Is it Safe to Cook with Olive Oil?

Is it Safe to Cook with Olive Oil?

by Chris Kresser

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Olive oil is known for its health benefits, yet many Paleo experts say we shouldn't be cooking with it. Does olive oil stand up to the heat?

This is a guest post written by staff nutritionist Kelsey Marksteiner, RD. Click here to read her blog or join her newsletter!

Olive oil has always been a nutrition saint. Its health benefits have been touted for ages – high in antioxidants, anti-inflammatory, anti-cancer…the list goes on. (1, 2) Heck, even the USDA agrees the stuff is great for our health!

Yet there’s a popular myth circulating in the Paleo community that it’s unsafe to cook with olive oil; that it isn’t stable and oxidizes when heated, forming harmful by-products in the process. While this is true for other oils like canola and vegetable oil, I’m here to tell you that it’s okay to cook with olive oil. It has some unique qualities that make it stable under cooking conditions, and provided you’re buying high quality olive oil to begin with, you can sauté to your heart’s content.

Do you avoid cooking with olive oil? Here’s why you shouldn’t worry.

What is fat oxidation?

There are three types of fatty acids: saturated, monounsaturated, and polyunsaturated. What defines them is their structure; a saturated fat has zero double bonds (thus it is “saturated” with hydrogen), while a monounsaturated fatty acid has one double bond, and a polyunsaturated fatty acid has more than one. Check out the diagrams below and notice that the saturated fatty acid (left) has no double bonds, while monounsaturated fatty acid (center) and polyunsaturated fatty acid (right) have one and two, respectively. The double bonds are the “kinks” in the chain.

Double bonds are unstable when they come in contact with a number of elements, such as light, heat, and oxygen. While we call certain fats “saturated” or “monounsaturated,” the truth is that the fats we cook with are made up of many different types of fatty acids and we refer to them by their majority. For example, coconut oil (what we call a saturated fat) is made of 90% saturated fat. This differs from butter (another saturated fat), which has only 60% saturated fatty acids, the rest of it being monounsaturated and polyunsaturated fat. Soybean oil, on the other hand, is about 60% polyunsaturated fats. All of these differ from olive oil, which is made up of 70% oleic acid, a monounsaturated fat.

Because polyunsaturated fats have the most double bonds of all the fatty acids, they are more susceptible to oxidation. When polyunsaturated fatty acids oxidize they form unhealthy molecules called advanced lipid oxidation end products (ALEs). These ALEs cause an inflammatory reaction in the circulatory system, as well as the liver, kidney, lungs, and gut, and are thought to have negative impacts on human health. (3) This is why a Paleo diet excludes dietary fats with high percentages of polyunsaturated fats.

Why olive oil is less prone to oxidation

There are two reasons why olive oil outperforms other vegetable oils when it’s heated.  First, it contains polyphenols and tocopherols which act to protect the oil from oxidation. Second, it’s made up of mostly monounsaturated fat – remember, that’s the one with only one double bond, which makes it more stable in heat than fats with high amounts of polyunsaturated fats which have more double bonds. Between these two properties, olive oil can fry with the best of them.

It is thought that the phenolic compounds in olive oil – polyphenols and tocopherols – may influence olive oil’s stability in heat even more than its monounsaturated fat content. The phenolic compounds donate a radical hydrogen to alkylperoxyl radicals to form a stabilized radical. (4) For the chemistry buffs out there, this reaction works like this: ROO• + AH → ROOH + A•

One study fried olive oil varieties to see how they stood up to high heat, and only after 24-27 hours of frying (depending on the type) were they considered to be harmful. Vegetable oil, on the other hand, was only able to go for 15 hours. Despite lower amounts of vitamin E, olive oil still ended up less oxidized than the vegetable oil. The researchers also found that the polyphenol content of olive oil predicted its susceptibility to oxidation; varieties with more polyphenols were less prone to oxidation while those with less became more oxidized. (5)

Other researchers heated extra virgin olive oil to 350°F for 36 hours (yes, you read that correctly. 36 hours!) and found that while there was some degradation in the phenolic compounds content, the oil kept most of its nutritional value. Considering that the average home cook will never cook anything for 36 hours straight, I think we’re pretty safe here. (6)

Another study compared insulin sensitivity in obese, insulin-resistant women when they consumed foods fried in extra virgin olive oil to meals that contained uncooked oil. This one surprised me as it compared the cooked vs. uncooked olive oil, and cooked won out. There was no difference in insulin sensitivity when the oils were eaten by lean subjects, however. This was a small study, but it’s intriguing to hear that perhaps the cooked olive oil may have some benefits over uncooked oil for some people. (7)

Being able to heat olive oil opens up cooking options, especially for those who are very sensitive to the effects of saturated fat on their cholesterol levels. If you’ve been hanging around ChrisKresser.com for a while, you probably know that your cholesterol levels aren’t the end-all-be-all. However, those with familial hypercholesterolemia (and even those without!) will be happy to hear that they can cook with a fat that has been shown to reduce LDL oxidation, thus improving their heart health. (8)

How to buy and store olive oil

While the fact that olive oil contains mostly monounsaturated fatty acids is important, researchers believe that it is actually the phenolic compounds that stabilize the oil as it’s heated. This is why it’s vital that you purchase extra-virgin olive oil versus pure olive oil. Extra-virgin olive oil goes through less processing – it’s simply pressed and does not go under any heat or chemical treatment. Olive oil is one of the only oils that Americans still consume relatively unprocessed; most of the oils we buy are refined. Pressing the olives retains many more nutrients, including phenolic compounds, which we know serve to protect olive oil from heat. Even better is extra-virgin olive oil that hasn’t been filtered – the particles that cause the oil to be cloudy also act as antioxidants and buffers against acidity, thus protecting the oil from oxidation. (4)

That said, much of the extra-virgin olive oil bought in the United States is adulterated with other oils like soybean or rapeseed. That’s a bummer considering that many of us like to purchase our olive oil when we go to the grocery store. Thankfully, olive oil expert Tom Mueller has a list of extra-virgin olive oils you can buy at your local grocery store (including the real deal from chains like Costco, Trader Joes and Whole Foods). Make sure to check that out and if you’d like to learn more about this issue, read Mueller’s book Extra Virginity: The Sublime and Scandalous World of Olive Oil.

The other option, of course, is to source your own olive oil from a company you trust. If you live in a climate that supports olive growing, you might even be able to find a local company to buy from. If not, there are a plethora of options online, and it simply becomes a question of researching the company and preferably talking to a representative to see how they process the oil. A popular one in the Paleo community is Kasadrino’s olive oil – you can learn more about their company and values by heading to their website.

Once you’ve got your hands on a quality extra-virgin olive oil, take care to store it properly. Remember that heat is only one of the elements that causes fatty acid oxidation, the others being light and oxygen. You should store your olive oil in a cool, dark place in a dark airtight container. (Don’t buy olive oil that comes in a clear container, especially if you suspect it’s been sitting on the shelf for a while.) If you purchase large tins of olive oil, pour out what you’ll use in a few weeks into another dark bottle so that you can avoid opening the tin often and exposing the oil to oxygen.

Here’s the bottom line: extra-virgin olive oil is perfectly safe to cook with. It stands up well to heat due to its monunsaturated fatty acid and phenolic compounds content and fares much better than other vegetable oils. It’s a great oil to eat both in taste and health and shouldn’t be avoided. However, it’s not the only healthy fat out there! You should always consume a variety of healthy foods, fats included.

So what do you thinkwill you start cooking with olive oil?

Kelsey MarksteinerThis is a guest post written by Kelsey Marksteiner, RD. Kelsey is a Registered Dietitian with a Bachelors degree in Nutrition from NYU and a Master’s in Human Nutrition and Functional Medicine. She works in private practice and recommends individualized dietary therapy focusing on biologically appropriate diet principles to aid her clients in losing weight, gaining energy, and pursuing continued health. She is a firm believer that everyone is different, and she tailors her plan for each and every individual. Through her work, she aims to meld the dietary wisdom of traditional cultures with the latest science in integrative and functional medicine to create plans for her clients that work in the modern world. You can learn more about Kelsey on her staff bio page, or by visiting her private practice website. Join her newsletter here!

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  1. If someone states that olive oil is healthy or that they are a Paleo expert I move to another article.
    Opinions are great if I do not know what time it is but my daily nutrition is based on studies that apply science.

  2. Cook with olive oil, don’t cook with OO, die from using OO, live to 105 using OO, fry with OO, don’t fry with OO, get extra virgin, organic cold pressed, don’t waste your money, use tallow, lard or duck fat, saturated fat will kill you, saturated fat is good for you, mono is the best, no poly is says vegans, drink 12 glasses of water, don’t drink except when you’re thirsty, eat meat, don’t eat meat, drink milk, don’t drink milk, eat only organic but even organic is often not organic but when it is it often has some pesticides, eat veggies but hardly any, eat many like bowls and bowls, eat white rice, don’t eat white rice. I could write 1000 plus pages on the controversy, the opinions, they science, the results, etc., and when I got done I’d go jump off a bridge without a parachute.

    • Agreed!! Pull up a Google search on any of those things & there will be those who say it’s good & those that say it’s bad. And the people that recommend olive oil or fresh fruits & vegetables say we can’t get just any kind of these but organic, grass fed, non GMO from these upscale grocery stores that most of us can’t afford to go into much less buy the stuff in there. We can barely afford the food in the regular grocery stores & still pay everything else. And the authors of these articles just happen to have an online store selling these things at huge prices. The stress of trying to eat “right” & afford it will cause increased stress in a person which they also say causes disease. Seems like defeating the purpose to me. I’ve decided to just eat the best I can with what I can afford & not worry about it. Maybe us fearing & worrying about something happening to us might just bring it to us. What we fear we create.

    • Yes, the myth of the benefits of olive oil has been around for generations. Did you ever read a study of what happens when you cook with an oil, be it EVO or any other oil????

      Have you read the studies of what proves happens to your arteries after you consume olive oil even without cooking it?

      Ohhh you rather follow the myths…ok with me, good luck!

      Amazing how many people insist that EVO is not a refined oil. Does it make any sense to you that maybe consuming whole olives would provide the benefits you claim for EVO????

  3. Hi Chris Kresser community. Chris’s book and the paleo lifestyle has completely healed my body from illness at the age of 26+. I would like to have someone confirm whether olive oil extra light is safe to use for frying and cooking with? It’s been difficult to find a correct answer on this one as it has a high smoke point but is not extra virgin olive oil. I’m from the UK (not in mainstream paleo US.. Haha) so if you could offer comments and any help/advice would be much appreciated. Thanks

  4. Great article! My mother has hereditary cholesterol issues, and I’m helping her change her diet the Mediterranean Paleo diet suggested by Chris Kresser. Do you have cooking oil suggestions other than olive oil that would fit the more monounsaturated, less saturated prescription? My mom likes olive oil, but she is Japanese, and she’s going to want something with a more bland taste for most of her cooking. Any suggestions would be greatly appreciated.

  5. Thank you for this article, it cleared up so many of my misunderstandings about olive oil and my husband will be thrilled to know he can cook with olive oil again!

      • Have you looked at the Ikarians, who swim in olive oil. Fry like madpeople and eat grains. They have far more over 100s than even the okinawans–in fact than any other group in the world. They are top of the blue zones. It’s not genetic either since those who move away get cancer and sick. There are ikarians who have acquired disease, moved back and recovered and lived until over 100. If you spend 10 years reading paleo, then everything that spins off from it, from all the ancestral health bloggers and then also cutting edge scientists, you will eventually realise we know absolutely ZERO. Everything you thought was true and certain is not. We can’t rely on scientists to give us a culture of food and therefore health, based on them working it out as they go along. The ONLY thing we can do intelligently is to look to people groups that are not agonising over their every last morsel and doing very well, considering everything against them. Then imitate those peoples to the best of our ability, without guilt or fear.

        • The 10,000 Ikarians do well but that does not prove the olive oil is a factor. You omitted the fact that they eat six tmes as many beans as the average US consumer and far less meat and processed foods.
          You follow your opinions and I will go with the best science of the day.

  6. Always have and always will cook with olive oil. My family are Portuguese and this is a staple. It never made sense to not cook with it. I agree with the quality being important and storing it properly. If I am however cooking something on very hight heat…which is so rare, then I use coconut oil 🙂

  7. Question: what about ROASTING with extra virgin olive oil at 425 degrees Fahrenheit and over? That is significantly higher than the smoke point of olive oil and commonly used to roast many vegetables like sweet potatoes, asparagus, peppers (500 degrees). Is this safe?

    • Why not just use something you know is safe? Like real butter (preferably from unpasteurized milk), or home-rendered lard or bacon grease? Why keep fussing around with any of the “oils” when you ALL keep questioning if they’re safe to cook/bake with? To me, that just doesn’t make good sense.

      • Some of us have food allergies to dairy and additives (I haven’t used butter in six months), and others want a more healthy, cleaner fat/oil because of issues like high cholesterol (even at 102 lbs I struggle with it due to genetics). And if you find a substance that has potential additional health benefits, you want to find out more about it.

      • JD. Smith,

        Just out of curiosity, if you’re going to use butter at temps of up to 500° why would it matter whether the butter itself was raw or not?

        I agree with you though, at high temps, animals fats are always best and (Karen) they are certainly “clean” when the animal is pastured and raised organically– and do not worsen serum cholesterol.

    • If you buy “genuine” EVOO which has 0.3% or below acidity etc…. 425 should not a big problem. no smoke whatsoever.

      I rarely bake my food with 500F or 260c… I cannot answer you for that…

  8. This is one topic that generates a lot of confusion and I wonder if anyone can clear this up. Doctors such as Ornish and Essentyn swear that ALL oil is heart damaging and the med’ diet is healthy despite olive oil and not because of it. In other words if we cut the oil out the med diet would be even better. We then get people like Dr Sintra saying Olive oil is wonderful and we should consume it by the spoonful. Somebody has to be way off the mark here but who ?

      • That article is full of shameful information meant to push what sounds to me like a total vegetarian WOE (way of eating). What we are finding nowadays is that saturated fats like butter and real, home-rendered lard made from the leaf-lard, ghee and some of those things are so much better for us than bottled oils of any kind. Personally, I’ve been a believer in the high-fat/saturated fat WOE for my whole life. I think we’d all be healthier if we stopped believing everything that comes down the pike from these so-called “nutritionist comment sections” (you know, like the one you’re reading now).

        Cholesterol is good for people, especially as they age. Keeping some meat on your bones is more important than current BMI trends, which are usually so bogus as not to mean a thing in reality. The plain fact is, people with higher cholesterol live the longest. PERIOD. Stay away from doctors who are constantly wanting you to believe that cholesterol blood tests are actually worth something in terms of your health – they aren’t.

        Read at Dr. Malcolm Kendrick’s blog. Read at the THINCS.org web site. Read at Weston A. Price.org web site. Those are the places you will find TRUE information about how to become and stay healthy. Sometimes you do everything you can and your health still goes south. It happens. We simply must learn we are not in control all the time. Just do the best you can, but learn from the right people.

        That’s my advice, take it or leave it.

        But reading junk like that pritikin article is inexcuseable, much less believing what’s in it. The program that has it the closest to being correct is Dr. Atkins.

        • The logical conclusion from the above article would be to consume saturated fats as they are less prone to oxidisation. Coconut oil would therefore seem to be the oil of choice if one is to use an oil and not Olive oil

    • The Pritkin Institute are also behind Ornish and Esseltyn in that they too state that Olive oil is artery damaging and should not be used heated or otherwise.

    • Nothing seems to create a greater silence than this oil topic. I have asked numerous supporters of Olive Oil for a confirmation of their beliefs in light of the opponents and most seem to go quite. Whether they are just careful of being guilty of a huge howler I don’t know. The best I got was from the Dr running the healthy heart summit. He cited as evidence a resent Spanish study but this study seemed to only show that a med diet with oil was better than a low fat diet and a med diet with oil and nuts was better than both. What it did not demonstrate was whether a med diet without oil would trump all three. There is also a tendency to support oil with population evidence or lipid profiles neither of which is very reliable.

      • Ohhh you are on to a dark secret that many companies do not want you to broadcast….no oil is healthy, some are less harmful than others.
        However, if you are one of the many addicted to oils, salt and sugar facts do not matter…

    • never rely on those best selling auther Dr. “WHO” for nutirtion advises… many things they said are usually over-simplified, just treat them as “book sellers”

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