Canola oil was considered a healthy cooking oil for years, thanks to its low saturated fat content.
When the low-fat craze came to an end — and research debunked the myth that saturated fats were to blame for cardiovascular disease — canola oil became a subject of controversy.
In just a quick search, you can find experts who swear by it and others warning against it, so what’s the truth?
When you take a closer look, canola oil isn’t everything it was once cracked up to be. In fact, consuming it could increase inflammation and affect your gut health, among other side effects. Read on to find out exactly why you might want to ditch this “heart-healthy” oil for good.
Unlike olive oil, coconut oil, or avocado oil, which come from the foods they’re named after, canola oil has a more complicated origin.
The canola seed comes from a modified rapeseed plant (Brassica napus), but there are other varieties of the Brassica family (B. rapa and B. juncea). These special seeds were achieved through cross-breeding in the 1960s in an effort to make rapeseed oil safer for human consumption.
The result was the genetically modified canola plant. Companies claim it’s a non-GMO product, even though it comes from a genetically modified plant[*].
However, 80% of canola plants grown in Canada (the number one producer of canola) are genetically modified to withstand the treatment of herbicides (like glyphosate, aka Round-Up, a Monsanto herbicide).
Originally, raw rapeseed oil was extremely high in erucic acid, which is potentially toxic and can damage the heart, liver, and kidneys[*]. To stay in business, Canadian rapeseed oil manufacturers looked for a way to reduce this component through cross-breeding, and the canola crop was born. “Canola” is a combination of “Canadian” and “ola” (oil), named after its place of origin.
The Canola Council of Canada defines canola oil seeds as those from the Brassica family that contain less than 2% erucic acid and less than 30 micromoles of glucosinolates.
How It Got On Store Shelves
In 1956, the FDA banned rapeseed oil because of high amounts of erucic acid (30-60%), which made it unfit for human consumption. Simultaneously, the high levels of glucosinolates in rapeseed meal made it unfit for animal consumption[*].
This prompted rapeseed oil manufacturers to hire researchers from Saskatoon and the Universities of Alberta and Manitoba to develop a new rapeseed variety with low doses of these components.
By 1974, they succeeded in creating the first variety with low erucic acid and low glucosinolates. They called it low-erucic acid rapeseed (LEAR).
In 1978, the Western Canadian Oilseed Crushers Association used the name “canola” to trademark these rapeseed varieties, but by 1980, the Canola Council of Canada took over the trademark.
In 1985, the FDA declared canola oil as GRAS (generally recognized as safe) and it was finally introduced to the American market. It began appearing on food labels by 1988[*].
Modern Canola Oil
Even though canola started out with less than 2% erucic acid, by 1990 the levels dropped to 0.5-1%. It also stopped being a trademark and became a generic name for any rapeseed oils that complied with Canola Council of Canada standards.
Thanks in part to this modification, the global consumption of this oil rose by 1175% between 1961 and 1991. It is now the third most-produced oil in the world, following palm oil and soybean oil, and Canada is the biggest producer[*]:
- Canada: 15.6%
- China: 14.8%
- India: 7.9%
This high demand and production allowed it to sneak into kitchens and processed foods without resistance.
Flawed research (and the news that covered this research) led people to believe that this oil was healthy, which reinforced its consumption.
Per serving (one tablespoon), canola oil contains[*]:
- 124 calories (all from fat)
- 9 grams of monounsaturated fat
- 4 grams of polyunsaturated fat
- 1279 milligrams of omega-3
- 2610 milligrams of omega-6
- 1 gram of saturated fat
The total fatty acids in oil from canola have a 2:1 ratio between omega-6s and omega-3s, which isn’t ideal. The typical Western diet already contained too much omega-6 before this change, and when your omega-6 levels are higher than your omega-3 levels, it’s a recipe for inflammation.
The high amount of monounsaturated fat and low amount of saturated fat is the reason most nutrition professionals considered it an excellent cooking oil. However, this ratio of fats makes canola extremely unstable, which means they’re easily oxidized high heat — and that negatively affects your health.
This oil is highly processed and requires synthetic antioxidants to prevent it from going rancid too quickly. This refining method makes canola unhealthy for you in multiple ways. Here’s a breakdown of the process.
Step #1: Pre-Extraction Prepping
The seeds are ground and sieved to remove the husks and foreign matter away from the softer, oily part of the seed.
Step #2: Extraction With Solvents
The most common extraction method uses a solvent called hexane. The seeds are added to a machine along with the solvent (either hexane or a combination of chloroform and methanol), and it goes through a process of boiling, rinsing, and extracting.
This method removes most polyphenols (healthy phytonutrient compounds). One study comparing different types of oil extractions found that commercial solvent-extracted canola oil had virtually no polyphenols left[*]. So it’s in step 2 when many of the potentially healthy components of the oil are removed and neutralized.
Step #3: Semi-Refining
The oil is degummed (removing lipids), neutralized, bleached, and winterized (removing waxes).
Step #4: Deodorizing
Step #5: Adding Antioxidants
Canola oxidizes easily. Oxidation is another term for “going bad.” The monounsaturated fats make it unstable and more prone to oxidation. This means that the oil is more sensitive to light, oxygen, and high temperatures than saturated oils.
That’s why it’s necessary to add synthetic antioxidants that increase shelf life, such as TBHQ, BHA, and BHT, all of which are potentially dangerous. Without this step, canola oil would quickly turn rancid when cooked over high heat.
Thanks to these antioxidants, it also acquires a high smoking point of 400°F (204°C)[*].
In comparison, coconut and MCT oil don’t need artificial antioxidants because the saturated fats give them a naturally long shelf life and a high smoke point. Their smoke points are 350°F and 320°F, respectively.
Despite what marketing messaging tells you, canola oil is bad news. Here are 10 reasons to stay away from it.
#1: Contains Trans Fats (Even If the Label Says Otherwise)
Take those “0% trans fats” labels plastered over canola oil bottles with a grain of salt.
The FDA allows companies to claim there are no trans fats in their oil as long as the trans fat content stays below 0.5 gram per serving. According to the FDA: “If a serving contains less than 0.5 gram, the content, when declared, must be expressed as 0 g”[*].
One study published in the Journal of Agricultural and Food Chemistry found that refined canola oil contains around 0.6% of trans fatty acids[*]. This amount may not sound like a lot until you realize the daily recommended intake of trans fat is zero.
You’re not supposed to consume any trans fats because they actively harm your health. Nevermind the fact that most people don’t measure out their cooking oil, leaving the total daily trans fat consumption potentially a lot higher than the label says.
The World Health Organization (WHO) recommends keeping trans fat at less than 1% of your total daily calorie intake[*]. This means that with each serving of oil (one tablespoon, 0.6% of trans fat) you’d be hitting the limit set by the WHO (>1% of trans fat). Consider that this oil is used in a number of processed foods, many of which Americans consume every day.
- Decrease HDL (good) cholesterol
- Increase inflammation
- Cause endothelial dysfunction (bad functioning of the lining of your blood vessels)
- Lower insulin sensitivity
- Increase the risk of coronary heart disease and strokes
- Induce body fat accumulation
One meta-analysis found that replacing just 2% of energy from carbs, saturated fat, monounsaturated fat, or polyunsaturated fat with 2% of energy from trans fat increased the risk of heart attack or heart disease death by 24%, 20%, 27%, and 32% respectively[*].
In other words, you’re better off eating avocado oil (monounsaturated fat), walnut oil (polyunsaturated fat), or coconut oil (saturated fat) than canola oil.
#2: Synthetic Antioxidants Are Harmful
In their natural form, vegetable oils lack oxidative stability, so they’ll quickly turn rancid if left untreated. Manufacturers found a way around this by adding synthetic antioxidants, most commonly TBHQ, BHA, and BHT.
These added antioxidants are often used in packaged foods to preserve freshness and control the texture of foods, including potato chips, cookies, and cereals. For example, without TBHQ, chips would become soft and lose their crunchiness.
When consumed in large doses for long periods of time, these preservatives have carcinogenic and toxic effects, as evidenced by experiments that showed:
- BHA caused tumors in animal stomachs[*]
- BHT induced liver tumors in animal models[*]
- TBHQ caused liver enlargement and neurotoxicity, including convulsions and medullary paralysis in vitro and in animal models[*]
The FDA said these antioxidants are not toxic in small doses, but there’s one caveat: people tend to eat more than the acceptable limit of these preservatives. No one eats one serving of chips, right? That’s where the potential danger lies.
The World Health Organization set the following acceptable daily intakes (ADI):
The International Programme On Chemical Safety (IPCS) by the WHO evaluated the real intake of these three antioxidants in different populations around the world. It found that most people are really close to the limit, while high consumers of fat often surpass the ADI[*][*][*].
Here are just a few of their findings:
- High consumers of fat ate up to 180%, 300%, 680%, and 700% of TBHQ ADI, depending on the country.
- In the U.S., the mean consumption of TBHQ was 90% of ADI.
- High consumers of fat ate up to 1600%, 1800%, and 2000% of BHT ADI, depending on the country.
- In the U.S., the mean consumption of BHT was 130% of ADI.
- High consumers of fat ate up to 380%, 950%, 1200%, and 1400% of BHA ADI, depending on the country.
- In the U.S., the mean consumption of BHA was 190% of ADI.
This shows that even though the preservatives in canola oil alone are not enough to cause adverse effects, they contribute to your daily consumption of synthetic antioxidants. This can easily surpass the acceptable limits because they’re present in many processed foods — and this can cause harmful effects.
#3: Contains a High Ratio of Omega-6 to Omega-3 Fatty Acids
Canola oil is rich in polyunsaturated fatty acids (PUFAS), which are necessary for optimal health. However, not all PUFAs are created equal. The ratio of omega-3 to omega-6 in foods matters because each has different effects on your body.
Omega-3 fatty acids are anti-inflammatory and contribute to the prevention of disease, while omega-6 fatty acids induce inflammation in your body[*].
Canola oil has a 2:1 omega-6 to omega-3 ratio, which isn’t so uneven in itself, but it negatively contributes to the already disproportionate ratio in the Western diet. While your ancestors ate an omega 6-3 ratio of 1:1, people eating a Standard American Diet consume these fats in a ratio of 20:1[*].
This increase in omega-6 causes chronic inflammation, which triggers disorders like atherosclerosis, nonalcoholic fatty liver disease (NAFLD), cardiovascular disease, obesity, diabetes, inflammatory bowel disease, rheumatoid arthritis, and Alzheimer’s. One review concludes that a disproportionate intake of omega-6 over omega-3 is highly prothrombotic, proinflammatory, and proaggregatory[*].
If you want to balance your ratio, skip canola in your salad dressings and go for better sources of omega-3s, such as walnut oil or flax oil.
#4: Reduces Antioxidant Protection
One of the biggest downsides of canola is it reduces your body’s antioxidant capability.
- Superoxide dismutase (SOD): This antioxidant prevents the formation of free radicals by neutralizing harmful oxygen molecules.
- Glutathione peroxidase: It neutralizes peroxide compounds that cause damage.
- Catalase: This enzyme converts hydrogen peroxide molecules to harmless oxygen and water.
Without these defenders, your cells are extremely vulnerable to inflammation, early aging, and multiple diseases.
One of the consequences of lower antioxidants is lipid peroxidation — the oxidation of fatty deposits. When a free radical attacks fat in your body, more free radicals called lipid radicals are created, and they continue to cause damage in a chain reaction.
#5: Spikes Inflammation
A direct effect of lower antioxidant ability, excess omega-6s, and trans fat consumption is chronic inflammation, which is at the center of many disorders, like[*]:
- Rheumatoid arthritis
- Multiple sclerosis
Keeping inflammation down is key to preventing and managing disease, and canola doesn’t help with that.
One study found that consumption of partially-hydrogenated vegetable oils (like canola) drastically increased inflammatory biomarkers, the indicators of the level of inflammation in your body[*].
Another study discovered that inflammation stayed the same when patients ate either a traditional Western diet or canola oil, suggesting canola is not more protective than junk food[*].
#6: Impairs Cognitive Function
One recent study published in Nature found adding canola oil to a regular diet for six months caused[*]:
- Impairment in working memory.
- Weaker synaptic integrity — synapses are the basic biological connections that allow neurons to communicate with each other and other non-neuronal cells
- An increase in the ratio of insoluble Aβ 42/40, amino acids that deposit in the brain and play a role in Alzheimer’s disease.
By reducing the strength of synapses, canola oil may put you at risk of neurodegenerative disorders and nervous system dysfunction, because synaptic integrity is necessary for neurotransmission.
Research overwhelmingly agrees that the main characteristic of Alzheimer’s disease is a loss of synaptic connectivity and density in the neocortex and hippocampus[*].
#7: Hinders Longevity
In the most recent study, subjects on a diet containing 10% canola oil died 13% faster than those on a soybean oil-supplemented diet[*]. The animals died 40% faster when compared to those on a diet supplemented with omega-3[*].
According to the researchers, the most likely causes for this shorter lifespan are:
- Lower antioxidant status.
- Phytosterol content. Phytosterols are usually considered “healthy,” but in excess they increase the risk of heart disease[*][*]. Canola oil is rich in a type of phytosterol called campesterol, which was found in high amounts in the organs of animals who died faster[*].
Human trials are still needed to evaluate how accurately these effects translate, but these preliminary findings should be enough to make you rethink your stance on canola.
#8: Triggers Insulin Resistance
Canola oil messes with an important marker of health: insulin sensitivity.
Insulin sensitivity measures how well your body can handle increases in your blood sugar. If you’re insulin sensitive, it means you only need a small amount of insulin to take care of glucose spikes after you eat. That’s the way it should be.
When you lose insulin sensitivity thanks to bad dietary habits, you become insulin resistant. Your body has to produce large amounts of insulin to take care of blood sugar. Insulin resistance is a precursor to diabetes.
One study observing the anti-diabetic effects of vegetable oils found that canola contributed to type 2 diabetes onset by increasing insulin resistance. In just four weeks, the group who ate canola oil developed the highest insulin levels[*].
Another study found that adding canola to a high-fat diet increased insulin resistance index by 78%[*].
#9: Damages Blood Vessel Function
Canola oil also has negative effects on your endothelium, the interior lining of your blood and lymphatic vessels. Endothelial cells cover your whole circulatory system. They are responsible for allowing white blood cells and hormones into the blood, filtrating nutrients, dilating and constricting blood vessels, and clotting blood.
One study found that consuming this oil for 10 weeks triggered endothelial dysfunction. This happened with pure canola oil, oil fried once, and oil fried 10 times[*].
Another paper found that when the oil was combined with salt (for example, in fried foods), blood vessels had more trouble contracting properly, which is a sign of endothelial dysfunction[*].
A dysfunctional endothelium is a root cause of cardiovascular disease like thrombosis, atherosclerosis, hypertension, hypercholesterolemia, and stroke[*]. It also provokes other non-cardiovascular diseases like diabetes, insulin resistance, kidney failure, and tumor growth.
#10: Worsens Hypertension
If you have high blood pressure, canola can make things worse.
One study found that in hypertensive subjects, blood pressure increased after just four weeks of consuming canola oil[*]. Another experiment got the same results, showing that canola consumption increased blood pressure after barely five weeks, when the study was supposed to last 13 weeks[*].
These effects in blood pressure are partly fueled by endothelial dysfunction and a lack of antioxidants.
Despite all this, canola is still considered a healthy cooking oil today. Some “experts” even suggest using canola instead of extra virgin olive oil due to the alleged heart health benefits, but there’s no evidence canola and olive oil are equal, and researchers advise against using them interchangeably[*].
Canola is one of the most controversial oils because there are staggering amounts of contradicting information about it.
Here are all the wrong reasons why canola is considered healthy (and why you shouldn’t fall for them).
Reason #1: The “Saturated Fat Is Bad” Myth
In the 1980s, the USDA published nutritional guidelines that favored carb consumption and demonized healthy fats — particularly saturated fats — because flawed research had found a link between dietary fat and lipid increases.
This fatphobia made experts recommend alternative cooking oils that were low in saturated fat, such as canola and other hydrogenated vegetable oils.
However, the myth that saturated fat is harmful has been widely debunked by newer and stricter research that confirms there’s no evidence that saturated fats increase the risk of heart disease or stroke[*][*].
Unfortunately, it’s taking a while for mainstream nutrition guidelines to catch up with this new information, so a diet low in saturated fat but high in mono- and polyunsaturated fat, popularized by the Mediterranean diet, is still heavily recommended. Ironically, the omega-6 polyunsaturated fats abundant in canola do increase the risk of heart disease and thrombosis by inducing clogged arteries[*].
Reason #2: Research Funded by Big Canola
The fat phobia that began 40 years ago significantly benefited manufacturers of sugar, grains, and vegetable oils. Canola is now among the top five oilseed crops cultivated worldwide.
The spike in canola sales after scientists made it safe brought in exorbitant funds for oilseed corporations, which they now use to fund research on canola. In fact, the most prominent research on the positive health benefits of canola oil are funded by these corporations:
- Canola Council of Canada
- U.S. Canola Association
This creates an obvious conflict of interest since both of these organizations are for-profit and clearly biased.
In their mission statement, the Canola Council of Canada states that “our goal is to ensure the industry’s continued growth, demand, stability, and success.” According to their website, the U.S. Canola Association “works to support and advance U.S. canola production, marketing, processing and use through government and industry relations” [*][*].
It’s no surprise that all the research they’ve funded favors canola oil. Just take a look:
- A 2013 review titled “Evidence of Health Benefits of Canola Oil” was funded by both the Canola Council of Canada and U.S. Canola Association, and done by employees of both organizations.
- A 2016 study that found the oil reduced abdominal fat in obese individuals was supported by Agriculture and Agri-Food Canada, Canola Council of Canada, Dow Agrosciences and Flax Council of Canada[*].
- One 2011 study that concluded it’s safe to replace dairy fat with canola oil received funding from Pulse Canada, the Saskatchewan Pulse Growers, the Canola Council of Canada, Unilever, and other corporations[*].
For comparison, none of the studies showing negative side effects of canola (used in this article) received funding from corporations. But the bias doesn’t end there. The Canola Council of Canada has also granted funds for studies that demonize saturated fats.
For example, a 2017 review published by the AHA titled “Dietary Fats and Cardiovascular Disease: A Presidential Advisory From the American Heart Association” advises against coconut oil consumption because it’s high in saturated fat and recommends polyunsaturated fats instead. Another study that recommended lowering saturated fats in favor of carbs received partial support from the Canola Council of Canada[*].
These biased studies fuel confusion when media outlets pick them up and share their manipulated results with the public.
Reason #3: The Health Benefits Are Exaggerated
Canola oil is not as heart-healthy as it once promised. That being said, there have been a few human studies (not funded by canola corporations) that show minor positive effects on lipids. In a four-month trial, LDL went down, while there was no effect on HDL or total cholesterol[*].
Even though the effects weren’t drastic, research like this may have been blown out of proportion. Because canola contains a type of omega-3 called ALA (alpha-linolenic acid), some positive effects are to be expected, but they aren’t significant enough to make sweeping health claims about canola oil while ignoring the negative aspects.
Studies about canola and heart health have shown mixed results. For example, in one randomized clinical trial in patients with a prior heart attack, supplementing with 2 grams of ALA per day for 40 months had no effect on cardiovascular health[*].
Cut Canola Oil Out of Your Diet
Canola is a modified oilseed created by scientists to be less toxic than the original rapeseed oil. Extracting canola oil requires solvents (which create trans fats) and synthetic antioxidants to keep it stable. This is in stark contrast to other oils that don’t need to be refined, like walnut or coconut oil.
Outdated views about saturated fat and research funded by canola associations contributed to the rise of this oil as a healthy alternative, but newer research says you should avoid it.
Impartial studies show that consuming canola oil comes with side effects, including lower antioxidant ability, higher inflammation, higher risk of heart disease, insulin resistance, and hypertension, despite biased studies that want to put canola under a better light.
The bottom line is there are healthier cooking oils that don’t come with these risks and still retain a naturally high smoke point, such as avocado oil, coconut oil, and ghee. Use these for high heat cooking and sautéing as your healthiest options. Opt for extra virgin olive oil or flax oil (or a combination) for salad dressings, and enjoy your healthy oils without worrying about your cholesterol levels.
Vegetable oils, in general, are detrimental to your health and canola is no exception.