The History of Seed Oils and Why They’re Bad for You
Comparing Early 1900s to Today: A Century in Review
In the early 1900s, the leading causes of death for Americans were infectious diseases, such as pneumonia, tuberculosis, influenza, and gastrointestinal infections. Outbreaks of waterborne illnesses, poor sanitation, and the lack of vaccines and antibiotics contributed significantly to early mortality.
Over time, with advancements in medicine and improvements in sanitation and water quality, many of these once-common infectious diseases were either dramatically reduced or eliminated.
Yet, what seemed to mark the beginning of a golden age of health had given way to a modern public health crisis.
Chronic diseases, such as coronary artery disease, strokes, hypertension, brain and autoimmune diseases, diabetes, obesity, et al., were rare among Americans—suffice it to say, in the late 1800s to the early 1900s, chronic diseases were almost nonexistent. Yet, today, Americans face an unprecedented increase in chronic diseases.
To put this in perspective, let’s compare the numbers:
In 1900 practically no one was overweight, and only about 1 out of every 100 Americans was obese (approximately 1.2%),* compared to an obesity rate of 42.5% in 2018, with projections suggesting an increase to 48.9% by 2030.*
In 1900 cancer accounted for about 1 in 17 deaths (5.8%). Today’s cancer rates would have seemed impossible to doctors back then. By 2010, cancer was responsible for approximately 1 in 3 deaths (31.1%).*
In 1911 heart attacks were so rare that most doctors had never seen one. In fact, there were fewer than 10 documented cases in all the medical books of that time. Most physicians didn't even know what a heart attack was since the first documented heart attack in the U.S. occurred in 1912.*
Diabetes was so uncommon that it affected fewer than 3 out of 100,000 people (0.0028%). In contrast, as of 2024, about 14.7% of adults in the United States (aged 18 and older) have diabetes, according to the CDC,* which amounts to roughly 38 million people.
Brain diseases such as Alzheimer's disease and dementia were completely unknown. For example, there were only five documented cases of Alzheimer's disease worldwide during the early 20th century—one in 1908 and four in 1910. Today, Alzheimer’s affects 55 million people around the world.
Autoimmune diseases, like multiple sclerosis, lupus, and Type 1 diabetes—where the body’s immune system attacks itself—were either very rare or possibly nonexistent.*
Uncovering the Change and Underlying Cause
A quick Google search for “Reasons for chronic disease and health decline in US over past century” offers the following: Smoking, Physical Inactivity, Obesity, Poor Diet, Socioeconomic Disparities, Access to Healthcare, Aging Population, and Exposure to Toxins.
While it’s true that many of these factors impact health, most of the reasons listed above are questionable based on timeline inconsistencies, logical fallacies (confusing symptoms with causes), or unrelated and misleading information—remember, correlation does not equal causation.
What we’re searching for is a “why”—a factual reason or cause. The best explanation should be simple, direct, require the least assumptions, and be supported by statistical evidence.
Among the reasons listed above, there is one that stands out, necessitating deeper investigation: Poor Diet.
The Surge of Processed and Ultra-Processed Foods
To analyze the subject of Poor Diet more closely, let’s look at what exactly changed in our diet—and specifically, what changed at or just prior to the rise of chronic diseases.
The most reliable method of measuring any activity is with statistics. Provided the data is from a credible source, statistics also offer the most compelling evidence—as you will see.
According to data collected from the USDA Economic Research Service, U.S. Dept Commerce, and U.S. Census, the most significant change in the American diet over the past century has been the sharp increase in, and heavy reliance on, processed and ultra-processed foods.
Animal & Plant Foods vs. Processed Foods, U.S. (1865 vs. 2009)
Year 1865
Year 2009
Now, let’s discover what Americans were eating around 1900, and perhaps more importantly, what foods were absent from their diets?
Culinary researcher Lynne Olver* noted that most Americans at that time lived in agricultural communities, often raising their own livestock and poultry—mainly for eggs rather than meat. People commonly grew vegetables and herbs, and wild game from hunting and fishing supplemented their diets. Nearly all food was home-cooked from scratch. By 1908, daily staples included wheat and other grains (oats, rice, corn), which made up about 37% of the diet. Potato dishes appeared frequently, often prepared with butter or lard.
To isolate what Americans were not eating during this period, we first have to understand what processed foods are. They are essentially defined as foods containing added sugars, refined grains (mostly white wheat flour), and vegetable oils (generally referred to as seed oils).
The Birth of Vegetable Oils: How They Entered Our Food Supply
In 1900 processed foods were rare, and vegetable oils were nearly unheard of. Before 1865, the term "vegetable oils" didn't exist, and most people had never seen or tasted them. If edible oils were used, they were mainly olive oil, with small amounts of sesame, peanut, coconut, or palm oils in some regions.
The origins of vegetable oils, even though these oils aren’t made from actual vegetables, surprisingly trace back to chemists in soap factories, not foods.
In the 1890s, Procter & Gamble faced a shortage of beef tallow for making soap, so they turned to cottonseeds—a textile byproduct. Although cottonseeds had little value in foods because they contained a harmful compound, P&G discovered that when cottonseeds were processed and the oil was refined, most of the compound was removed.
This oil was first used as lamp fuel and lubricant for machinery. However, once petroleum took its place for lighting, meatpackers started mixing cottonseed oil with animal fats to stretch supplies, and it was sometimes added to olive oil. After these adulteration practices became public, demand for cottonseed oil dropped, creating a surplus and making it cheap and readily available.
Ignoring the negative publicity surrounding cottonseed oil, P&G spotted a chance to purchase it cheaply and substitute it for pricey tallow. By 1907, with the help of German chemist Edwin C. Kayser, they learned how to turn liquid cottonseed oil into a solid fat by adding hydrogen atoms—a process called hydrogenation, which you’ll learn more about below.
At first, this hydrogenated oil was sold as ivory soap. When the process was tweaked, it produced a soft, spreadable fat that resembled lard—giving P&G the idea to introduce it as a substitute for lard. In 1911, the product was launched as Crisco. A clever marketing campaign promoted Crisco as a “clean” and “healthier” cooking fat for families. It was effective enough to make Crisco the popular choice for home cooking. And so, the Edible Oil Industry was born.
Over the next century, nearly all animal fats were replaced in household cooking. The term “vegetable oils” became increasingly popular while traditional staples like pork lard, beef tallow, and butter dropped sharply in use.
The chart below shows the shift in the consumption of fat types—from traditional animal fats (butter, lard and beef tallow) to vegetable oils (corn oil, cottonseed oil, canola oil, soy oil, sunflower oil, safflower oil, grapeseed oil, rice bran oil).
Change in Consumption of Fat Types, U.S. (Scale shows lbs/capita/year)
The Rise of Chronic Disease in Modern America
As Chris Knobbe, MD concluded in The Ancestral Diet Revolution, “Over the past eleven years, our combined research and investigations have proven one irrefutable fact: Wherever vegetable oils are introduced into populations, a massive trail of destruction follows. This includes increases in coronary heart disease (CHD), cancers, metabolic syndrome, type 2 diabetes, dementia, Alzheimer's disease, age-related macular degeneration (AMD), autoimmune diseases, and many other chronic disease conditions, many of which are proven to have increased at least thousands-of-fold, and perhaps infinitely.”
Today, approximately 60% of American adults are affected by at least one chronic illness, and 40% manage two or more ongoing conditions. These widespread health issues are responsible for the majority of the country’s $4.9 trillion annual health care spending and, according to the U.S. Department of Health and Human Services, chronic diseases make up 86% of all health care expenditures.
The charts provided below paint a shocking picture, linking the consumption of vegetable oils to heart disease, obesity, diabetes and cancer. It’s important to note that while vegetable oil consumption and rates of chronic diseases and deaths have risen in parallel, the consumption of saturated fats showed minimal change during the same period.
Vegetable Oil & Saturated Fat Compared to Heart Disease Deaths, U.S. (Scale shows grams/capita/day)
Comparison of Vegetable Oil Consumption to Obesity, Diabetes & Cancer Deaths, U.S. (Scale shows kilocalories/capita/day)
The Hidden Truth About Vegetable Oils (Seed Oils)
Note: A full glossary of terms has been provided at the end of this section. All words in bold are defined in the glossary.
Vegetable oils—also known as seed oils, edible oils, or polyunsaturated fatty acids (PUFA)—were virtually absent from American diets in 1865, but by 2009, their consumption had soared to 63% of American diets (see pie charts above). Today, seed oils are found everywhere: in salad dressings, mayonnaise, chips, crackers, restaurant fryers, and even in many so-called “health foods.”
What are Seed Oils?
When people talk about “seed oils” in everyday cooking or packaged foods, they’re usually referring to industrially processed seed oils such as soybean, canola, sunflower, safflower, and corn oil—not fruit-based oils like olive, avocado, or coconut, which are extracted from the pulp rather than the seed.
The most common seed oils in today’s food supply, often grouped under the broad label “vegetable oils” and sometimes called the “Hateful Eight” because of their negative health effects, include:
Soybean oil
Canola oil (rapeseed)
Sunflower oil
Safflower oil
Corn oil
Cottonseed oil
Rice bran oil
Grapeseed oil
These oils are inexpensive, heavily refined, and widely used in packaged snacks, baked goods, fried foods, and even “healthy” grocery items—making them difficult to avoid without careful label reading.
Why Are Seed Oils Harmful?
Vegetable oils are highly concentrated sources of omega-6 fatty acids. While it’s commonly believed that an imbalance between omega-3 and omega-6—driven by the widespread use of seed oils in our food supply—is the root cause of chronic disease, Catherine Shanahan, MD, offers a different perspective. Dr. Shanahan, a board-certified physician and renowned nutrition expert, is the author of “Dark Calories.” She emphasizes that oxidative stress from the processing of these oils, rather than the fatty acid ratio itself, is the real driver of health problems.
“The real villain is a chemical process called oxidation. Seed oils cause damage to our bodies because they promote out-of-control oxidation reactions in our body’s cells. Outside our body, oxidation reactions occur around us all the time. Fire is one common oxidation reaction, its a reaction between carbon in wood and oxygen in the air. Rusting is another, it’s oxidation reaction between iron and the oxygen in water. Sliced apples browning reveal different types of oxidation occurring in the injured apple cells… When our diet contains unhealthy seed oils, oxidation reactions in our cells can get out of control. This is how seed oils cause inflammation. Not omega-6.”
Most seed oils undergo harsh extraction and refining processes in large factories. During production, seeds are heated and crushed, breaking down delicate fats and creating toxic byproducts called lipid oxidation products (LOPs). Chemical solvents like hexane are often used to extract every last bit of oil. Even after refining aims to “clean” the oil, many nutrients and natural antioxidants are lost, while tasteless, harmful byproducts can remain.
Without these protective nutrients, the fragile fats in seed oils are vulnerable to further oxidation, both in storage and when consumed. It's these damaging toxins formed during processing—not the fats themselves—that are responsible for many health concerns.
When we eat foods containing these LOPs, they can trigger inflammation and place stress on our cells—increasing the risk for chronic diseases.
| Double Bonds | Chemical links between two carbon atoms in a fatty acid chain. The presence of double bonds makes a fat unsaturated and affects whether it is liquid or solid at room temperature. They are represented by two parallel lines (=) between atoms in structural formulas. |
| Essential Fatty Acids | Fats the body cannot make on its own—mainly omega-3 and omega-6—that must be obtained from food. |
| Fatty Acids | The building blocks of fats and oils. They are important because they help build cell membranes, support brain function, regulate inflammation, and provide the body with energy. |
| Hydrogenation | An industrial process where hydrogen is added to unsaturated fats, turning them into solid or semi-solid trans fats used in processed foods. |
| Inflammation | The body's natural immune response to injury or harmful substances. |
| Linoleic Acid | The main omega-6 fat found in seed oils. It is a type of polyunsaturated fatty acid that our bodies use to build larger molecules for important biological functions. Foods that naturally contain linoleic acid, such as certain seeds and nuts, do not cause inflammation when eaten unprocessed. The real issue arises from the oxidation of these fragile fats, not from linoleic acid itself. |
| Lipid Oxidation Products (LOPs) | Harmful compounds formed when fats, especially polyunsaturated fats, are exposed to heat or industrial processing. |
| Lipids | A group of naturally occurring molecules that are generally insoluble in water but soluble in organic solvents. Lipids play crucial roles in various biological processes, such as energy storage, cell membrane structure, and hormone synthesis. |
| Monounsaturated Fat | An unsaturated fat with one double bond, found in olive oil, avocados, and certain nuts. |
| Omega-3 | A type of polyunsaturated fatty acid found in fish, flaxseed, and walnuts, important for brain and heart health. |
| Omega-6 | A type of polyunsaturated fatty acid common in seed oils, necessary in small amounts but often consumed in excess. |
| Oxidative Stress | A harmful condition caused when the body has more damaging reactive molecules—called free radicals—than it can neutralize. This imbalance can damage fats, proteins, and DNA, contributing to disease. |
| Polyunsaturated Fatty Acid (PUFA) | Unsaturated fats with two or more double bonds, which include both omega-3 and omega-6 fatty acids. |
| Saturated Fat | A type of fatty acid that is solid at room temperature and found in animal fats and coconut oil. They are called "saturated" fats because their chemical structure is filled (or "saturated") with hydrogen atoms. In saturated fats, each carbon atom in the chain is bonded to the maximum number of hydrogen atoms possible. |
| Trans Fat | Artificially manufactured fat that alters the natural structure of unsaturated fats, linked to negative health effects and found in processed foods. |
| Triglyceride | The main form in which fat is stored in the body, made up of three fatty acids attached to a glycerol molecule. |
| Unsaturated Fat | Fats with one or more double bonds in their structure, usually liquid at room temperature, found in plants and fish. |
What Can You Do?
Here are practical steps you can take to reduce your exposure to harmful seed oil toxins and support your health:
Check Ingredients: Avoid products with seed oils—canola, corn, cottonseed, soybean, sunflower, safflower, grapeseed, and rice bran oil. Always read labels, even on items like salad dressings, snacks, and sauces.
Choose Healthier Fats: Opt for traditional fats like olive oil, avocado oil, coconut oil, beef tallow, and butter, which are less processed and more stable. Make sure the oils you buy are 100% unadulterated by checking the labels and buying from reputable brands.
Make Your Own Foods: Prepare salad dressings, sauces, and meals at home to control the oils you use.
Be Selective Dining Out: Support restaurants that use healthy cooking oils instead of seed oils, and don’t hesitate to ask what oils they use. Also, use websites and apps like Seed Oil Scout to find the best seed oil-free spots.
Swap Shelf Staples: Switch out processed foods and snacks that list seed oils in their ingredients for products made with natural fats.
Recommended Reading
If you’d like to dive deeper into the history, science, and health impacts of industrial seed oils, two highly regarded books offer a thorough exploration of this topic. Dark Calories: How Vegetable Oils Destroy Our Health and How We Can Get It Back by Catherine Shanahan, MD, uncovers the hidden role of vegetable oils in modern chronic disease. Likewise, The Ancestral Diet Revolution: How Vegetable Oils and Processed Foods Destroy Our Health — and How to Recover! by Chris A. Knobbe, MD, and Suzanne Alexander, M.Ed, provides an eye-opening look at how these oils undermine our health and offers a path toward recovery through ancestral eating.
Dark Calories: How Vegetable Oils Destroy Our Health and How We Can Get It Back
By Catherine Shanahan, MD
View on Amazon
The Ancestral Diet Revolution: How Vegetable Oils and Processed Foods Destroy Our Health — and How to Recover!
By Chris A. Knobbe, MD and Suzanne Alexander, M.Ed
View on AmazonFrequently Asked Questions
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Seed oils, often called “vegetable oils,” are industrially processed oils extracted from seeds like soybean, canola (rapeseed), corn, sunflower, safflower, cottonseed, grapeseed, and rice bran. They are a modern addition to the food supply and were virtually absent from the human diet before the early 1900s.
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Seed oils are high in unstable omega-6 fatty acids, which are easily oxidized during processing, storage, and cooking. This oxidation produces toxic byproducts—called lipid oxidation products (LOPs)—that can trigger inflammation and contribute to chronic diseases.
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No. Olive, avocado, and coconut oils are extracted from the fruit or pulp (not the seed) and are much less processed. These traditional oils are far more stable and have been used safely for centuries.
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Seed oils originally came from industrial byproducts, such as cottonseed oil used in soap making. In 1911, Procter & Gamble introduced hydrogenated cottonseed oil under the brand name Crisco, marketed as a “clean” alternative to lard and butter. Over the next century, seed oils replaced traditional animal fats in most American households.
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Research and historical patterns link seed oils to rising rates of obesity, diabetes, coronary artery disease, cancer, Alzheimer’s disease, autoimmune conditions, and other chronic illnesses.
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No. Historical food data shows Americans have eaten similar total amounts of fat since the 1900s—but the type of fat shifted drastically. Traditional animal fats and butter were replaced by industrial seed oils, correlating with the rapid rise of chronic diseases.
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Linoleic acid is the primary omega-6 fat in seed oils. While small amounts in whole foods like nuts and seeds are safe, the concentrated and oxidized linoleic acid from industrial oils is unstable and harmful when consumed in large amounts.
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No. Even before cooking, most seed oils have already gone through heavy industrial processing with heat, chemicals, and solvents. This exposes them to oxidation, meaning they can be harmful even when bottled and used “cold.”
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Yes, there are safer oil extraction methods, but the healthfulness of the oil depends not only on the extraction technique but also on how minimally the oil is processed:
Mechanical/Expeller Pressed Oils: These are extracted using heat and pressure. However, even “mechanical” or “expeller” pressing often involves heat, which can damage delicate fats and create toxic compounds known as lipid oxidation products (LOPs). These LOPs are a major reason why many seed oils are harmful, more so than their omega-6 content.
Cold Pressed Oils: Cold pressing minimizes heat exposure during extraction. However, simply being “cold pressed” does not automatically mean the oil is unrefined. Many cold pressed oils are still refined afterward, removing natural antioxidants and making them more prone to LOP formation.
Virgin/Unrefined Oils: Oils labeled “virgin” or “unrefined,” such as traditional sesame or olive oils, are made using gentle processes and avoid the damaging high heat and harsh chemical refining steps. These retain beneficial antioxidants and typically have fewer harmful compounds, making them safer choices.
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Stable, traditional fats include:
Olive oil (extra virgin, cold-pressed)
Avocado oil
Coconut oil
Butter and ghee
Beef tallow, pork lard, and duck fat (from pasture-raised, grass-fed sources)
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Always check product labels for the “Hateful Eight” oils (soybean, canola, corn, sunflower, safflower, cottonseed, grapeseed, rice bran).
Cook at home using healthy oils.
Choose snacks and packaged foods made without seed oils (use resources like SeedOilFreeSnacks.com).
Ask restaurants what oils they use before ordering fried foods.
Acknowledgements
This article is made possible through the dedicated work of countless doctors, scientists, and researchers who have shed light on the dangers of industrial seed oils. Special recognition is given to Dr. Catherine Shanahan, MD and Dr. Chris A. Knobbe, MD—along with Suzanne Alexander, M.Ed—whose tireless efforts in research, education, and advocacy have been instrumental in unveiling the hidden truth about these oils.
Written by: Jason Merrill, Publish date: Aug 20, 2025
Sources:
Carson SA. Racial differences in body mass indices of men imprisoned in 19th Century Texas. Economics & Human Biology. 2009;7(1):121-27
Carson SA. Black and White Body Mass Index Values In Developing Nineteenth Century Nebraska. Journ Biosocial Sci. 2015;47(1):105-119
Ward ZJ, Bleich SN, Cradock AL, et al. Projected U.S. State of Level Prevalence of Adult Obesity and Severe Obesity. N Engl J Med. 2019;381:2440-2450
Herrick JB. Clinical Features of Sudden Obstructions of the Coronary Arteries. JAMA. 1912;LIX(23):2015-2022. Doi:10.10001/jama.1912.04270120001001
Jones DS Podolsky SH, Green JA. The Burden of Disease and the Changing Task of Medicine. N Engl J Med. 2012; 366:2333-2338. DLI: 10.1056NEJMp1113569
Ahmed AM. History of Diabetes Mellitus. Saudi Med J. 2002;23(4):373-378;
Centers for Disease Control (CDC): https://www.cdc.gov/diabetes/communication-resources/diabetes-statistics.html
Waldman M, Lamb M. Dying For A Hamburger. New York, Thomas Dunne Books, 2005
Dementia, 2 Sep 2021. World Health Organization (WHO): https://www.who.int/news-room/fact-sheets/detail/dementia
Hitzenberger K, Richter-Quittner M. Ein Beitrag zum Stoffwechsel bei der vasculären Hypertonie. Weiner Arch Innere Med. 1921;2:189-216
Kylin E. Hypertonie and zuckerkrankheit. Zentralblatt für Innere Medizin. 1921;42:873-877
https://www.hhs.gov/press-room/revising-gras-pathway.html
https://www.food-safety.com/articles/10208-rfk-jr-directs-fda-to-explore-ways-to-eliminate-gras-rule-for-food-ingredients
Olver, Lynne. The Food Timeline, Dec 2021: https:///thefoodtimeline.org
