving inflammation and bringing it to a close. A body swimming in omega 6 and starved of omega 3 is a body better equipped to start inflammation than to finish it.

The scale of the shift is what makes this compelling. The ratio of omega 6 to omega 3 in ancestral human diets is generally estimated to have been somewhere in the range of 1 to 1 up to about 4 to 1. Estimates for the modern Western diet commonly land around 15 to 1 or 20 to 1, and sometimes higher. And this is not merely a dietary calculation on paper. Studies measuring the linoleic acid content of human body fat over the twentieth century have documented a substantial increase, because the fats you eat are literally incorporated into your tissues. Your body composition has changed to reflect what came out of the bottle.

Given that chronic low grade inflammation is the common thread running through cardiovascular disease, metabolic dysfunction, autoimmunity, and neurodegeneration, a dietary change that systematically tilts the body’s inflammatory balance is not a small matter.

Here is a mechanism that receives less attention than it deserves. The fatty acids you consume are not only burned for fuel. They are built into the membranes of your cells and of your mitochondria, the structures that produce your energy.

A membrane rich in polyunsaturated fats is a membrane that is more susceptible to peroxidation, and mitochondrial membranes are situated in an environment where reactive oxygen species are constantly produced as a byproduct of energy generation. Some researchers argue that shifting membrane composition toward higher polyunsaturated content affects mitochondrial function, metabolic flexibility, and insulin sensitivity.

Be clear about the standing of this argument. It is a mechanistic hypothesis with a plausible biochemical basis and some supporting evidence, rather than a settled conclusion. But it is a serious line of thinking, and it points at something the calorie counting approach to nutrition entirely misses: that fats are not just fuel, they are structural material, and what you build your cells out of matters.

This argument gets overlooked constantly, and it may be one of the most important of all.

Every calorie of seed oil that entered the diet displaced a calorie of something else, and what it displaced was butter, tallow, lard, ghee, and cold pressed olive oil. Those fats were not simply energy. They were carriers of nutrition.

Butter from pastured animals carries vitamin A in its active form, vitamin D, vitamin E, and vitamin K2, the vitamin that directs calcium into your bones and teeth rather than into your arteries. It carries butyrate, which nourishes the cells lining your colon. Pastured lard is one of the better food sources of vitamin D. Extra virgin olive oil carries polyphenols including oleocanthal, which has been studied for its anti inflammatory action, along with substantial vitamin E.

Refined seed oils, by the time they have been degummed, neutralised, bleached, and deodorised, carry almost none of this. The processing that makes them shelf stable and neutral tasting strips out most of what little micronutrient content the crude oil had. So the swap was not merely one fat for another. It was a nutrient dense fat for a nutrient stripped one, repeated billions of times a day across an entire civilisation.

There is one more point that is almost impossible to separate from the rest, and honesty requires acknowledging it.

Seed oils are not just something people cook with at home. They are a foundational ingredient of ultra processed food. They are in the crisps, the biscuits, the sauces, the dressings, the ready meals, the fried food, the baked goods, and the snacks. They are there because they are cheap, neutral, and stable, which makes them the ideal industrial fat.

This means that in the real world, high seed oil consumption travels together with high consumption of refined flour, added sugar, and industrial additives. Untangling the effect of the oil from the effect of the entire ultra processed food matrix is genuinely difficult, and anyone who tells you it has been cleanly achieved is overstating the case.

But notice that this cuts in a useful direction rather than a comforting one. If seed oils are inseparable from ultra processed food, then avoiding them means avoiding ultra processed food, and that is an unambiguous good regardless of how the isolated question is eventually resolved.

The practical conclusion holds either way.

Fairness demands this section, and including it will make you harder to dismiss rather than easier.

Major health bodies, including cardiology associations and dietary guideline committees worldwide, continue to recommend polyunsaturated vegetable oils as part of a heart healthy diet, on the basis that replacing saturated fat with polyunsaturated fat lowers LDL cholesterol. That is a real finding and it is why the recommendation exists.

The counterargument is that lowering LDL cholesterol is a surrogate marker, and the trials that tested whether this substitution actually reduces deaths have produced a genuinely mixed picture. Several of the mid twentieth century trials in this area, including the Sydney Diet Heart Study and the Minnesota Coronary Experiment, produced results that were either unfavourable or that went unpublished for decades, and their later reanalysis caused real argument in the field. Other work has suggested benefit. The picture that emerges from the trial literature as a whole is considerably less tidy than the confident public messaging would suggest.

So here is the honest position, and it is a strong one. The claim that seed oils are the single cause of modern chronic disease goes beyond what the evidence supports, and repeating it will get your genuine concerns dismissed by anyone who checks. But the claim that these oils are a well studied, thoroughly settled, obviously beneficial part of the human diet is equally unsupportable. What we actually have is an unprecedented dietary change, made on the basis of a hypothesis that has since become contested, involving chemically fragile molecules that demonstrably form toxic compounds when heated, which displaced nutrient dense traditional fats and which arrive in our diet embedded in ultra processed food.

You do not need to prove more than that to justify getting them out of your kitchen.

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This is the practical chapter, and it should feel like a relief rather than a restriction, because the replacements are more delicious than what they replace. Every fat below is one that human beings have cooked with for centuries or millennia, and every one of them tastes of something.

The organising principle is simple. For heat, you want stability, which means saturated and monounsaturated fats. For flavour and for raw use, you want the polyphenol rich pressed fruit oils. Match the fat to the job.

Rendered beef fat is the single best choice for anything involving serious heat. It is predominantly saturated and monounsaturated, which makes it remarkably resistant to oxidation, and it produces a crispness in fried food that nothing else quite matches. There is a reason chips fried in tallow taste the way they do, and a reason so many people remember fast food tasting better before the industry switched away from it in 1990.

You can buy it, or you can render it yourself for almost nothing. Ask a butcher for beef fat trimmings or suet, chop them small, place them in a heavy pot over the lowest possible heat with a splash of water to prevent scorching, and let them melt slowly over a few hours. Strain the liquid fat through muslin into jars. It keeps for months in the fridge and a long time even in the cupboard, because saturated fat does not readily go rancid. This is genuinely ancestral cooking, it costs a fraction of a bottle of oil, and it uses a part of the animal that would otherwise be discarded.

Butter from grass fed animals is a nutritional powerhouse as well as a pleasure, delivering vitamins A, D, E, and K2 along with butyrate. Its one limitation is that the milk solids in it will brown and then burn at moderate temperatures, which restricts it to gentler cooking.

Ghee solves that problem entirely. Simmer butter gently until the milk solids separate out and toast golden at the bottom, then strain off the clear golden fat. What remains is almost pure butterfat, with a much higher smoke point, excellent stability, a beautiful nutty flavour, and none of the dairy proteins that some people struggle with. It also keeps for months without refrigeration. Sacred in traditional Indian cooking for thousands of years, and one of the most useful fats you can have on the shelf.

Extra virgin olive oil is pressed fruit, and it is one of the most well evidenced foods in the entire nutritional literature, sitting at the centre of the Mediterranean way of eating. It brings polyphenols, oleocanthal, vitamin E, and a dominant monounsaturated fatty acid profile.

Now let me correct a persistent myth, because it costs people the use of an excellent fat. You will often hear that olive oil should never be heated. This is largely wrong. Because it is mostly monounsaturated, with only one double bond per molecule, olive oil is considerably more resistant to oxidation than any polyunsaturated seed oil, and research examining its behaviour under cooking conditions has found it to hold up well. Its polyphenol content also provides built in antioxidant protection. It is perfectly suitable for sautéing, roasting, and moderate heat cooking, and it is superb raw.

Buy it in dark glass, keep it away from heat and light, and be aware that the olive oil market has a well documented adulteration problem, so buying from a producer or brand you trust matters.

Lard from pastured pigs is an excellent, stable cooking fat, and it has a particular gift for pastry, where it produces a texture that nothing else replicates. Pastured lard is also a meaningful food source of vitamin D, since pigs raised outdoors in sunlight accumulate it in their fat.

Duck and goose fat are worth seeking out for roasting vegetables, particularly potatoes, and both are traditional treasures of French cooking. Save the fat that renders out whenever you roast a duck or a chicken, keep it in a jar in the fridge, and use it. Your ancestors would be baffled by the idea of pouring it away.

Coconut oil is among the most saturated fats available, which makes it extremely resistant to heat damage. It contains medium chain triglycerides, which the body handles differently from longer chain fats. Its distinct flavour makes it better suited to some dishes than others, and refined coconut oil is more neutral if you want the stability without the taste.

Avocado oil is pressed from fruit flesh, is high in monounsaturated fat, and has a high smoke point, which makes it useful. The caveat is significant though: independent testing has repeatedly found a large proportion of avocado oil on the market to be adulterated with cheaper oils or to be rancid before it reaches the shelf. It is a good fat in principle and a risky purchase in practice, so buy carefully from reputable sources.

Walnut, macadamia, sesame, and similar cold pressed oils are lovely for drizzling and dressing, where their flavour shines and they are never exposed to heat.

Keep them refrigerated, buy them small, use them quickly, and do not cook with them.

To make this simple:

Deep frying and high heat searing: tallow, ghee, coconut oil, lard.

Roasting: duck fat, goose fat, tallow, lard, olive oil.

Sautéing and everyday pan cooking: butter, ghee, olive oil.

Baking: butter, lard for pastry, coconut oil where the flavour suits.

Dressings and raw finishing: extra virgin olive oil, cold pressed nut oils.

The names to watch for on ingredient lists are soybean oil, canola oil, corn oil, cottonseed oil, sunflower oil, safflower oil, grapeseed oil, rice bran oil, and the deliberately uninformative “vegetable oil.” They appear in a remarkable range of products, including many marketed as healthy: mayonnaise, salad dressings, hummus, nut butters, tinned fish, crackers, bread, chocolate, and infant formula.

One honest nuance worth knowing about. You will increasingly see high oleic sunflower and safflower oils. These have been bred to be much higher in monounsaturated oleic acid and much lower in linoleic acid, which does give them a considerably better oxidative profile than their conventional counterparts. They are still industrially refined, but they are a legitimate improvement, and worth knowing about when a whole food fat is not on offer.

The largest single lever available to you, though, has nothing to do with labels. Almost every restaurant, takeaway, and fast food operation on earth cooks in seed oils, usually reused repeatedly at high temperature, which is the worst case scenario described in the previous chapter. Cooking at home is therefore not merely a nice habit. It is the most effective step available for reducing your exposure, and it happens to be the same step that fixes most other things about the modern diet at the same time.

There is nothing wrong with asking a restaurant what they cook in. A growing number now use butter, olive oil, or tallow and are proud to say so.

Now for the story, and it is a remarkable one. If someone invented this as fiction it would be dismissed as too neat.

In the nineteenth century, the American cotton industry had a problem. Cotton ginning produced enormous quantities of cotton seed as waste, piling up around mills with no use and no market. Some was used as low grade fertiliser or animal feed. Much was simply dumped, and it was considered a nuisance.

Then chemists worked out that oil could be extracted from those seeds and refined into something that looked and behaved like an edible fat. Almost immediately it found its first commercial use, and that use tells you a great deal: cottonseed oil was employed as a cheap adulterant, quietly blended into lard and olive oil to stretch them and increase profit. Before it was ever a food in its own right, it was a way of diluting real food without telling anyone.

It also had industrial applications. Rapeseed oil, the ancestor of modern canola, was valued as a machine lubricant, notably for steam engines, long before anyone proposed putting it on a salad.

The pivotal turn came from a soap and candle manufacturer in Cincinnati named Procter and Gamble, which bought cottonseed oil as a raw material for its products. Then electric lighting arrived and the candle business began to die, leaving the company with expertise in processing an oil and a shrinking market for it.

Their solution was hydrogenation, a process that forces hydrogen into the oil to make it solid at room temperature. In 1911 they launched the resulting product as Crisco, a name shortened from crystallised cottonseed oil, and sold it as a substitute for lard.

The marketing campaign that followed was genuinely brilliant and worth studying, because its logic still shapes how we think about fat. Crisco was presented as modern, clean, pure, and scientific, in explicit contrast to animal fat, which was framed as old fashioned and somehow unwholesome. Procter and Gamble produced free recipe books built entirely around the new product and distributed them widely to households, so that a generation of cooks learned to cook with it as the default. The company also promoted it to Jewish households, pointing out that unlike lard or butter it was neither meat nor dairy and could be used freely under kosher rules.

None of this was based on any evidence that the new product was better for human health. There was no such evidence, because nobody had looked. It was a manufacturer solving a commercial problem, and it worked spectacularly.

By the middle of the twentieth century, heart disease had become the leading cause of death in Western countries and researchers were urgently seeking an explanation. The hypothesis that came to dominate, associated most closely with the American physiologist Ancel Keys, held that dietary saturated fat raised blood cholesterol and that blood cholesterol caused heart disease. It followed logically that replacing saturated animal fat with polyunsaturated vegetable oil should protect the heart.

Keys was a formidable and persuasive figure, and his Seven Countries Study became enormously influential. Critics have long argued that the countries examined were selected in a way that favoured the hypothesis and that the study design could not establish causation, and that argument continues. But at the time, the diet heart hypothesis swept the field.

In 1961 the American Heart Association issued guidance recommending that people replace saturated fat with polyunsaturated vegetable oils. It was one of the most consequential dietary recommendations of the century.

And here is a piece of history that deserves to be more widely known. The American Heart Association had been a small professional society until 1948, when a national radio programme sponsored by Procter and Gamble ran a fundraising campaign that raised over one and a half million dollars for the organisation, transforming it overnight into a major national body with the resources to shape public opinion. The company that had invented Crisco helped fund the rise of the institution that would go on to recommend replacing animal fat with vegetable oil.

That is not proof of a conspiracy, and it should not be presented as one. Many people involved were sincere and were doing their best with the evidence they had. But it is a documented fact about how institutional influence works, and it belongs in the story.

The recommendation moved from professional guidance to state policy over the following two decades. The McGovern Committee’s Dietary Goals for the United States in 1977 and the first official Dietary Guidelines in 1980 both instructed the population to reduce saturated fat and cholesterol. Similar advice followed across the Western world.

The effect on what people actually ate was dramatic. Butter consumption in the United States collapsed over the twentieth century while margarine consumption soared. Soybean oil consumption rose by an almost incomprehensible multiple, with some estimates putting the increase at more than a thousandfold across the century. Lard and tallow largely vanished from commercial kitchens. In 1990, following a sustained public campaign against animal fat, major fast food chains switched from frying in beef tallow to frying in vegetable oil, and one of the last mainstream holdouts fell.

Now comes the part of this story that should inform how we treat current dietary advice.

The hydrogenation that made these oils solid and shelf stable created artificial trans fats. Margarine, the product a generation was urged to spread on their bread instead of butter, was full of them.

Over subsequent decades the evidence accumulated that industrial trans fats were genuinely harmful to cardiovascular health, and it eventually became overwhelming. Trans fats have now been effectively banned or phased out of the food supply across much of the world, recognised as a substance that should never have been in food at all.

Sit with the implications of that. For decades, the official public health position, backed by the most respected institutions in medicine, was that people should stop eating butter and start eating a manufactured product that we now know was actively damaging their hearts. The advice was not merely imperfect. It was inverted. And it took the better part of half a century to correct.

This is the honest reason to approach current confident assurances with caution. Not because scientists are villains, but because the institutional record on exactly this question is genuinely poor, and because the same commercial incentives that shaped the original advice have never gone away.

Finally, the reason seed oils remain everywhere despite the growing questions has less to do with health than with money.

Soy and corn are heavily subsidised commodity crops grown at enormous scale, and their oils are effectively byproducts of that system, which makes them extraordinarily cheap. They are neutral in flavour, so they can be used in any product without interfering with its taste. They are shelf stable after refining, which suits long distribution chains and long shelf lives. And they are liquid at room temperature and easy to handle in industrial processing.

For a food manufacturer, this combination is close to ideal. There is no comparable substitute at that price. Butter, tallow, and olive oil all cost considerably more, taste of something, and behave less conveniently. The reason your biscuits and crisps and sauces are made with these oils is not that anyone determined they were the healthiest option. It is that they are the cheapest fat that will do the job, and the health question was settled decades ago by institutions that turned out to be wrong about margarine.

The Seed Oil Deception

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