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 see NOTHING in this article about the formation of toxic aldehydes. Although this is fairly recent research i’d think someone writing on this site should know. SAD she does not.
    Perhaps she should subscribe to Dr mercola’s artcles…

  2. you say “the average home cook will never cook anything for 36 hours straight” referring to olive oil being heated to 350F.
    Well, stir frying requires heat way above 350degrees (I’d say 400, possibly 425) and degradation occurs at a specific temp (smoke point).
    350 is baking temp for a cake, 375-400 for a pie just as examples

    • The smoke point depends on the initial free fatty acid content of the fat, the lower the FFA, the higher the smoke point. Not all EVOO are equal! US’s national standard for EVOO is 0.8, California’s standard is 0.5 and some brand can have much lower FAA content, which means smoking point can reach higher temperature.

      The one I am using has been tested up to 490 degrees. I bake and cook with it without any problem.

  3. I was wondering the same thing about the temperatures. If you cook something at 350 for days, does the temp go significantly higher than 350? I think many people sauté at higher temps, and roast in the 400s. Not sure how the 350 degrees for a long period of time compares to roasting cauliflower with olive oil at 425 for 30 minutes. Does smoke point not matter? Still unsure about cooking with oils….

    • I would like to know the answer to the same question Carrie and Chris D posted. What about sauteing with extra-virgin olive oil because a pan on a stovetop can reach 600F degrees. I tend to avoid evoo for this reason when sauteing because it’s smells bad and then smokes. I use biodynamic/certified organic evoo and I don’t cook things at super high temps, but I do suspect damage can occur to the oil when cooking stovetop. So my question is, what temp is the max temp evoo is safe? Or should we let our nose tell us? If it smells off and it smokes, it’s safe to assume it’s no good.

      • You shouldn’t heat olive oil to the point where it smokes. Different varieties of olive oil have different smoke points, though, so I can’t tell you the exact temperature it will smoke. I would do some experimentation and see if there is a level you can cook it at without experiencing the smoking effect! You shouldn’t eat it if you noticed it smoking (and it won’t taste good anyway!).

  4. This was exactly what I needed to read today. I’ve been having a problem with coconut oil. It has been setting off supraventricular tachycardia episodes for me lately, so I’ve had to avoid it and cook everything with butter, which is also a problem because dairy products have been bothering me, as well. It’s good to know that I can finally go back to cooking with olive oil.

    • Butter burns VERY easily. French health experts have always warned about NEVER cooking with butter. OLive oil is clearly a better choice in this case.
      Lard from organic pork is another good choice.
      Tachycardia caused by coconut oil?? strange… Take additional magnesium!

      • Ghee (clarified butter, removing milk solids and water) has a higher smoke point than EVO, and less PUFAs (3.7%). I’d say very good for cooking. Anyway, I notice in all the mentions of temperature that no one suggests not to use such high temperatures to begin with. Gentle cooking, better food, better health-wise.

      • Chris, I certainly would like to know how you determined that using coconut oil caused your tachycardia. There is a statistical method to determine that but it takes a long time..

    • I meant warned about cooking with butter not about NOT cooking with butter.
      Butter should never be heated.
      Duck fat is another excellent choice for cooking and it is healthy

    • Regardless of whether or not there’s a connection between coconut oil and cardiac changes, there’s a difference between a fast heart rate (tachycardia) and SVT (much more serious). I’d recommend seeing your practitioner for an ECG and lab work, magnesium and potassium are a good start.

      • I’ve been taking magnesium for a year now, plus CoQ10, and other recommended supplements and digestive enzymes. I am having SVTs with nearly constant nausea, but the doctors don’t know why yet. Coconut milk and dairy also set these episodes off, as does anything with high fat content, like eggs and bacon. I have to eat very small meals to avoid getting sick. As far as I know right now, I do not have any kind of heart disease, but my last ECG was borderline. I just had an echocardiogram done today and have an event monitor to record episodes this month. Still waiting to hear the results.

        • I have just started with coQ10. Initially I supplemented with vit D for my irregular strong heartbeats (which started in the dark month of November). But only when I started balancing D with coQ10 and magnesium did I get relief from episodes.

          Today I make sure to go out in the daylight every single day ( this is the UK so sun is optional).

          My problem now is calcium ratio to magnesium. And Chris K of course recommends that we don’t forget vitamin K2, found in animal fat….which I have been cutting down on these last few years.

    • You are not the only one to get a trembly chest from coconut. Same thing happens to me. I am also dairy intolerant, so this is very good news for me too!

    • Hi Toni – thanks for your comment. This is exactly why I wanted to post this article. Some people have problems with other types of fats, so I just wanted to make sure people aren’t scared to cook with olive oil if they need some other options. Take care to get a good quality oil and make sure it doesn’t burn and you are all set.

    • I agree it sounds strange. Perhaps LONG-TERM exposition to oxygen and light can’t be compared to short-term heating

  5. Totally agree with PM, an excellent piece of investigative journalism in Canada a few years ago demonstrated that most olive oils are diluted with vegetable oils to lower cost. Personnally I buy the best stuff I can afford and drench all my vegetables in it but never cook with it. I use Ghee and coconut oil for cooking.

  6. At the top of the article you state: “butter (another saturated fat), which has only 60% saturated fatty acids, the rest of it being polyunsaturated fat.” Surely butter is 60% saturated, 26% monounsaturated and only about 4% polyunsaturated?

  7. Have you had any experience with macadamia nut oil? It appears to have all the benefits of olive oil (great omega 6 to omega 3 ratio, high in mono unsaturated, and it has a pleasant light nutty taste, rather than the strong flavor of olive oil, which simply does not lend itself to some foods.

  8. Makes sense since Med diet where they fo so much cooking in EVOO gets great healthy CVD reports in many atudies

  9. In England we have rapeseed oil which is a good alternative to vegetable oil. I have understood that it can be used for frying instead of olive oil because it has a higher smoke point (220C) so that’s what I’ve been using. It’s really nice especially if you get a cold pressed virgin oil but I’m happy to know I can go back to olive oil if I want. I don’t know what rapeseed is called in the US or what it’s omega 6/3 content is, I’ll have to find out.

    • http://www.marksdailyapple.com/healthy-oils

      Canola oil comes from rapeseed, a completely unpalatable seed rich in erucic acid, which is bitter and rather toxic. Canola oil is rapeseed oil stripped of erucic acid, as I detailed in this previous post. It gets a lot of attention from doctors as a “heart healthy” oil (one of the “good” fats) rich in omega-3s, but the fact that canola processing generally uses upwards of 500 degrees means a good portion of the Omega-3s could be rancid on the shelf.

      61% MUFA
      21% Omega-6 PUFA
      9-11% Omega-3 PUFA
      7% SFA

      • Sorry, I tried to wrap that above post in quote tags, which got eliminated. It’s all directly copied from Mark’s article.

  10. Some people are allergic to olive oil. Can be because of its salicylate content, or phloridzin, chlorogenic acid or gallic acid. I find that regular consumption of olive oil (not heated) makes me ill. I use macadamia oil with its almost zero polyunsaturated fat for salad dressing, and saturated fats for cooking.

  11. ‘Considering that the average home cook will never cook anything for 36 hours straight, I think we’re pretty safe here.’ From the other study, ‘Vegetable oil, on the other hand, was only able to go for 15 hours’. Using the same logic, because people will never cook anything in oil for 15 hours straight, that makes vegetable oil safe as well – we know that is not so.

    • “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. ”

      Yeah the logics in the article are a bit flawed in general. I think the take home point is awesome (i.e. olive oil is resistant to cooking damage), but you can’t say ‘as you know cholesterol levels don’t really matter ‘ and then point out LDL oxidation is reduced. Reduced oxidation is GREAT, everyone will agree on that. It has no further connection with LDL-levels in general, so why even mention familial hypercholesterimia?

      • I wanted to mention familial hypercholesterolemia because this population is especially concerned with heart health as they are more prone to heart disease. Thus, if olive oil is improving their heart health, I assume they’d want to know about it! But you’re right – it’s not specific to those with this condition – anyone will benefit.

    • So-called vegetable oils are already rancid due to high-heat processing. Actually, the whole process is rather disgusting — the separation process results in a gray, smelly oil which must then be chemically bleached, deodorized and coloring added.

  12. Eh. I never stopped cooking with olive oil, but it’s nice to know that I am fine doing it… I guess.

    CA Olive Ranch is a reputable company with good XV olive oil, and easily available at most supermarkets. I buy it at Costco when it’s available (seems to run out quickly)– $15 for a pack of two 1L bottles.

    Definitely spend the money on decent (actual extra virgin) olive oil, though.

  13. Now that we know olive oil is safe – can you look at the other cooking fats in Paleo land – namely lards and tallows?
    I’ve seen cited studies (suppversity blog) that note that, while the saturated fatty acid component of animal fat is stable, the cholesterol part is not and is prone to oxidation when used as a frying fat. Thus raising the question that repeated frying in lard may not actually be very beneficial.

  14. This article promotes cooking with olive oil but fails to advise what type of cooking is ok and up to what temperature. Many people will fry or bake above 350F so is this still ok? Most people can’t really monitor exact temperature while frying or sautéing. It is quite widely reported that the smoke point of extra virgin olive oil is 320F. What about this? No mention of smoke point and the fact that oils with polyunsaturated content can oxidise well before their smoke point anyway. This article is lacking and incomplete and if you plan to write an article advising people it should be thoroughly researched and more complete. Sorry just tired of reading contradicting opinions of people claiming to be experts. If you want more information about cooking with oils check out this article that I have seen. http://www.yogitrition.com/what-you-need-to-know-about-cooking-with-oils/

    • If you read the part where I described the studies that looked at olive oil, you’d note that they fried it for 36 hours (that’s a high temp cooking method) before it became unsafe. So yes, it is okay to cook at high temps, but I would always suggest (no matter what fat you cook with) that you don’t let it start burning.

      • It says 36 hours at 350 degrees – that is not high temp., just a long time. The article does say that they cooked at ” high heat, and only after 24-27 hours of frying (depending on the type) were they considered to be harmful.” but it doesn’t say what “high heat” is. Unfortunately I can’t read the full original source article without paying $35.

      • Kelsie I and many others would definitely not class frying at 350F high temp cooking. This is a poor article and there have been quite a few questions raised here by many which should be addressed.

        • Hi Terri,

          If you’re going to cook it at high temperatures, you’ll need to experiment with the particular oil you have as different olive oil varieties have different smoke points. I bake with mine in the oven at 400 F and have no issues as well as cook with it on the stove and have no smoking problems, but that may differ depending on the brand of olive oil you’re using.

    • I agree, some additional information on smoking points of oils and if they are the danger points would be useful. And deep frying with olive oil?

  15. This would be great news were it not for the additional fact that unadulterated olive oil is so expensive.

    Given that, I think that I will use organic lard, butter and coconut oil instead.

  16. good news! Is it still best to avoid using olive oil at higher temps than 350 F or would it be ok? What are the top fats to cook with in addition to olive oil?

  17. Thanks for that!! It has been distressing to read the many opinions against cooking with olive oil. It’s a lifelong favorite for this Italian girl and I am very happy to see some press in its favor 🙂

    • Me too, Gina. I am an old 97 year old Italian man. A lot of the cooking my mother did during the 20s and 30s was with plain old lard. But we had olive oil too. And I doubted that my parents (immigrants and uneducated) were sophisticated enough to know whether the olive oil was virgin or not. Being very young, .I was too dumb to know. .I’ve been using extra virgin oil (at least the bottle says so) for about 60 years now. I’m still ‘going strong.’

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