If you stray into the more health and wellness-focused parts of the internet, it won’t be too long before you find someone deriding the so-called evils of seed oils. One that seems to bear the brunt of a lot of this ill-feeling is canola oil – but is it really all bad? It’s time we took a good look at some of the science behind seed oils, and maybe bust a couple of myths along the way.

What is canola oil?

Canola oil is the name used in some countries, notably the US and Canada, for the food-grade version of rapeseed oil. In other countries, such as the UK, you can find bottles labeled “rapeseed oil” on the supermarket shelves next to all the other cooking oils. Other, less refined versions of the oil have industrial uses, such as lubricating heavy machinery.

Whatever you call it, the oil is derived from the seeds of the rapeseed plant. Unfortunately, the terminological confusion doesn’t stop here, as the plant is often known by the confoundingly similar name of oilseed rape. It's a member of the mustard family (Brassicaceae), and in places where it’s cultivated you will see fields carpeted in bright yellow flowers throughout spring and summer.

Canola oil is one of the top edible oils consumed in the US. It’s very versatile, and can be eaten cold as a dressing or dip – like olive oil – or used for frying, baking, and roasting. 

That sounds pretty perfect, right? An oil that can do all that, plus provides an alternative for those who are allergic to other common oils, like soybean or peanut, surely can’t be all bad. So why have some people seemingly turned against it?

Why do some people claim canola oil should be avoided?

The controversy over canola oil has been raging for a good few years now, but in the age of TikTok it’s getting more and more difficult to avoid hearing a cacophony of opinions on all sorts of nutrition topics. Unfortunately, amid all this noise, it can be hard to pick out fact from fiction.

One of the major claims about canola oil centers around how it is processed. Unless you’re specifically buying “cold-pressed” oil, which is more expensive and can be hard to get hold of, getting the oil out of the seed in the first place requires the application of heat, as well as treatment with a solvent. Some have claimed that the solvent, generally hexane, can pose a risk to humans, and that the heat can alter the composition of the oil to make it less healthy.

The Harvard T.H. Chan School of Public Health previously put some of these claims to Adjunct Associate Professor of Nutrition Dr Guy Crosby.

First, on the topic of hexane solvent, Dr Crosby pointed out that this method of extracting oils has been used for decades with no evidence of adverse effects, and only very tiny amounts of hexane are left behind after the extraction process. Dr Crosby concluded, “There appears to be very little reason for concern about the trace levels of hexane in canola oil.”

As to the claims about the composition of the oil itself, canola oil actually stacks up as pretty average compared to lots of other commonly used oils. 

One big concern for many people is the level of trans fats it contains. These types of unsaturated fats have been linked to an increased risk of heart disease and stroke, due to their effects on the balance of “good” and “bad” cholesterol within the body, to the point where some jurisdictions have banned the use of artificial versions in food products. 

Canola oil does contain very low levels of trans fats, but according to Dr Crosby these levels are not too dissimilar to those found in soybean or walnut oil.

However, claims that canola oil is somehow “toxic” are still rife on social media. Some of this stems from a misunderstanding about the different types of rapeseed oil, which we mentioned earlier. Whilst you definitely would not want to eat the industrial version of the stuff, canola oil that has been produced for consumption has been made to contain much lower levels of a chemical called erucic acid, which was previously linked to cardiotoxicity in rats. While more recent research has begun to challenge some of these earlier claims, the fact is that the amounts of erucic acid remaining in canola oil are considered safe. 

There was also a curious case in the early 1980s of a disease that was eventually labeled Toxic Oil Syndrome. Affecting thousands of people in 14 regions of Spain, the disease tragically caused many deaths and left many more survivors with long-term complications. It was blamed on contaminated rapeseed oil. The mystery surrounding the outbreak has only deepened in the intervening years, giving rise to claims of conspiracies and cover-ups, as well as controversy over the official handling of the incident. For some people, at least, it seems canola oil’s reputation has not yet recovered.

And there’s another way in which the canola oil controversy links up with one of the all-time big hitters in the field of nutritional scare stories: genetically modified organisms, or GMOs. 

While edible canola oil was originally developed via traditional agricultural methods, the majority of varieties that are currently available in the US are GMO, having been modified to be pest-resistant. For some, this means they should be automatically avoided. But, and we can’t say this strongly enough, there is no good scientific evidence that genetic modification of crops poses a threat to human health. 

What are the benefits of canola oil?

So, we’ve established that a lot of the fearmongering around canola oil is just that, but does this type of oil have any special benefits?

“[C]anola oil is a safe and healthy form of fat that will reduce blood [“bad”] cholesterol levels and heart disease risk compared to carbohydrates or saturated fats such as found in beef tallow or butter,” said Dr Crosby. “Indeed, in a randomized trial that showed one of the most striking reductions in risk of heart disease, canola oil was used as the primary form of fat.”

Canola oil is suitable for inclusion in a so-called Mediterranean diet, because it’s high in an omega-3 fatty acid called alpha-linoleic acid (ALA) and naturally low in saturated fat.

It also contains high levels of omega-6 fatty acids. Whilst very high levels of these have been linked to heart disease and inflammation, canola oil strikes a good balance between omega-3s and omega-6s, which scientists consider to be optimal for the human diet. 

Is there any reason to be scared of canola oil?

In short, no. If you want to cook with vegetable oil, and canola oil is available to you, go ahead and use it. If you prefer the taste of it to other oils, go ahead and use it. If you’re allergic to other oils but canola would be safe for you, go ahead and use it. There’s simply no good scientific reason to avoid it – or any other seed oils for that matter – despite what might be cluttering up your FYP right now.

The content of this article is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of qualified health providers with questions you may have regarding medical conditions.  

All “explainer” articles are confirmed by fact checkers to be correct at time of publishing. Text, images, and links may be edited, removed, or added to at a later date to keep information current.