The Dark History of Canola Oil: Is This “Heart‑Healthy” Fat Actually Healthy?
CANOLA OIL — OXIDATION, LDL, & HEART DISEASE
The Dark History of Canola Oil: Is This “Heart-Healthy” Fat Actually Healthy?
Canola oil is widely promoted as a heart-healthy fat — but its origins as an industrial lubricant, extreme processing, and effects on oxidation raise serious questions. In this long-form, science-based breakdown, we examine how canola oil is made, why it lowers LDL, what early research actually found, and whether focusing on cholesterol alone misses the real drivers of cardiovascular and metabolic disease.
Author
Craig McCloskey
Board-Certified Nutritionist
Canola oil is one of the most widely consumed fats in the modern food supply. It’s found in restaurant fryers, packaged snacks, salad dressings, infant formulas, and even products marketed as heart healthy. Yet despite its wholesome branding, canola oil is a remarkably new invention—barely half a century old—and its origins raise important questions about whether it truly deserves a place in a human diet.
This article takes a science‑based look at where canola oil came from, how it’s made, why it earned its health halo, and what modern research suggests about its long‑term effects on human health.
A Food That Didn’t Exist for Most of Human History
For nearly all of human evolution, dietary fats came from animals, fruits, nuts, and seeds that could be eaten in their natural state. Olive oil, for example, is simply pressed from olives—no complex chemistry required. Butter comes from cream. Tallow comes from rendered beef fat.
Canola oil is fundamentally different.
Although the rapeseed plant itself has been cultivated for thousands of years, its oil was never traditionally consumed as food. Historical records suggest rapeseed oil was primarily used for lamps as early as the 13th century, not for cooking or nutrition. Its chemical composition made it poorly suited for human consumption, largely due to its high concentration of erucic acid—a fatty acid later shown to be toxic in even relatively small, chronic doses.
The modern story of canola oil doesn’t begin in kitchens. It begins in engines.
Read the full transcript
Canola oil just celebrated its 50th birthday this past year, which is pretty strange to say about a food. When we have people on this planet who are older than canola oil, that alone should raise some red flags. As you’re going to learn today, canola oil wasn’t invented as food at all — it was originally developed as an engine lubricant. Canola oil was first produced in 1974, but its story begins much earlier with the rapeseed plant. Rapeseed dates back thousands of years and was cultivated in India, but it was never traditionally eaten. The first recorded use of rapeseed oil in the 13th century was for lamps, not for food. Fast forward to the 1940s. In 1945, the first industrial rapeseed processing plants were built so the oil could be used to lubricate ship engines during World War II. The United States couldn’t grow enough rapeseed domestically, so Canada was asked to grow large quantities for engine lubrication. When the war ended and steam engines were replaced by diesel engines, the demand for rapeseed oil collapsed. However, Canada was still growing roughly 143,000 acres of rapeseed and needed a way to monetize the crop. Over the next several decades, researchers worked to convert this industrial oil into something that could be eaten. The problem was toxicity. Rapeseed oil is naturally high in erucic acid, which is toxic even in small amounts. Chronic exposure to erucic acid has been linked to myocardial lipidosis — a condition where fat accumulates around the heart and impairs function. Through genetic manipulation, selective breeding, and seed splitting, scientists eventually created a new version of rapeseed that was low in erucic acid and higher in oleic acid, a monounsaturated fat also found in olive oil. This new crop was named canola — short for Canadian Oil, Low Acid. In 1978, the name canola oil was trademarked. Despite initial resistance, it was eventually granted GRAS (Generally Recognized as Safe) status, allowing it to enter the food supply without limits. By the 1990s, canola oil was widely used worldwide. Today, Canada grows over 22 million acres of genetically modified canola, most of it heavily treated with pesticides. Canola oil is one of the most ultra-processed foods in the modern diet. Extracting oil from canola seeds requires more than 40 industrial steps. The seeds are crushed, pressed, chemically washed with solvents like hexane, then bleached and deodorized to remove rancid odors. By the time canola oil reaches store shelves, it has already undergone significant oxidation. It is typically bottled in clear plastic, exposed to light, air, and heat — all of which further accelerate oxidation. Although canola oil may lower LDL cholesterol, lowering LDL alone does not prevent heart disease. In fact, oxidation of LDL is a key driver of cardiovascular disease. Consuming oxidized oils increases oxidative stress in the body and depletes antioxidant nutrients like vitamin E and vitamin C. Early studies conducted between 1978 and 2000 consistently found that canola oil consumption led to heart problems, vitamin E deficiency, rigid cell membranes, impaired growth, and increased mortality. Interestingly, these effects were significantly reduced when stable saturated fats like butter, tallow, ghee, or cocoa butter were added to the diet. Despite this early evidence, canola oil received a heart-healthy endorsement in 2006 based largely on its LDL-lowering effect. However, large studies show that approximately 75% of people hospitalized for heart attacks have normal or low LDL levels. The real issue isn’t LDL itself — it’s oxidized LDL. Seed oils like canola oil are highly susceptible to oxidation during processing, storage, cooking, and digestion. Canola oil is also high in linoleic acid. While linoleic acid is essential in small amounts, excess intake leads to accumulation in body fat and breakdown into oxidized linoleic acid metabolites (OXLAMs), which are linked to obesity, cardiovascular disease, neurological disorders, and metabolic dysfunction. Observational studies often suggest benefits from canola oil, but these studies are heavily influenced by healthy user bias. People who consume canola oil often engage in other health-promoting behaviors that skew results. The takeaway is not fear — it’s awareness. Canola oil is a highly engineered, oxidatively unstable product with no meaningful evolutionary precedent in the human diet. Is it really food — or should it have stayed an engine lubricant? Thanks for being here. I’ll talk to you next time.
From Industrial Lubricant to Grocery Store Staple
During World War II, rapeseed oil found a new role as an industrial lubricant. Its unique fatty acid profile made it particularly useful for lubricating steam engines and ship machinery. As global demand surged, Canada became one of the primary producers of rapeseed to support the Allied war effort.
When the war ended, the industrial demand for rapeseed oil collapsed. Steam engines were phased out, diesel technology advanced, and Canada was left with vast acreage devoted to a crop that no longer had a clear purpose.
Rather than abandoning rapeseed cultivation, Canadian researchers spent the next several decades attempting to transform this industrial oil into something that could be sold as food. The major obstacle was erucic acid, which had been linked to myocardial lipidosis—a condition characterized by abnormal fat accumulation in heart tissue.
Through genetic manipulation, selective breeding, and seed splitting, scientists eventually produced a novel version of rapeseed that was significantly lower in erucic acid. This new crop was officially introduced in the 1970s and renamed canola—short for Canadian Oil, Low Acid.
In 1974, canola oil entered the food supply.
Canola oil is a modern invention with no meaningful evolutionary precedent. For most of human history, dietary fats came from stable animal fats and minimally processed plant sources.
How Canola Oil Is Actually Made
Unlike naturally oily foods, canola seeds contain relatively little extractable fat. Producing canola oil on an industrial scale requires extensive processing—often involving more than 40 distinct steps.
After harvesting, seeds are cleaned, crushed into flakes, and subjected to high‑pressure mechanical pressing. Even then, a large portion of the oil remains trapped in what’s known as “canola cake.” To extract the rest, manufacturers rely on chemical solvents—most commonly hexane.
At this stage, the oil is not remotely edible. It smells rancid, contains oxidation byproducts, and bears little resemblance to food. To make it marketable, the oil undergoes multiple rounds of refining, bleaching, and deodorizing, often at high temperatures.
By the time canola oil reaches store shelves, it has been chemically altered, deodorized, and stripped of many naturally occurring protective compounds. It is typically packaged in clear plastic bottles, where exposure to light, heat, and oxygen continues to degrade the oil over time.
From a biochemical perspective, canola oil is one of the most ultra‑processed substances commonly consumed by humans.
Oxidation: The Central Problem With Canola Oil
Canola oil is often praised for its fat profile—low in saturated fat and relatively high in monounsaturated fat. But this framing overlooks a crucial issue: oxidation.
Polyunsaturated fats and even monounsaturated fats are inherently unstable. When exposed to heat, light, or oxygen, they readily oxidize, forming reactive byproducts that damage cells, proteins, and DNA. This oxidation begins during industrial processing and continues during storage, cooking, and digestion.
While canola oil has been shown to lower LDL cholesterol, lowering LDL alone does not equate to better cardiovascular health.
In other words, an oil that lowers LDL while simultaneously increasing oxidative stress may offer little real‑world benefit—and may even increase risk.
Lowering LDL cholesterol alone does not prevent heart disease. What matters more is whether LDL particles become oxidized — a process driven by oxidative stress, unstable fats, and ultra-processed oils.
What Early Research Actually Found
Before canola oil earned its reputation as a heart‑healthy staple, early animal and mechanistic studies raised serious concerns.
Research conducted between the late 1970s and early 2000s consistently found that diets high in canola oil were associated with:
Structural changes to heart tissue
Reduced red blood cell count and size
Vitamin E depletion
Increased oxidative damage
Rigid cell membranes
Impaired growth and development
Notably, these negative effects were significantly reduced when stable saturated fats—such as butter, tallow, cocoa butter, or ghee—were added to the diet. This suggests that fat stability, rather than saturated fat content alone, plays a critical role in metabolic health.
Vitamin E depletion is particularly concerning. Vitamin E acts as a major antioxidant that protects fats within cell membranes from oxidative damage. Diets high in oxidized oils increase the body’s requirement for antioxidant nutrients while simultaneously depleting them.
The Heart‑Healthy Label: Marketing vs. Mechanism
In 2006, canola oil received a heart‑healthy endorsement based largely on its ability to lower LDL cholesterol. This decision reflected a long‑standing cholesterol‑centric model of heart disease—one that modern research increasingly questions.
Oxidative stress, chronic inflammation, metabolic dysfunction, and nutrient depletion are far more predictive of long‑term disease risk than LDL alone. Canola oil may improve cholesterol markers on paper while simultaneously contributing to these deeper issues.
Linoleic Acid and Long‑Term Accumulation
Another underappreciated issue with canola oil is its linoleic acid content. Linoleic acid is an essential omega‑6 fatty acid, but only in small amounts. Modern diets supply linoleic acid in quantities far beyond historical norms.
Unlike saturated fats, linoleic acid is poorly cleared from tissues and can remain in the body for years, compounding oxidative stress over time.
Observational Studies and the Healthy User Bias
Many studies supporting canola oil rely on observational data. These studies can identify correlations, but they cannot establish causation.
People who consume more canola oil often engage in other health‑promoting behaviors: eating more whole foods, exercising regularly, managing stress, and avoiding smoking. Meanwhile, higher saturated fat intake is often associated with fast food consumption, smoking, alcohol use, and sedentary lifestyles.
This “healthy user bias” makes it difficult to isolate the effects of canola oil itself. Without controlled trials that account for oxidation, nutrient status, and fat stability, conclusions remain limited.
Observational studies linking canola oil to better health outcomes cannot establish causation. Health-conscious behaviors often cluster together, making it difficult to isolate the effects of the oil itself.
A More Ancestral Perspective on Dietary Fat
For most of human history, dietary fats were stable, minimally processed, and consumed close to their natural state. Butter, tallow, olive oil, coconut oil, and animal fats supported human populations for generations without modern epidemics of metabolic disease.
In contrast, canola oil is a novel, heavily engineered product with no meaningful evolutionary precedent. Its rapid rise parallels the increase in ultra‑processed foods and chronic disease.
If you’re looking to reduce oxidative stress and support long‑term health, prioritizing stable fats—especially for cooking—may be a more biologically appropriate strategy.
Practical Takeaway
Canola oil is not inherently toxic in acute doses, but its origins, processing methods, oxidative instability, and biochemical effects raise legitimate concerns about long‑term consumption.
Lowering LDL cholesterol alone is not enough to define health. The quality, stability, and processing of dietary fats matter—perhaps more than we were ever taught.
As with most nutrition debates, context matters. But when a product begins as an engine lubricant and requires extensive chemical manipulation to become edible, it’s worth asking whether it truly belongs on our plates.
