Myth: Olive Oil Breaks Down When Heated So Don’t Cook With It

I was recently watching a video where a cardiologist was attempting to debunk the on-again, off-again rumor that coconut oil is bad for you. He was reacting to a recent American Heart Association release where they said that coconut oil was absolutely bad for you and it raised bad cholesterol.

The doctor complaining about this, himself a member of the association, said that he cooked with lard, butter, and coconut oil because they are mostly saturated fat and thus stable when cooking. He seemed to think all other oils are completely unstable when heated, even in regular cooking.

So, he said, “I never cook with olive oil because it completely breaks down to trans fat when heated.”

Is this true? Is olive oil, since it is not a saturated fat, break down when heated and lose its health benefits?

Is Olive Oil Unstable When Heated?

Well, I’ll start by telling you I immediately stopped watching the video because the expert, in attempting to dispel one myth brought up another one!

I had no patience to try to figure out which of his further statements may be credible since he started with a complete, absolute, and authoritarian statement about olive oil that is untrue.

The same kind of authoritarian statement he complained about regarding coconut oil being bad for you. So, the short answer is NO, olive oil is quite stable when heated and does not break down into lots of bad things like trans fats.

Olive oil, unlike many other vegetable oils, even ones with higher smoking points, is mostly monounsaturated fat. Both extra virgin olive oil and regular olive oil will form a minuscule amount of trans fats when heated but not enough to significantly impact your health.

Trans fats are present in nature but used to be found in much larger amounts in margarine and vegetable shortenings.

Don’t Believe the Fake Olive Oil Hype

However, the fact that this cardiologist focused on trans fats from heating uncovers another leak in his theoretical dam. Trans fats are but one of the compounds that may be produced by heating oil, and not even the most significant.

A researcher more familiar with the problem would probably have mentioned something like volatile aldehydes and other oxidative by-products. Olive oil has been shown in at least one study to produce fewer volatile aldehydes than canola oil when subjected to cooking temperatures. 1

Heated Oil and Oxidation

When oil is heated, it is not only the heat stability of the oil that needs to be considered but its resistance to oxidation. Olive oil, due to its high amount of monounsaturated fat, not to mention antioxidant content, is more resistant to oxidation than, say, regular canola oil or high PUFA oils like sunflower oil.

In fact, in head-to-head studies with other common cooking oils, olive oil displayed higher stability under heat and better oxidative resistance, retaining its good qualities even with prolonged heating at temperatures used for deep frying…up to six hours. 2

Should You Keep Opened Olive Oil in the Refrigerator?

A Low Smoking Point Does Not Tell You Whether an Oil Is Unstable in Cooking

When you read about the dangers of cooking oils with low smoke points, keep in mind that the temperature at which an oil begins to break down does not correlate with its smoke point.

Oils with very high smoke points can begin to break down at lower temperatures than an oil with a lower smoke point, like olive oil. And the smoking point of olive oil is not as low as commonly believed and could be considered ‘moderate.’

Another thing to keep in mind is that when you fry foods over high heat using oil, bad things do occur. Those volatile aldehydes, for instance, will occur when you cook a steak on a stove using olive oil, butter, soybean oil, etc.

This doesn’t mean they are present in high enough amounts to be of concern to your health. Even in the above comparison of olive oil to canola oil, the fact that you will be exposed to fewer volatile aldehydes when using olive oil is good, but this doesn’t mean you should be mortally afraid of canola oil.

Can You Deep Fry With Olive Oil?

Olive Oil is GREAT For Cooking!

The fact is, test after test has demonstrated that olive oil retains its nutritional and health benefits even after being heated for ridiculous amounts of time.

One test showed that while not all olive oil is the same, olive oil in general is remarkably resistant to heat-induced breakdown and clearly a superior choice to most other vegetable oils, being able to resist significant oxidation for up to 24 to 27 hours of heating! 3

What’s more, there is evidence that when vegetables are cooked in olive oil, the phenolic and antioxidant compounds within the vegetables themselves increase. The type and proportion of these compounds vary depending on the characteristics of the vegetables themselves, and the type of cooking, but all in all, it’s a win for olive oil. 4

The take-home here is simple. Olive oil is very stable when heated and much more stable than most other vegetable oils. The next best, in terms of stability, are probably coconut oil and avocado oil.

The many health benefits of olive oil are well-retained when you use it for cooking. If you believe olive oil to be a healthful addition to your diet, then there is no reason to avoid cooking with it. Using it as a dressing or in an unheated state, of course, is also a very good idea.

None of this article is meant to compare olive oil with animal-derived oils such as butter or lard. It is meant only to address the myth that olive oil is highly unstable when heated under cooking conditions. Not only is this not true, but olive oil is exceedingly stable for very long periods of time even at heats used for deep frying.

Why Is Smoke Point Important?

The smoke point of an oil, as we’ve seen, does not tell you much about its heat stability. It also does not correspond to its ignition point or flash point, another source of confusion.

The reason the smoke point of an oil is important is that if you heat an oil beyond its smoking point, it will produce bitter, acrid and ‘burnt’ flavors. The plant-derived oil with the highest smoke point I know of is avocado oil, at around 520° F. That’s very high! And avocado oil is another great choice with its high monounsaturated fat content and abundance of oleic acid. But as an everyday cooking oil, it is quite expensive.