Oils For Cooking: Which Ones Should You Avoid?


by Alejandra "Alex" Ruani — Get free science updates here.
oils for cooking

Photo Credit: flickr

First of all, you don’t need to be a chef to benefit from today’s article. I’ll answer a common question so when your client asks, you’ll be able to give them the best information possible.

Let’s run a little test:

  • Which oils are you (or your client) cooking with?
  • Why are you (or your client) using those oils?
  • Do you think there are better options?
  • And which oils do you believe you should avoid?

When it comes to cooking, not all oils are created equal.

Here’s the bottom line: some oils are better suited for cooking than others.

Why?

Simply because they can handle the heat better, making them less dangerous to your health. And that’s a big deal, especially when using higher heat.

With that in mind, the context of today’s article is the toxicity, oxidation, release of free radicals, and degradation of oils for cooking (rather than heart health, or weight loss, or everything else under the sun).

Smoke points and harmful free radicals

The first question you need to ask yourself is: which oils create harmful compounds when heated?

Let’s start with the smoke point first.

The smoke point of an oil is the temperature at which it goes over the edge of safety and starts smoking.

When an oil is heated past its smoke point, it releases free radicals – it reacts with oxygen to form harmful compounds. You definitely don’t want to be consuming or breathing in these.

Free radicals can injure cells and DNA in your body.

Beware of HNE, a nasty compound

One harmful compound that can be produced when heated is called HNE. This compound is linked to the pathogenesis of vascular diseases such as atherosclerosis, diabetes, and neurodegenerative disorders.

The nasty thing with HNE is that the longer you heat the oil, and even the more you reuse that oil, like restaurants do, the more HNE it will accumulate.

Bad for the body.

Plus, when it comes to oil reuse, this is a great opportunity to truly limit your eating of fried foods, especially in restaurants. Restaurants commit two bad acts:

  1. they typically fry in polyunsaturated fats (you’ll learn why this is not ideal in a moment) and
  2. they reuse the oil over many times.

Keep in mind that our human body is quite capable of defending itself from toxic or unsafe compounds that enter its space. The best line of defence that you can consciously choose for your well being is to minimise exposure to noxious compounds such as these.

Oil stability is revealed in saturation levels

Regarding the saturation level of fats in cooking oils, consider the types fatty acids they have. This will give you a big clue in both their heat tolerability and overall stability.

Oils with saturated fatty acids are the top choice for cooking. These oils are olive oil, avocado oil, clarified butter (ghee), refined palm oil, and coconut oil.

They are stable because the fatty acids are basically packed tightly together. They’re not loose, in other words. They can tolerate high heat well.

At the other end, there are oils with polyunsaturated fats. These are oils like soybean, corn, canola, sunflower, and safflower. They’re unstable fats – they’re not bound together tightly at all. Because they are unstable, they can produce higher levels of free radicals when they’re heated.

And, as we said before, we don’t want too many free radicals in our bodies.

What is ‘high heat’ cooking… and why should I care?

Higher heat cooking is used for sautéing, frying, stir-frying, grilling, pan roasting, searing and caramelising.

The real big important consideration here is: what happens to the oil when it gets too hot? This is where you want to be considerate of the type of oil you’re using.

When it comes to using oils for cooking, you have choices to decide upon.

As mentioned previously, you can use oils with stable fats, such as olive oil, avocado oil, clarified butter (ghee), refined palm oil, and coconut oil. This is a healthier way to heat your foods, because oils with saturated fats are pretty resistant to heating, which means less degradation.

The oils which should be avoided for cooking are oils like soybean, corn, canola, sunflower, and safflower. These oils have unstable fats and will decimate the nutritional properties of your food. Oh, and they’ll give you a big fat health risk in the meantime.

Cooking with oil 101

Heating oil up until it smokes is a really bad idea anytime if you want to keep things healthy.

Here’s a scenario that you or your client might be able to relate to:

You turn on the heat on the stove top, put some oil into your pan and get distracted by something outside the kitchen. Next thing you know smoke is everywhere.

Sound familiar?

If you’re cooking at high heat for say sautéing, grilling, or pan searing, the salient point to remember is to use oils that are stable and have a high smoke point.

That means they have more stable fats, or saturated fats, in them to tolerate the high heat better. I’ll give you a complete list below so you can be clear.

Okay, in summary, which oils should you use?

Based on the above, here are the best cooking oils to use in the kitchen in order to reduce free radical exposure and toxicity.

The simplest way to break this down is by the level of cooking heat you are using.

This first group is for high-heat cooking. These are specifically for frying, sautéing, grilling, pan roasting, searing, stir-frying, and caramelising. Here are a few safe choices:

  • light or refined olive oil (here the word ‘refined’ means without the combustible solids found in extra virgin oil, which can degrade into harmful oxidation products during high-heat cooking)
  • avocado oil
  • clarified butter (ghee)
  • refined palm oil (here the word ‘refined’ also means without combustible solids)
  • coconut oil

All of the above have a higher smoke point and are lower in polyunsaturated fats.

If you are leaning towards just medium-heat cooking, such as gentle sauté, stewing, baking, or braising, all of the above would work, as well as butter.

Free Download

Click HERE to get our Oils For Cooking Workbook (PDF download) that will help you work out if the oils you're currently using are suitable or not.

Remember, for both high-heat and medium-heat cooking, look for a cooking oil that meets both of the following criteria:

  1. LOW percentage of polyunsaturated fats (15% or below), and
  2. HIGH smoke point (160 °C or above).

How about off-heat options, such as over a finished dish, after it's been cooked?

For maximum flavour, you can go for unfiltered extra virgin olive oil and unrefined or toasted nut and seed oils.

Care for your oil: avoid these two things

When taking care of your cooking oils, there are two additional things to remember (besides heat and saturation). These two things are:

  1. oxygen, and
  2. exposure to light.

Why? Because they negatively affect the oils and can cause them to become rancid.

Rancid oils are a major source of destructive free radicals in our diet and they shouldn’t be consumed.

So, what should you do then?

Store your oils in a cool, dry place, away from direct light. You don't want them to oxidise and go rancid.

Also avoid buying in large containers. Buy smaller batches, so the oil has less 'sitting around' time and stays fresher.

Oh, one more thing – tighten that lid before storing to keep them cared for best!

Now, back to you!

Were you aware of this information regarding oils for cooking? What's been your experience?

What have you or your client been using so far? How can that change?

Hop in the conversation below and let us know. Share this with someone who could use a quick lesson!


Every other Thursday we share our research and actionable advice to help you and those you care about. If you enjoyed this, join our FREE updates.

54 Comments

  • Helen

    Reply Reply September 11, 2014

    I have heard that Canola Oil is bad for you as an unstable fat. I have also heard that this was a rumour that was started and there is no truth in this. I have a flat belly diet cook book and Canola Oil is used frequently as a MUFA (monounsaturated fatty acid). Can anyone confirm categorically if this is a good or bad oil.

    • Alex

      Reply Reply September 11, 2014

      Helen, each oil you use has a combination of saturated, monounsaturated and polyunsaturated fats. The most stable oils for cooking are those with: A) a low percentage of polyunsaturated fats, and B) a high smoke point. Canola oil is one third polyunsaturated fat, which makes it less stable for cooking (it oxidises/degrades faster when heated). Have a look at the table in our “Oils For Cooking Workbook” and use the criteria above (A and B) to spot the most stable ones: see the Oils for Cooking Workbook™. I also wanted to say that the context of today’s article is toxicity/oxidation rather than weight loss, I think it’s a very important distinction to make, so thanks for sharing :-)

  • Jacque

    Reply Reply September 11, 2014

    Hi, great article thanks for sharing. I was of the understanding prior to reading this that Olive oil was not a good choice for really high heats? Could someone please clarify this for me. I personally tend to use Olive oil on my salads and Coconut oil for my high heat cooking, does anyone else do this?
    Thanks Jacque :)

    • Alex

      Reply Reply September 11, 2014

      Thank you, Jacque! There’s only one study that found a problem with olive oil becoming unstable, but this was deep frying for 8 hours a day for 5 days with the same oil. Nobody does that, except restaurants and commercial frying operations. If you’re not using animal products, coconut oil is one of the best/most stable in heat :-)

  • Natalie

    Reply Reply September 11, 2014

    I don’t cook with olive oil especially not refined. Adding the word refined to any foods just like the sugars and carbs is not good. Your oils should always come in dark bottles & even a box if its top top quality. If you read the book fats that heal you will never bad mouth butter again.

    • Alex

      Reply Reply September 11, 2014

      Natalie, the word “refined” in this case indicates the removal of any solids in the oil or reducing the amount of combustible components that can catch fire or burn, that’s why refined oils have a higher smoke point. However, back to your concern, it’s probably best to avoid processed/refined oils that have gone through a heat process during refinement, where some of the oxidation and degrading could have happened before you bought it. So when you look for a refined oil to cook with, go for cold pressed or expeller pressed, which means it’s been mechanically processed, as opposed to heat treated :-)

      • jill

        Reply Reply August 9, 2015

        Recent studies (sorry I don’t have them in front of me) say that expeller pressed oils are not good because toxic chemicals are used to facilitate the process so the more unrefined and organic the product, the better in general for health. Canola is a rapeseed, isn’t it? Canola stands for Canadian Oil and I’m pretty sure rapeseed is GMO. If anyone knows that for sure, I’d love it! Also, no (refined or otherwise) palm oil is a good choice because Palms are being over-harvested and decimating critical habitat in places like Borneo, Sumatra. Nutritional choices seem to be more than just for personal health, but need to include global health and consequences.

    • Maria

      Reply Reply August 10, 2016

      Natalie, I would always badmouth butter because it’s an animal product and I am vegan.

      Butter is a by product of the endless suffering cows and their babies (who are taken away from them so that we can have milk, cheese and butter) have to endure throughout their lives. I always say a big NO to that :)

  • Jackie Grajales

    Reply Reply September 11, 2014

    I’m confused. I was told that olive oil would be best for sprinkling on cold food and not for cooking. I was using extra strength olive oil to cook all of my food and this nutritionist told me to use coconut oil instead or ghee.

    • Alex

      Reply Reply September 11, 2014

      Jackie – people write on the internet about olive oil releasing oxidation products when heated but there isn’t compelling evidence other than the study I mentioned in my other comment above. Studies have shown oxidation (during cooking) happens to a lesser degree in olive oil than in other vegetable oils. The amount of degradation is so minimal, that we’re just talking about a tiny number of oxidation products, which are hardly a concern. Having said that, I’d agree that coconut oil or ghee are better options for cooking since they have a smaller percentage of polyunsaturated fats :-)

  • Hilary

    Reply Reply September 11, 2014

    Where does rapeseed oil feature in the ratings?
    and
    What do you think of lard as a fat for cooking with?
    and
    I have some linseed oil which may well be rancid by now – is there any way of using this so that it is palatable?
    Look forward to responses!

    • Alex

      Reply Reply September 11, 2014

      Hi Hilary, thanks for your questions! Have a look at the table in our “Oils For Cooking Workbook”, where you can find the percentage of polyunsaturated fats and the smoke point of rapeseed oil, lard and lindseed oil: see the Oils for Cooking Workbook™. Remember, when cooking, we’re looking for a LOW percentage of polyunsaturated fats and a HIGH smoke point. You can definitely make your meals more palatable by adding a fresh oil that you enjoy to a finished dish (after being cooked), in which case you don’t need to worry about oxidation or smoke points, and in fact I’d go for something with healthy omegas (which are polyunsaturated). By the way, let’s throw away that rancid lindseed oil :-)

  • Kit Berry

    Reply Reply September 11, 2014

    So how about cooking with virgin or extra virgin olive oil? Is that okay – apart from being an expensive option.

    • Alex

      Reply Reply September 11, 2014

      Hi Kit! Hopefully some of my answers above would have addressed your question :-) When it comes to cooking, it’s important to check how refined the oil you use is: the least refined, the more unstable under heat. The more unstable, the more free radicals/oxidation you get. By the way, people tend to choose virgin olive oil because of its beneficial compounds (like phenols and other antioxidants), some of which may be lost during the cooking process. But you can compensate that by adding your virgin olive oil to salads or finished dishes :-)

  • LisaMarie Richmire

    Reply Reply September 11, 2014

    What oils are best for baking? And What oils are recommended for salad dressings? Again that are the most heart healthy.

    • Alex

      Reply Reply September 11, 2014

      Hi LisaMarie! I’m glad you asked this, because the context of today’s topic is toxicity, as opposed to heart health :-) Margarines have trans fats, not good for your heart! And if you’re concerned about the saturated fat content in butter, this is a must read for you: https://thehealthsciencesacademy.org/health-tips/saturated-fat-exonerated/

      For salad dressings, flaxseed oil (rich in omega 3) wouldn’t be a bad idea :-)

  • Peggy

    Reply Reply September 11, 2014

    I use Rice Oil

  • Lainey

    Reply Reply September 12, 2014

    Hi there. I thought that olive oil and avacado oils were unsaturated fats and that we were to avoid saturated fats such as the tropical oils. I’m sorry, I’ve read all the comments already.
    Thanks for your help.

  • Bernadette Gilder

    Reply Reply September 12, 2014

    Oh dear! Gonna have to redo my research :0( Why have I got it firmly in my mind that Olive oil is best lightly heated and that rapeseed (canola) and sunflower are best for hard frying? Has opinion/the evidence-base changed?

    • Alex

      Reply Reply September 12, 2014

      Bernardette, there has never been any data to support that, unfortunately you’ll always find things written on the internet that aren’t fully backed by research. Again, when it comes to toxicity in oils for cooking, the evidence found is presented above, so make sure to keep those principles in mind :-)

  • Helen

    Reply Reply September 12, 2014

    I usually put the Canola Oil in cakes and do not use it for frying. I also don’t use it so frequently but do use Olive Oil for frying and mixing with balsamic vinegar for dipping bread and Rapeseed Oil for baked potatoes. I will try Flax Oil for salads and see where I can get hold of some of these other oils that I haven’t seen before such as coconut and avocado (possibly because I’m not looking for them). I think if I use it in moderation and eat lots of broccoli :-) we should be OK.

  • Frank Donnelly

    Reply Reply September 12, 2014

    Have just checked my oil that my wife and I use. We have one that looks very cheap, and extra virgin olive oil which looks a lot darker than the cheap one. Great article thanks. Frank

    • Alex

      Reply Reply September 12, 2014

      Thanks, Frank! I love to hear that you and your wife just checked what you keep in your kitchen, it’s students like you who keep us motivated to do what we do :-)

  • Chris

    Reply Reply September 13, 2014

    Great article Alex. A lot of people are confused by this subject. I have been reading about oils for quite a while and switched over to virgin coconut oil years ago for its many benefits. I mostly use virgin olive oil in my salad dressing and I use butter if I am lightly scrambling an egg. I was also buying lard from the farmers market which (not bleached and refined as the store bought) I believe would be a good alternative for meat eaters to roast or fry with again in moderation.

  • Karen

    Reply Reply September 16, 2014

    This article has reinforced advice given to me by a friend who recommended coconut oil as a healthier alternative to sunflower oil for cooking. I hate the smell of coconut but have to admit when using it to cook with, there has been no difference in taste.

    If you find coconut oil hard to find, try any major ethnic Asian, Caribbean or African store. It has multi-purpose usage in these cultures, for food, hair and skin.

    • Natalie

      Reply Reply September 16, 2014

      Karen, you can find it now in Tesco in the oils section – great stuff!

  • Susan Gisella Barr

    Reply Reply September 26, 2014

    Author of the coconut oil book, is Siegfried Gursche, MH A must have book! It has a wealth of information, miracle oil for heart disease, diabetes, cancer, healthy skin and hair, HIV/AIDS,cleanses liver, and more! A great read!

  • Milena

    Reply Reply October 20, 2014

    This is a very informative article.i ve never tried coconut oil for deep fry.but now ill give it a try.always used sunflower

  • Beverly Velasquez

    Reply Reply November 6, 2014

    Could you tell me where peanut oil falls in the charts? Also is there any alternatives to oils in frying? I know of a few in baking.

  • Claudia

    Reply Reply November 6, 2014

    We have been using coconut oil for all our frying,cooking and baking for years now. I use olive oil only for salad dressing. I use organic butter, as well, when I want that taste. Coconut oil that doesn’t taste like coconut enhances the flavor of food. It is super good for frying and popcorn made with it is soooo good. Coconut oil can also be used for candy and fudge with very little sugar. We don’t really like to go out to eat anymore because we know they use bad oils. I use coconut oil to wash my face and shave my legs and I don’t need a moisturizer or lotion.

  • Maria, Research Analyst (The Health Sciences Academy)

    Reply Reply November 6, 2014

    Hi! I just wanted to let you know that we’ve uploaded our Oils For Cooking Workbook™ (free PDF download) so you can work out if the oils you use for high-heat cooking are suitable (frying, sautéing, grilling, pan roasting, searing, stir-frying, and caramelising). The same criteria is recommended for medium-heat cooking (gentle sauté, stewing, baking, or braising). Remember, the context of this is toxicity, oxidation, release of free radicals (which can cause DNA damage), and degradation of oils for cooking – rather than heart health, or weight loss, or everything else under the sun :) Here’s the link to the Oils for Cooking Workbook™ (Enjoy!)

    Maria (Research Analyst, The Health Sciences Academy)

  • Anna Kudzia

    Reply Reply December 4, 2014

    Rice bran oil is the oil extracted from the hard outer brown layer of rice after chaff ( rice husk). It is notable for its high smoke point of 232 °C (450 °F) and its mild flavor, making it suitable for high-temperature cooking methods such as stir fry;
    It is popular as a cooking oil in several Asian countries, including Japan, India and China.
    Saturated fats
    Total saturated 25% while olive oil has 15% of saturated fats

    http://en.wikipedia.org/wiki/Rice_bran_oil

    Paul, A.; Masih, D., Masih, J., Malik, P. (2012). “COMPARATIVE ANALYSIS OF HEAT DEGRADATION OF ORYZANOL IN RICE BRAN OIL, MUSTARD OIL AND SUNFLOWER OIL BY MICROWAVE AND PAN HEATING”. International Journal of Food and Nutritional Sciences 1 (1): 110–117. Retrieved December 2012.
    that could be interesting to read

    • Maria, Research Analyst (The Health Sciences Academy)

      Reply Reply December 4, 2014

      Hi Anna! Thanks for the very interesting links :) Just bear in mind that although rice bran oil has a high smoke point, it does not fully meet the criteria (see the cover of the Oils For Cooking Workbook), where you should look for LESS than 15% polyunsaturated fats in the oils that you use for high heat cooking (rice bran oil has more than twice that much: 33%). Thanks! Maria (Research Analyst)

  • Rhoda

    Reply Reply February 27, 2015

    Thank you all for the information about cooking oils, where does vegetable oil come into all this, as I thought it was good for cooking. I have learnt a lot about olive oil, I now use it for my salads and I have just started using coconut oil and I just love it as it seems to be good for everything.
    Thank you for the link about the oils.
    Rhoda

    • Maria (Research Analyst)

      Reply Reply February 27, 2015

      Rhoda – glad we could help! When you buy a vegetable oil, check the label to see which oil or combination is being used; you can then work out the suitability on the basis of the Oils For Cooking Workbook :-)

  • Tanja

    Reply Reply March 23, 2015

    What about extra virgin cold pressed rapeseed oil? I have used that for roasting as it has a high smoking point and contains omega 3, 6 a and 9, but now I’m wondering whether I’d be better off using something else?

    • Hi Tanja! If you use rapeseed oil for high-heat cooking, make sure to follow the steps in the workbook to assess suitability. The workbook will also help you to shortlist a few alternatives, which is always handy. Our goal is for you to do the work and to learn exactly how to do this on your own by following the steps, that way you can make your own decisions but in an informed manner. Once you have your shortlist of alternatives, you may want to create a comparison chart (on paper or a spreadsheet) with their individual properties and nutritional values to further narrow things down. Have fun with the process and detective work!

  • Neeta Sanders

    Reply Reply July 31, 2015

    I teach vegan cooking classes and health seminars, and one oil that I advise my students to use and has a high smoke point and was not mentioned in the article is Grapeseed oil. This oil has many beneficial properties:
    • High in vitamin E and omega-6 fatty acids
    • Contains natural antioxidants
    • Has been shown to raise good cholesterol (HDL) and lower bad cholesterol (LDL)

    By the way I love your website and am thoroughly enjoying the course I am currently enrolled in. Thank you for providing a wealth of information!

    • Neeta, thanks so much! Your cooking classes sound fun, and we love to hear you’re enjoying your time with us :-) Grapeseed oil has a high smoke point but the polyunsaturated fats percentage is five times higher than the recommended 15% for high-heat cooking, that’s a lot, meaning that when heated it produces a much larger amount of free radicals and genotoxins when compared to the oils in our recommended list (all with less than 15% polyunsaturated fats and a smoke point above 160 C). High-heat exposure can cancel out the health benefits of many healthy oils (beneficial when not heated, ideally used fresh in finished dishes). For the exact criteria and the full list, have a look at our Oils for Cooking Workbook™ Enjoy!! Maria (THSA team)

  • Kevin Grain

    Reply Reply August 10, 2015

    Canola oil, or rapeseed oil as we call it in the UK, is not one third polyunsaturated fat, it’s around a quarter. Reading directly from the back of Mazola pure rapseed oil, it states 25.1 grams per 100 of polyunsaturated fat. I agree with the article. There is an Internet based myth that rapeseed oil is bad for you. It’s packed with Omega-3 and helps the Omega-3 to Omega-6 balance. Given that, it’s far better than sunflower oil, which is the real problem, being massively high in polyunsaturated fat.

    • Hi Kevin – thanks for commenting. Good to hear you checked the label. Based on the scientific literature, the average is 32% PUFA for canola/rapeseed. Then each brand (independently) reports a different PUFA % based on their own in-house assessments. For example, Farrington’s reports 28% PUFA and 10% Omega 3. That’s still well above the recommended 15% PUFA limit for high-heat cooking, fomenting a higher production of food mutagens than lower PUFA oils. At the end of the day, it’s a personal choice, and the effects may also differ between those who use these daily vs. rarely or once in a while. For higher PUFA oils, your best bet is to use them on finished dishes, either cold or slightly warmed :-) Thanks! Maria (THSA team)

  • georgina

    Reply Reply September 9, 2015

    Thank you for the insight into oils, I now know which oils to use for the appropriate method of cooking, and I hope to be substituting the sunflower and vegetable oil in my next food shop!

  • Jo

    Reply Reply November 24, 2015

    Really interesting article :-) Thank you!
    In my cupboard I have Biona’s organic coconut oil CUISINE – mild and odourless and states can be used for baking, frying and roasting as well as organic extra virgin coconut oil cold pressed. Is one better than the other?
    Also, Rapeseed oil isn’t listed in the workbook and I would love to know more :-)

    • Hi Jo – we love to hear you enjoyed it! To compare coconut oil vs olive oil, you can list their PUFA % and smoke points next to each other and see which one wins :-) And rapeseed oil is in the workbook too, with its alternative name: “canola oil”. So make sure to run a comparison of all three. Enjoy! Maria (THSA team)

  • Barbara

    Reply Reply January 20, 2016

    The information on “Cooking Oils” was informative; however, should these oils be used in baking as well? I have mostly used Canola Oil for baking, and just recently started using Coconut Oil. I assume the measurements would be the same for liquid versus solid oils, is that correct? Thank you!

  • Liz Drummond

    Reply Reply February 2, 2016

    A very useful article, thank you. I’m one of the few people who is sensitive to coconut oil (muscle and joint pain increases and my energy levels plummet), and there’s dairy intolerance in my family, and I get muscle weakness with butter, so I’m guessing that refined olive oil is my option unless you suggest anything else?

  • Zuzana

    Reply Reply March 1, 2016

    Thank you for the article and easy understandable explanation. I am mostly using Olive oil for cooking, but I always buy the extra virgin one, usually not so expensive one, so not really sure about the quality. My concern is, how can I recognise a refined olive oil (without the combustible solids)? Can I find it written anywhere on the bottle? Thank you so much!

  • Joanne Turner

    Reply Reply October 29, 2016

    Hi I have read through the article on oils and the oils workbook but can’t see Rapeseed oil. Is it ok to cook with? Also I’ve heard that coconut oil is bad for you due to saturated fats but also heard it’s good for you as they are a good type of saturated oil could you clarify please?

    Joanne

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