Is it Safe to Cook with Olive Oil?
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Is It Safe to Cook with Olive Oil?

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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?

is cooking with olive oil safe
Olive oil is a common cooking oil. Volosina/iStock/Thinkstock

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!

204 Comments

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  1. I have read that the heat of frying “damages” the omega-3 fats in olive oil. Can someone comment on that?

    • According to David Khayat, renowned French oncologist, the omegas can even become unstable when exposed to light, transforming good unsaturated fatty acids into carcinogenic agents. This is true for heating oil to high temperatures as well, as the fats change and become unhealthy.

  2. While I agree with the argument that olive oil is better than other vegetable oils, you make a big citation error. The abstract of the study you cited where you said the oil was heated at 350 degrees for 36 hours actually says it was heated at 180 degrees. BIG difference, especially to our health. It makes me question your other points. The other studies don’t even say what temperature they were heated at in the abstract, and I can’t read the whole study because I’m not a subscriber. It makes me angry when people are so loosey-goosey in their information and it effects people’s health when they are believed and trusted. EVERYONE, do your OWN research! Don’t take people at their word!

    • Please understand metric conversions without jumping to wrong conclusions. The study says 180 celsius, which equals to about 355 degrees F…

    • Lily, please do all of us a favor and just google the conversion of 180 C to Fahrenheit. Also Affect (verb) = to cause harm / Effect (noun) = consecuence . It is a shame that the educational system failed you.

      On the other hand, the article was great, very resourceful. I appreciate that Chris used footnotes to explain each point given.

  3. Hi, can I just ask, if olive oil is protected from oxidation via heat because of its natural composition, why do we need to store it in a cool place? Surely it will be fine storing it in a kitchen cupboard?
    Thanks,
    Mark

  4. Hi Chris,
    You mentioned saturated fats and them having an effect on cholesterol whether one has a fx history or not… The Hearst foundation has always said it does have a considerable effect and steered us to oils like olive and canola yet recently there is info that contradicts this and says oils like in butter and coconut oil and other saturated fats are good for you and have no impact on high cholesterolaemia?
    Could you comment or post a comparative study on a list of ideal/not ideal oils to consume and especially cook with??? It’s all so confusing when u read articles that conflict online

    Also you mention EVO oil can be cooked for upto 36hrs before being denatured… Does that mean oil used fr frying should not be reused time and time again as often ppl do? Instead to use fresh oil every time..

  5. I always questioned the advice of the paleo health experts advocating against using olive oil as a cooking oil, simply because those people on that mediterranean diet seem to live the longest and I imagine it’s their go to cooking oil.

    • Hopefully some of the health leaders in the paleo community will revise their recommendations for acceptable cooking oils. I can finally not feel guilty when consuming cooked olive oil, you took some weight off my shoulders, Thanks for the valuable post. This site is a cut above!

      • He cited the study wrong. DON’T heat it above 180, as the study he cited ACTUALLY says. (click on the 6 and you will see the abstract yourself)

        • Lily, learn the difference between degrees Farenheit and degrees Celsius, preferably before you go round the internet, ironically accusing people of being inaccurate.

  6. The hard part is finding any oil besides coconut that doesn’t smell rancid from the get-go. Olive oil is particularly rancid smelling, no matter how many virgins or extra virgins are in the name.

    I don’t use a lot of coconut oil either, but use real butter instead. I don’t fry a lot of foods, but I roast a lot of root vegetables, and brown onions in a roaster in the oven, etc., so it’s nice to have butter as my foremost choice. It would be nice to find a decent oil to use with my homemade, flavored vinegars on salads, though.

    I’ve also recently learned to make cooked mayonnaise rather than the stuff you need the blender for, which always seems to include olive oil in the recipe. Some olive oils I’ve tried in years past had a very strong flavor and didn’t work well.

    Also, if you want the real scoop on eating a REAL Mediterranean diet, you need to check this out:
    http://www.tendergrassfedmeat.com/2010/10/05/call-it-medical-not-mediterranean/

    • Maybe try to get EVOO that has low acidity ( at least 0.4 or below) and K232/K270 ( 1.6 and 0.14 or below) etc. Also, certified destination of origin for the olives that were being used to produce the oil is also important.

      Oils that only have “Product of Italy or Spain” etc written on it instead of a specific region in Italy/Spain as well as the name of the producer are most likely mass production low quality EVOO… some of them do not even reach the EVOO standard… ie acidity way above 0.4% or even above 0.8% US

      Personally, I don’t buy big brands olive oils from supermarkets, they taste bad…..

  7. If Chris Kresser is okay with using Olive Oil out of ANY bottle for cooking and eating ANY fried food at all, I can’t take anything else on this website seriously. How disappointing.

    Do your research!

    • Not all extra virgin olive oil are produced equal, the lower the free fatty acid % contained in the oil, the higher the smoking point tends to be. What she was saying about double bonds etc are right, one thing she could have mentioned is the relationship between free fatty acid content and smoking point.

      The US standard for EVOO is 0.8% but you can get great quality fresh EVOO from reliable manufacturers that has 0.5 or even 0.3% FFA. Good quality EVOO like this is ok for normal “pan fry” at home. I use it for baking as well at 220 degree c, no smoke whatsoever!

      Extreme heat frying or deep fry are always not healthy anyway, I doubt any oil can be healthy if you cook like this!
      maybe you should do some research, too. Peace!

    • I’m with you, he even cited the study wrong. DON’T heat it above 180, as the study he cited ACTUALLY says. (click on the 6 and you will see the abstract yourself)

  8. My husband is Italian. When he heard me first say it’s not healthy to cook-heat up Olive Oil, he fired back- “So people who live well over 100 on the mediterranean diet don’t cook with olive oil?” It made me scratch my head and think, he’s got a point! I cook with olive oil all the time now without guilt. Glad to see this article!

    • There are lots of different coconut oils & I, as a great fan of coconut oil, can’t stand certain brands. I simply keep looking until I find one that smells & tastes so good that I also put it on my skin.

    • Yes, absolutely, but they mostly use it at “sauté” heat level. Which genuinely Italian ( c.f. American influenced) dish is deep fried? Even a real “Italian” pizza (note the name, from piazza) is only ‘al forno’ for a few minutes.

      • “Even a real “Italian” pizza (note the name, from piazza) is only ‘al forno’ for a few minutes.”

        Yes, but that’s at 1,000 degrees F ! A real Italian pizza oven is very different from anything in America.

    • I am Italian, first generation of immigrants of early 1900s. I made it to 97. I use Olive oil freely, in salads, frying, cooking and have done so for years. In the Depression years we ate whatever we had and it wasn’t always what today I call gourmet. In my six years in the Navy (WW2) I ate whatever the Navy could serve shipboard under the circumstances and that wasn’t always pretty.. However, over those years the food ‘experts’ cited Trans fats, Canola oil, Vegetable oil, Peanut oil, etc. as the oil de jour. Since then (for about 70 years) I used mostly olive oil. And currently I also use coconut oil and butter freely. All the above does not explain my longevity (which is probably the basic issue we think about in these forums even though we don’t say so. Frankly, I am tempted to say, “to Hell with it, eat what you want,” with a caveat, “depending on how old you are.” And if you are old enough to hesitate to buy green bananas, I say, go ahead buy them green but make sure you eat them fast (just in case.)
      I do have one rule, notwithstanding my age: Don’ let any cooking oil smoke (either cigarettes or cigars.)

    • The five Blue Zones were the largest number of people that do actually live to be over 100 do not use olive oil.

      Greece, the largest consumer per capita of olive oil in the world, has more heart disease than the dear old USA which everyone knows has a terrible diet and loads of heart disease.

      BTW, take a trip to Italy and you will see many obese and overweight people there…

  9. Really really well written, Kelsey. And such important information for those out there seeking to understand their bodies and optimum health. It answers the question of why, if cooking with olive oil is bad for you, have we touted the Mediterannean diet and it’s benefits for longevity and long health. Again, I applaud your information and writing style.

    • oh well, at least it’s not a grain oil.
      BigPharma says ‘everything in moderation’.

  10. So true about quality olive oil. I have found it hard to find truly “unadulterated” olive oil in the stores. If anyone is looking for a quality EVOO, from a trustworthy company, I discovered a gem. Etateolive.com, offers the purest olive oil on the market, straight from small farms in California. It is the most amazing olive oil I have ever tasted. The Koroneike is orgasmic! Highly recommended.

  11. What’s healthier? Cooking with conventional ghee from grain-fed cows or butter from farm cows fed grass? I’ve tried coconut oil, but it tastes nasty. I like olive oil, but I didn’t cook with it, because I thought that was bad.

    • Strange you consider coconut oil as ‘nasty’ tasting. That is all i use for cooking and found foods absorb less of the oil and hash browns taste much better!

      The negative I have found is that it is solid if temperature less than 72F!

  12. There are a few valid queries appearing repeatedly in the comment thread that seem to be completely ignored by Ms. Marksteiner. Disappointing.

    Anyhoo.
    Bottom line, when cooking with fats/oils and keeping it healthy, conscientious buying and storage matters, but what matters most, arguably, is the smoke point. That said, I found this article much more useful: http://www.seriouseats.com/2014/05/cooking-fats-101-whats-a-smoke-point-and-why-does-it-matter.html

  13. All sorts of problems w this article, but one I see, glaringly apparent, is the ‘byline’ says “Chris Kresser” then at the end it says it’s written by someone else.

    Change it. It’s not true and lends to the inaccuracies in the article.

    Thanks.

      • No, at the *very* beginning it says “By Chris Kresser.” And I pulled it up because I got the excerpt in my email with Chris Kresser’s photo at the top, Chris Kresser’s signature at the bottom, and no mention of any guest contributor anywhere.

    • This was a recent decision by Chris – it is for SEO purposes so that people can find these articles when they search his name. It is very clearly marked as a guest post, however, so not sure what the issue is.

      • So you mean this is a deliberate bait-and-switch decision? Hah. I’m a fan of this site, but now double disappointed: 1) not impressed with the rigor of this article (not saying that the conclusion is wrong, but I couldn’t draw it based on the sparse, though sciencey-looking, arguments), 2) this “SEO” issue.

  14. I’ve been cooking with it for years without any issues but I just recently purchased lighter olive oil made specifically for cooking. Tastes very good with a bit of butter.

  15. My cholesterol has risen from a great 3.7 to a less great 4.4 over the past year. I think the major change in my diet and lifestyle over this time was swapping from cooking in coconut oil and lard to using mainly refined (light) olive oil because I thought it had been given the thumbs up. Now I’m wondering…

  16. I am not sure about this article. Coconut oil seems like a gift from nature to fry with. It’s almost entirely saturated and very stable in nature to degradation of all kinds (heat, light, and air). Frying a whole lot might not be a great idea anyway, but when I do I will stick with coconut oil. Olive oil seems like perfect salad oil to me.

    • There are people out there who don’t like coconut oil or have other dietary restrictions that lead them to seek out other options. Olive oil can be one (of many!) other options out there.

      • I wonder of it’s worth compiling a list of oils good for cooking (high temps) down to those to avoid. Seems like many out there are still confused – as I am.
        Does coconut oil used in curried or cooking at high temps for a log time warrant high saturated fats and equate to high cholesterol?

  17. Here is an interesting tidbit about olive oil. Disclaimer, I’m a certified diamontologist and this information was learned whilst being certified. Olive oil because of it’s high heat tolerance is used in the diamond cutting process.

  18. please can you clarify about where the smoking/boiling point to oils comes into this.

    Also what about ‘cold extraction’ do we need to take that into consideration?

    I have heard before that while unfiltered extra virgin with all the phenols is great for eating raw that we should use light olive oil for cooking. Is there research for this side of the argument too? Or is that just guesswork that people have come up with?

    Interesting point someone brought up about formation of toxic aldehydes. Would that be through heating all oils? Or are some spared?

    This article is really interesting but needs a little more clarification to be completely integratable.

    I would love to hear back on this.

    • Would be happy to! You don’t want any oil or fat to be smoking – not only does it taste terrible most of the time, but it’s also not good for us.

      Different extra virgin olive oils vary in their smoke point due to a variety of factors, so truly it’s something I just keep an eye on in the pan. Don’t walk away from it only to have it smoking when you come back!

      I do not recommend using light olive oil, as it’s been processed. Real food all the way!

  19. Thank you, Kelsey, for this insightful article on cooking with olive oil. I have continued to, despite the negative press, because I could not find an alternative. Great to know that olive oil is the one to go for!
    I really enjoy your articles and have found your information very helpful, especially this one and your one on FODMAPS.
    Thanks!

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