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A dietitian’s deep dive into common cooking oils. Keep reading to learn how oils are processed, which oils are the healthiest, which oils are best to use for different types of cooking, how to store them, and more!
After running a blog reader survey recently, I was shocked to see so many questions on cooking oils! As a dietitian, I’m super excited to break down this topic and to help you choose the best cooking oil for whatever you’re cooking.
If there’s anything I’ve missed, be sure to submit your questions in the comments below.
Some topics we’ll cover in this post:
- Why we don’t need to shy away from using oils in our cooking (i.e. why fats are important in our diets!)
- Which oils are the healthiest
- How oils are processed (extracted + refined)
- What the smoke point is
- Which oils to use for specific types of cooking
- How to properly store cooking oils
- My personal favourite oils to use
Let’s get started!
Why Fats Are Important For Our Health
I wanted to begin this discussion by first addressing a common misconception that oils/fats are “bad” or “fattening.” I’m sure you’ve seen labels or claims about “oil-free” cooking or “fat-free” products. This approach to nutrition is completely antiquated and we do NOT have to fear all oils and fats. In fact, they SHOULD be included in our diets and in our meals.
Why? Because fats (which oils are) have many highly important roles in our body, which are outlined below.
- Fat is essential for the growth and development of our brains, hormones, and all cells throughout our bodies.
- Fat is necessary to absorb fat-soluble vitamins (A, D, E, and K) as well as other beneficial fat-soluble compounds from our food. If you’re not pairing your food with a source of fat, it’s going to be difficult for your body to absorb these other nutrients.
- Fats provide the structural components of our body’s cells. They are necessary to form the membrane that surrounds each cell, which controls the movement of substances in and out of the cells.
- Essential fatty acids (linolenic acid, a omega-6 fatty acid + alpha linolenic acid, an omega-3 fatty acid) are involved in vital functions in the body, such as blood clotting, wound healing, and inflammation.
- Fat provides an insulating layer of protection to our bodies and internal organs.
- Fat helps you maintain your core body temperature, keeping you warm.
- Fat provides a source of energy for our bodies, helping to keep our necessary bodily functions running smoothly.
- Fats digest slower than carbohydrates, meaning they help keep you feeling full and satisfied for longer.
- Fats provide a smooth mouthfeel to our foods, which helps improve flavour and texture, making our meals more satisfying!
In order to support these many important functions, it’s essential that you consume sources of fat on a daily basis. While there are many foods that provide healthy fat (like nuts, seeds, avocados, and fish), cooking oils are often a major source of fats in our diets.
That said, there are specific types of fat that are more beneficial and protective to our bodies. These include both monounsaturated and polyunsaturated (omega-6 + omega-3) fatty acids.
Which Cooking Oils Are The Healthiest?
Olive oil is likely the most well-known and well-researched oil with proven health benefits (I, II). It’s high in heart-healthy monounsaturated fatty acids, which has been shown to reduce the risk of coronary heart disease. It also contains antioxidants and is a good source of vitamin E.
Avocado Oil is also high in heart-healthy monounsaturated fatty acids, antioxidants, and other beneficial plant compounds. It has a neutral flavour and a very high smoke point, making it incredibly versatile for all types of cooking.
Walnut, flax, chia, and hemp seed oils are excellent sources of anti-inflammatory omega-3 fatty acids. These are delicate oils that are best used as finishing oils or in dressings/sauces. Keep them in the refrigerator to extend their shelf life.
Peanut oil is a good source of monounsaturated fatty acids and contains heart-healthy phytosterols (plant compounds that help excrete cholesterol from the body). It’s great for both high heat cooking and also in salad dressings or sauces.
Coconut Oil is a controversial one – some individuals claim it’s a “superfood” while others say it should be avoided at all costs. While coconut oil is high in saturated fats (92%) which has been shown to elevate LDL (bad) cholesterol, it does also appear to be associated with elevated HDL (good) cholesterol levels, too.
That said, the majority of the evidence in support of coconut oil’s beneficial effects on heart health is taken from observational studies. The small amount of clinical trials on this topic have not found a positive effect on heart health (I).
The observational studies that find a positive association between coconut oil consumption and heart health have looked at populations in Southeast Asia who traditionally consume substantial amounts of coconut flesh and oil, but who also include more fresh fruits, vegetables, and fish than the standard Western diet.
Adding coconut oil to a diet of processed foods is unlikely to have a beneficial effect. Remember, it’s our dietary pattern AS A WHOLE that matters more than any one individual food.
Furthermore, the majority of coconut oil’s “health claims” are due to the fact that it contains medium-chain triglycerides (MCTs), which are absorbed differently than long-chain fats. That said, coconut oil is mostly composed of lauric acid, which is metabolized more like other long-chain fatty acids. Thus, the research on 100% MCT oils cannot be directly applied to commercial coconut oils (I). At this point, there is more conclusive research to support using more unsaturated oils, like olive oil.
Bottom line? Using some coconut oil in your cooking is just fine and it can add an incredible flavour to your foods! We probably don’t need to be need to be eating it by the spoonfuls, though (it’s NOT a miracle food).
Vegetable Oils, like canola, sunflower, and safflower. These oils are relatively high in unsaturated fatty acids and have a high smoke point. One thing to note is that these vegetable oils are often highly refined, although high quality, unrefined versions are available. We’ll cover more on what that refining process looks like next!
How Are Cooking Oils Processed?
Cooking oils are derived from a variety of different seeds, fruits, and nuts. The oil is extracted from these different plant sources and sometimes go through more refining processes after that.
Curious what some words on an oil’s label mean? Let’s take a look at some of these methods!
How Are Cooking Oils Extracted?
The removal of oils from their plants (extraction) can be done in 3 different ways:
- Cold-pressing: the mechanical pressing of seeds, plant tissue, or nuts to express the oil without heat. Cold-pressed oils are often of high quality, unrefined, and impart the full flavour of the plants from which they are squeezed.
- Expeller-pressing: the squeezing of the seeds, plant tissue, or nuts at very high pressures, which generates heat.
- Chemical solvents: the chemical removal of the oil from the seeds with solvents. The majority of inexpensive commercial vegetable oils are extracted using chemical solvents. Unless you see “cold-pressed” or “expeller-pressed” on the label, it’s likely that the oil has been extracted with solvents.
How Are Cooking Oils Refined?
Once a cooking oil has been extracted, it is either left unrefined or it gets refined (purified) into a neutral-flavoured oil. An unrefined oil is typically labeled as “virgin.”
Why are some oils refined? An extracted oil can contain naturally-occurring substances like water, resins, gums, colour compounds, soil, and free fatty acids. If these are not removed from the oil, they can affect the flavour, colour, clarity, smoke point, and shelf life of an oil.
Unrefined cooking oils are often more flavourful and thus are great in salad dressings, sauces, etc. They have slightly higher nutritional value than refined oils, but they often have a lower smoke point and a shorter shelf life as they are more prone to rancidity.
Refined cooking oils, on the other hand, often have a very neutral flavour, higher smoke point, and longer shelf life. This is why these oils are more typically used in commercial cooking and food production. The refining process involves 5 steps: degumming, neutralizing, washing/drying, bleaching, and deodorizing.
What Is An Oil’s Smoke Point?
The smoke point is the temperature at which an oil begins to emit some traces of smoke, indicating that the oil is starting to degrade. Below are the smoke points of some common oils, from the highest smoke point to the lowest.
- Avocado oil: 520°F (271°C)
- Safflower oil: 513°F (267°C)
- Canola oil: 470°F (243°C)
- Palm oil: 455°F (235°C)
- Peanut oil: 453°F (234°C)
- Sunflower oil: 450°F (232°C)
- Sesame seed oil: 410°F (210°C)
- Grapeseed oil: 420°F (216°C)
- Olive oil: 375°F (191°C)
- Coconut oil: 350°F (176°C)
- Flax oil: 225°F (107°C)
What Happens When Oils Are Heated Too High?
When an oil is heated to a temperature higher than it’s smoke point, it will start to break down into it’s glycerol and individual fatty acid components. That glycerol molecule will further start to break down into an offensive-smelling smoke called acrolein, which can be an irritant to our respiratory tracts.
In addition to this unpleasant odour, heating an oil too high can alter the taste of the oil (and therefore your food) and compromise the nutritional value of the oil.
Which Oils Should You Use For High-Heat Cooking?
High heat cooking methods (like searing or browning) calls for oils that can withstand a heat of approximately 450°F. Many refined vegetable oils like canola, safflower, or sunflower oils are designed to withstand these high heats.
My personal favourite oil for high-heat cooking is avocado oil. It has a smoke point of 520°F, a neutral flavour, and is high in healthy monounsaturated fatty acids.
Which Oils To Use For Medium-Heat Cooking?
For medium-heat cooking methods (like baking, stir-frying, sautéing, etc.), you can use any of the oils listed in the high-heat cooking section. Normal frying temperatures are around 300°F-375°F.
In addition, olive oil can be used in moderate temperatures (e.g. under 375°F), so it will work fine for lightly sautéing or roasting vegetables.
Peanut oil is great for medium-high heat cooking, but it will transfer a more “nutty” or “earthy” flavour to your food.
Coconut oil, with a smoke point of 350°F can also be used for medium-heat cooking. Do note that coconut oil will impart a coconut-y flavour, which tastes great with some foods! It’s also a good swap for butter and can be used in sweets and baked goods.
No Heat Oils
Certain oils are best not to heat and should be enjoyed as is for their delicious flavours and nutrition benefits. These no-heat oils include ones like walnut, flaxseed, chia seed, and hempseed oil. Use them as finishing oils drizzled over veggies or proteins, or in sauces, dressings, and marinades.
While it can withstand some heat, extra virgin olive oil is a much-loved no-heat oil as well. It imparts a delicious flavour to so many foods!
How To Store Cooking Oils
Cooking oils are subject to a process called oxidative rancidity, or the chemical deterioration of a fat cause by the uptake of oxygen. This can lead to the development of off flavours and odours, as well as the formation of free radicals. The longer an oil is stored, the more likely it is to become rancid.
Oxidative rancidity is facilitated by the presence of light and/or warm temperatures. In order to prevent this degradation of cooking oils, it’s recommended to store your oils in a cool, dark place or in the fridge. Be sure to close oil containers and bottles tightly to avoid additional exposure to oxygen.
If you know you’ll be using an oil frequently, feel free to buy larger bottles of said oils. For me, this means I usually stock up on large, Costco-sized bottles of avocado and olive oil. For less frequently used oils, it’s best to stick with smaller bottles so that they don’t go to waste. If an oil is smelling off, it’s time to toss it!
There are many cooking oils available and the right oil to choose is often dependent on what you’re cooking! Things to consider when choosing a cooking oil:
- Flavour – do you want the oil to add a distinct flavour to your dish? Or do you want to use a more neutral oil that does not affect the flavour of your food?
- Smoke point – will you be cooking your food in high or medium heat? Or are you using this oil in a dressing or sauce?
- Nutrition profile – when possible, select oils that are unrefined and higher in heart-healthy unsaturated fatty acids or omega-3s. Remember that the oil you choose should be kept within it’s intended cooking temperature to maintain its nutrition profile.
This dietitian’s favourite oils?
- I go through olive oil faster than I want to admit – it’s my go-to for salad dressings, drizzling over veggies or proteins, and for roasting vegetables.
- I also LOVE avocado oil for higher heat frying or searing, and it also makes an excellent substitute for any neutral vegetable oil (even in baking).
- I love toasted sesame oil to impart extra flavour to stir-fries or Asian-inspired dishes.
- I’ll use a little bit of coconut oil to sauté fruits like bananas or apples to add to oatmeal, or in place of butter in some recipes.
Do you have any more questions about cooking oils? Let me know in the comments below! I so hope you found this article helpful. For more simple, healthy recipe ideas and nutrition tips, be sure to follow along on Instagram and Pinterest.
Brown, Amy. Understanding Food Principles and Preparation. Stamford, CT. Cengage Learning. 2015.
McWilliams, Margaret. Foods Experimental Perspectives. Upper Saddle River, New Jersey. Pearson Education. 2012.
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This post may contain affiliate links. Please see my disclosure policy