Which Cooking Oil is the Healthiest?
This is a question that I am asked all the time. In many cases, the person asking me this question is someone that has cancer and is undergoing treatment, or they have finished their treatment. That’s important because there are many considerations when choosing a vegetable oil and knowing that cancer risk reduction is a priority will help determine the best answer.
The oils that I use and recommend are extra virgin olive oil, flax oil and organic canola oil. But why? And why not some of the other oils?
Below is everything you wanted to know about vegetable oils designed to help you know whether to stick with your current choices or make a change and help you understand what is on your oil’s label.
What to Consider when Choosing a Vegetable Oil?
In deciding the best way to organize this information, I’ve divided this into the health and non-health attributes. Let’s start with non-health attributes, which include some of the sensory and processing differences.
In some dishes, you may want to flavour of the oil to shine through and provide a distinct flavour note. For example, if you have some beautiful fresh bread and you want to make an oil and vinegar for dipping. In this case, you would want to use a flavourful oil like extra virgin olive oil. Like wine tasting, olive oil, is given flavour attributes based on the sensory qualities. A ‘fruity’ olive oil would have flavours like artichoke, grass and fruits. It can also have pungency like chili’s or black pepper and its third flavour note is bitterness, which comes from unripe olives and can be desired by some – it all depends on your preference. If you are baking some muffins and don’t want a heavy taste to ruin your recipe than you would choose an oil with a very light or neutral taste. In this case, something like canola oil or sunflower oil would be used.
Taste is very closely linked to the level
of refinement. Some oils are naturally neutral tasting such as sunflower oil while others are naturally stronger flavoured such as avocado or coconut oil. But an oil can be refined or filtered. When this is done, the colour and flavour become more neutral and it can be heated to a higher temperature before it burns. The downside is that as well as losing flavour you are also losing some of the beneficial plant compounds from the original fruit or seed source. As well as affecting the taste, there is concern about the refining process, referred to as RBG which stands for refined, bleached, deodorized. Controversy exists about hexane which is one product of RBG processing which could remain in the oil in small levels, but credible sources indicate that these oils are safe (12). While refined oils can still be considered organic (13) and are safe, you may choose to avoid oils made in this way. If you do, then look for terms like ‘cold pressed’, ‘unrefined’ or ‘virgin’ (discussed below)
While many websites that I looked at say this is the ‘most important’ consideration in choosing an oil, I don’t
agree. In fact, I think it’s one of the least important attributes, save for a few recipes in which you really need a high heat. Most of the clients and audience members that I work with tell me that when they cook, they use a medium-low heat. I do the same. There may be one or two special recipes like frying cannoli or homemade spring rolls for which you need a high smoke point oil, otherwise, pay attention to the health attributes of the oil and not to the smoke point. While heating an oil beyond its smoke point and consuming it would certainly not be healthy, heating an oil beyond its smoke point would be obvious by the blue smoke and foul smell. I think all of us have the common sense not to eat a smoky, foul smelling fried food.
Virgin oils are obtained, without altering the nature of the oil, by mechanical procedures, e.g. expelling or pressing, and the application of heat only. They may have been purified by washing with water, settling, filtering and centrifuging only (6).
Oils are obtained, without altering the oil, by mechanical procedures only, e.g. expelling or pressing, without the application of heat. They may have been purified by washing with water, settling, filtering and centrifuging only. No food additives are permitted in virgin
or cold pressed oils (6).
Genetically Modified or Genetically Engineered
This is an area which I find requires clarification of the terms, so let me do that before I begin. Technically, genetically modified can mean that a crop is modified by any means, included traditional plant breeding, whereas genetically engineered means that a novel product has been created by transferring genetic material from one organism to another. Most people tend to use these terms interchangeably and also to say ‘genetically modified’ when they actually mean ‘genetically engineered’ and this can create confusion and misinformation in this area. There are vegetable oils that have been both genetically modified and genetically engineered. To be clear, traditional plant breeding including selection and hybridization are allowed in organic agriculture. Genetic engineering on the other hand, it not (10).
Oil crops that are approved for genetic engineering in Canada and the U.S. include canola, corn, soy and
cottonseed. Canola and soy have been modified to be herbicide tolerant, which means the farmer can spray the entire field with a synthetic weed killer such as glyphosate, 2,4-D and dicamba and it will kill the weeds, but not the crop. Many consumers and advocates have a concern about the remaining residue on these products after they are harvested. Corn and cotton have been modified to contain an insecticide; a gene from the bacteria Bacillus thurengiensis or “Bt” so that it kills common corn and cotton plant predators such as the corn bore and bollworm (11). Many consumers and advocates are concerned about the harmful effect this has on pollinating insects.
Most people who have a heightened concern about their health or the health of the environment choose to avoid oils made from GE crops, which I think is a prudent choice. If you are wanting to avoid this then choose organic canola or soybean oil. I don’t recommend corn oil…for other reasons but if you choose processed corn products like cereals, tortillas or corn meal, then look for organic or GM Free labels. To read more about GM crops, check out a previous Cancer Bites Blog post called “GM-O or GM-No?”
Choosing an oil labelled organic really has two potential benefits. The first and more obvious one is the benefit to the environment. When a crop is grown organically, the farmer uses only allowed inputs and cannot use synthetic chemicals, which have been linked to the creation of dead zones in our waters. The second benefit is to health. In this regard, I see a couple of benefits, one is that organic produce is lower in synthetic chemical residue and the second is that organic crops can be higher in beneficial plant nutrients (phytonutrients). While the Canadian government assures us that GE crops and the chemicals that are applied to them are safe, I know many cancer survivors prefer to err on the side of caution by limiting risk, even unproven potential risks.
There are several health attributes to consider when choosing a vegetable oil, here is my list. All of these are related to the fatty acids that make up the oil. Any vegetable oil is made up of fatty acids, just like any carbohydrate is made up of sugars and any protein is made up of amino acids. Fatty acids are the natural chemical components of oil and there are various ways to classify these oils. Let’s review them.
Saturated versus Unsaturated
To help you remember this, saturated starts with an “s” as does “solid” and saturated fats are solid fats. For example butter, coconut oil and bacon fat are all solid at room temperature. That means that when you take a pound of butter out of the fridge and leave it on your kitchen counter, it doesn’t melt into a puddle, although it does soften it remains a rectangular shape. Just like that bacon fat that is left in the fry pan after you cook your bacon. When you let it sit, while you eat your brunch, you will see that as the fat cools it turns white and solid. This is the reason you don’t pour this down the kitchen sink while it is still hot – because you know that once it gets down there, it will turn solid again and clog your pipes (at least I hope you know that now…so don’t pour this grease down the sink). You also don’t want to consume too many saturated fats, as they will clog your arteries the same way they clog the kitchen pipes. They harden the arteries – this is called atherosclerosis. To keep your arteries soft and flexible and not hard and plaque-filled, then choose oils that are lower in saturated fats (1). Which ones are these? As I mentioned
earlier, butter, coconut oil and bacon contain saturated fats and you should limit these. Other sources of saturated fats are animal fats and tropical oils and examples include cream, cheese, meat fats and palm kernel oil.
Like all of these terms, it refers to the chemistry of the fatty acids chain. A trans fat has
The hydrogens on opposite sides of the carbon (C) chain and a cis fatty acid has the hydrogens (H) on the same side, as in this image
Image Credit: https://sites.google.com/a/aisr.org/mun-ib/biology/molecular-biology/topic-2-3-carbohydrates-and-lipids
While this looks like such a small difference, this change in the location of the hydrogen changes how the fat behaves in our bodies. There are some trans fats that occur naturally such as in milk fat, while others are man made. These are the more detrimental of the two types of trans fats (2).
Man-Made trans fats are made by heating vegetable oil and adding hydrogen gas, the result is that the oil becomes semi-solid, this type of oil is called “partially hydrogenated” (18). This used to be the way that margarine was made. While margarine is 100% vegetable oil, it is semi-solid and spreadable, unlike vegetable oil that is in a bottle, which is completely liquid. The way to turn the liquid oil into a soft solid was to partially hydrogenate it. Unfortunately, trans fats made in this way are very unhealthy and have been shown to have a negative effect on our blood cholesterol levels to the point that as of September 17, 2018 the Canadian government has banned them (17). Also read more about the difference between partially hydrogenated and fully hydrogenated oils here. You should avoid partially hydrogenated oils, but that has gotten pretty easy now that it’s been banned in many countries around the world. But, trans fats can be made in commercial deep fat fryers such as when making French fries and donuts.
Polyunsaturated and Monounsaturated
As I mentioned above, saturated fats are solid fats and unsaturated fats are liquid at room temperature. The term “unsaturated” again, refers to the chemistry of the fatty acid.
If you want to see a visual on this, see below. In the first image the “C” (carbons) have “H” (hydrogens) attached on all sides, in other words, the ‘carbon is saturated with hydrogen’.
In the second image, there is one (mono means one) double bond between two carbons and therefore this carbon chain is not saturated with hydrogen. Because there is only one double bond, this is called “mono-unsaturated” fatty acid.
In the bottom image, there are two double bonds (or places of unsaturation) on the carbon chain (poly means two or more) this is called a poly-unsaturated fatty acid.
Image Credit: Voster Muchenje, PhD Fort Hare University
The image is from research entitled Producing Pork to meet modern consumer demands.
While these small changes in the natural chemical scaffold of these oil components seem trivial, they actually make a difference in how this oil will behave in the body.
Good examples of this include olive oil and avocado oil, which are made up of fatty acids that are predominantly monounsaturated. The monounsaturated fat in olive oil is called oleic acid, and it referred to as a ‘omega-9 fatty acid’ (more on this below). This chemical structure has a positive influence on health and it has been studied for years since the publication of the now famous Seven Countries study. In this study, the diets of people from seven different countries (United States, Italy, Greece, Japan, Finland, the Netherlands and Yugoslavia) were compared to see which country’s population had the lowest rate of heart and blood vessel diseases. The healthiest diet was found to be from the residents of Crete, Greece and that began ongoing interest in the traditional Mediterranean diet, usually shorted to the “Mediterranean diet” and the health benefits of olive oil. I believe the level of omega-9 (oleic acid) is an important consideration in choosing an oil.
These fats are also considered very healthy and choosing oils with a high amount of polyunsaturated fatty acids is a good choice, but there are not all equal, here are some other characteristics of polyunsaturated fatty acids:
Essential Fatty Acids
Included in the polyunsaturated family are the ‘essential’ fatty acids. This means that the body can not make these fatty acids and they must be consumed in the diet. The two essential fatty acids are called linoleic acid (LA) and alpha-linolenic acid (ALA) (also written as with the Greek symbol for the letter alpha as a-linolenic acid). While essential fatty acid deficiency is a theoretical risk, it is quite rare in healthy people. Signs and symptoms include dry, scaly skin, increased risk of infection, and poor wound healing. For best health, you should consume sources of essential fatty acids in your diet and these include flax, canola and walnuts (ALA) and safflower, sunflower and soybean oil (LA) (19).
You do not require a lot of oil to meet your requirements for essential fatty acids. The Institute of Medicine has established Average Intakes (AIs) for alpha-linolenic acid (ALA) and that is 1.1-1.6 grams per day. One tablespoon of flax oil contains 7.26 grams, so less than a teaspoon a day will meet your needs (3). For the essential fatty acid linoleic acid, the Average Intake is set at 11-17 g per day (14-17 g/day for males and 11-12 g/day for adult females) depending on age will meet your requirements (4). But this fatty acid is found in many foods, so you don’t need to use an oil to get your requirements.
Omega-3, Omega-6 (and Omega-9 Fatty Acids)
Of the two essential fatty acids (ALA and LA) there are also known as omega-3 (ALA) and omega-6 (LA). This again, refers to the chemistry of the carbon chain.
Image credit http://milkgenomics.org/article/getting-omega-3-fatty-acids-milk/
A carbon chain has a beginning and an end, an “alpha and an omega”. When you count from the omega end of the chain, the 3rd carbon from the end has a double bond and this is known as an “omega-3”. When the 6th carbon from the omega end has a double bond, this is called an “omega-6”. Same goes for “omega-9” fatty acids.
Omega-3 Fatty Acids
You read a lot about the health benefits of the omega-3 fatty acids and that is because they have been shown to provide you with an improved cholesterol profile and the omega-3 is anti-inflammatory and a supporter of the immune system. Oils that are highest in omega-3 fatty acid are the cold water fishes, canola and flax oil. Chia seeds, flax seeds and walnuts are also good sources (15). I believe that the omega-3 level of the oil is the most important health attribute and this is the reason why I choose the oils that I do.
Omega-6 Fatty Acids
In contrast to omega-3 fats which seem to be all rainbows and sunshine, the Omega-6 fatty acids, are more of an enigma. As I
mentioned above, linoleic acid is an essential fatty acid, so you must consume it for optimal health. But since it has its double bond on the 6th carbon from the omega end of the carbon chain, it has some unique properties that as it turns out, are less desirable. While it is a complex relationship, omega-6 appears to support inflammation in our bodies and more accurately, a high omega-6:omega-3 ratio. Inflammation is an environment that cancer cells like and so, while you can’t avoid omega-6 fatty acids because they are essential, you can limit your intake. For this reason, I recommend that you avoid oils that are high in omega-6 and these include; grapeseed, corn and peanut oil. The recommendation to reduce your intake of omega-6 fatty acids rich oils is also supported a publication in the British Journal of Medicine (16). Having a low omega-6 content is an important health attribute that influences my decisions about which oil to use.
Omega-9 Fatty Acids
Unlike omega-3 and omega-6, the omega-9 fatty acids are not considered essential. But, they are healthy and do result in an improved blood cholesterol level. Olive oil and avocado oil are both high in the omega-9 fatty acids called ‘oleic acid’ (more on that below).
Seed Oil Variants
If you are a gardener, you will know that for every plant there are different varieties. If you want to plant some tomatoes in your garden, for example, there are several types to choose from. The same is true for seed oil crops. This is most important when it comes to sunflower and safflower plants, two important seed oil crops.
High Oleic and High Linoleic
You may have never noticed this when you shop for vegetable oil, but some oils (usually safflower or sunflower) may make a claim about the amount of oleic acid in the oil, such as “mid-oleic” or “high oleic”.
Why Does the Oleic Acid level Matter?
Oleic acid is a mono-unsaturated omega-9 fatty acid. This is the main fatty acid in olive oil and it’s what is responsible for its beneficial health properties; namely that it can help to lower LDL cholesterol (often called the “bad cholesterol”) and raise HDL cholesterol (often called the “good cholesterol”). It’s also contained in pecan, canola and peanut oil among others. You can remember it this way “Oleic” starts with an “O” as does “olive oil” and I find it’s easy to remember that olive oil is a good oil. Choosing the high oleic versions of safflower and sunflower seed oil is a healthy choice. On the flip side of that, let’s consider what is in sunflower and safflower oils, not labelled “high oleic”.
According to the National Sunflower Association here are four distinct oil types produced from the various sunflower plants (7):
1. High Linoleic – the traditional sunflower plant produced this oil. But it is declining in popularity.
2. Mid-Oleic (also called NuSun®) – this is the most popular version of the oil and was developed through traditional plant breeding (this involves combining the pollen (male flower part) and transferring it to the pistil (female flower part) and creating a plant and harvesting the seed until a seed with a higher level of oleic acid was created (8)).
3. High Oleic – also developed through traditional plant breeding and growing in popularity
4. High Stearic/High Oleic (also called Nutrisun™)– This is the newest version
of sunflower and was also developed through traditional plant breeding. The oil from this plant is sought after as a replacement for unhealthy partially hydrogenated vegetable oils (see trans fats above).
The safflower belongs to the same family as the sunflower (9). There are
two main types of safflowers and safflower oil.
1. High Oleic –contains 70% or more oleic acid
2. High Linoleic – contains 70% or more linoleic acid
As I discussed above, while linoleic acid is an essential fatty acid, it is also an omega-6 fatty acid and therefore considered to be less desirable as it can contribute to chronic inflammation in the body. If you are using safflower or sunflower oil therefore, my recommendation is for you to choose one that is labelled “high oleic”.
Fatty Acid Chain Length
Thankfully, this aspect of the chemistry has terminology that is super simple to understand. The chain lengths are classified as short (less than 6 carbons in the chain) medium (6-12 carbons in the chain) and long (more than 12 carbons in the chain). While the length of the chain does affect how the fatty acid is absorbed and transported in the body, for most people this is not a concern.
There are some medical conditions that require medium chain fatty acids (called medium chain triglyceride or MCT oil) and these include; primary intestinal lymphangiectasia (Waldmann’s disease), Chyloperitoneum (lymphatic fluid in the peritoneal cavity), gallbladder disease or removal, gastrectomy (stomach removal), pancreatic insufficiency, small bowel resection (removal), there is also some evidence that MCT oils can be helpful for lymphedema (read more about that in the blog post called Nutrition for Lymphedema. Promoting the health benefits of MCT for everyone (whether you require it or not) is one of the favourite marketing tools for promoters of coconut oil – since it has 64% MCT oil. But the downside to that MCT oil is a very saturated oil which has been shown to increase your cholesterol level (14). So don’t fall for the hype of coconut oil.
I recommend label reading, it’s important to sort out the important from the superfluous information on the label. The most important information on the label, would be the source of the oil, the processing information (virgin, cold pressed, refined), environmental information (organic, GM-free). Other information would make an oil appear healthier but are actually not any more healthy examples are “zero cholesterol”, “Gluten free” and “zero trans fats”, these area claims that all vegetable oils could make.
What Oil Should I Use?
Here are my recommendations on which oil to choose and why
Extra Virgin Olive oil
- This oil has decades of study showing that it is beneficial for heart health and newer research showing it’s benefit as an anti-inflammatory
- Choosing extra virgin will give you a stronger flavoured oil (with a lower smoke point then refined olive oil) but a greater content of beneficial olive nutrients (phytonutrients)
- Olive oil is very high in omega-9 fatty acid
- The highest in omega-3 fatty acid of all of the vegetable oil
- Omega-3 is essential and is a strong anti-inflammatory
- You can’t cook with this oil, though, but can use it for salad dressings, see my favourite salad dressing recipe here
Organic Canola Oil
- Despite all the internet hype around canola oil, I still think it’s a healthy choice
- It’s the third highest in omega-3 fatty acid (after flax and hemp oil – neither of which you can cook with) so, you can think of it as the highest in omega-3 fat that you can cook with
- I recommend organic because it is approved as a ’round-up ready’ crop and non-organic versions may have higher levels of synthetic weed killer
High Oleic Sunflower or Safflower Oil
- These are both more neutral flavoured oils (as compared to extra virgin olive oil) but are also high in omega-9 fatty acid (oleic acid)
- These oils are anti-inflammatory
As a follow-up to this post, I will be posting a “Round-Up” and asking other dietitians, what oil do they use and why and link to their favourite recipe. Stay tuned for that by signing up to receive my monthly email which will include a link to my latest blogs.
References Used Throughout this Post
- National Heart, Lung and Blood Institute. Atherosclerosis.
2. Stender S, Astrup A and Dyerberg J. Ruminant and industrially produced trans fats: health aspects. Food Nutr Res. 2008.; 52.
3. National Institute of Health. Omega-3 Fatty Acids. Fact Sheet for Health Professionals. Last updated Nov 21, 2018. Accessed May 1, 2019.
(4) Engel, P and Yurko-Mauro, K. Essential Fatty Acids. Intake Recommendations. Accessed May 1, 2019, last updated June 30, 2017.
(5) Canadian Food Inspection Agency. Nutrition Labelling Fats and Oils. Modified Fatty Acid Content. (Accessed May 2, 2019, Last updated Jan 15, 2019)
(6) World health organization and the USFDA. Codes Alimentarius International Food Standards. Standard for Named Vegetable Oils. Last updated 2015.
(7) National Sunflower Association. Sunflower oil fatty acid Profile.
(8) Molinar, R. Traditional Plant Breeding versus Genetic Engineering A Primer. Oct 26, 2012. Accessed May 4, 2019.
(9) Agricultural Marketing Resource Center. Safflower. Accessed May 2, 2019, Last updated August 2018
(10) Canadian Organic Growers. What do standards say about genetic modification? Accessed May 3, 2019.
(11) Canadian Biotechnology Action Network. GM crops and foods on the market in Canada. Accessed May 3, 2019
(12) Crosby, Guy. Harvard School of Public Health. As the Expert: Concerns about Canola Oil. Last updated Dec, 2018, Assessed May 3, 2019)
(13) American Natural Processors. What We Do. Accessed May 5, 2019.
(14) Circulation. 2017 Jul 18;136(3):e1-e23. Epub 2017 Jun 15.Dietary Fats and Cardiovascular Disease: A Presidential Advisory From the American Heart Association. Sacks FM, Lichtenstein AH, Wu JHY, et al, American Heart Association.
(15) National Institute of Health. Omega-3 fatty acids. Last updated Nov 21, 2018. Accessed May 10, 2019
(16) DiNicolantonio, J and O’Keefe J. Importance of maintaining a low omega-6/omega-3 ratio for reducing inflammation. Open-heart. 2018;5:e000946.
(17)Health Canada. Prohibiting the Use of Partially Hydrogenated Oils in Foods. Last updated Sept 15, 2017. Accessed May 10, 2019.
(18) Berkley Wellness. Ask the experts: Hydrogenated Oils. Updated Oct 1, 2011. Accessed May 10, 2019
(19) Oregon State University. Essential Fatty Acids. Last update 2014. Accessed May 10, 2019