Which cooking oil is best?
This is one of the most hotly debated topics in nutrition.
To answer it accurately we must not only consider if the oil is healthy for you, but if it remains healthy when exposed to high heat.
This article examines the factors that influence how an oil reacts at high temperatures, and reveals what is truly the best oil for cooking.
Oxidative Stability Is The Major Factor, Not Smoke Point
Cooking at high temperatures for extended periods can cause oils to oxidise faster and go bad (rancid).
An oxidised oil means it has reacted with oxygen to produce harmful compounds and toxic by-products. For example, oxidation is one of the reasons you shouldn’t continually reuse the same oil for deep-frying.
The more an oil can resist reacting with oxygen and breaking down, the better for cooking. This quality is measured as oxidative stability and is considered by many oil experts as the best predictor of how an oil reacts during cooking (1, 2, 3).
Smoke Point Is Actually A Poor Measurement
Smoke point refers to the temperature at which an oil produces a thin, continuous stream of bluish smoke.
When an oil breaks down under heat, the flavour of the oil shifts, and toxic by-products such as aldehydes and lipid peroxides are produced (4, 5).
Contrary to what you’ve likely heard, new research indicates that an oil’s smoke point is actually a poor indicator of how stable it is at high heat and how likely it is to break down and form harmful compounds. There are several reasons why (6, 7, 8):
- The current methods used to determine smoke point are limited to an enclosed environment with a very small volume of oil. Under normal cooking conditions oils can reach much higher temperatures than their documented smoke point.
- In saying that, smoke point is not a consistent value throughout the cooking process. The true smoke point can decrease as the oil is heated, especially in seed oils with a high amount of polyunsaturated fats such as canola oil and sunflower oil.
- Most refined oils have a higher smoke point because the refining process removes minor components in order to make them suitable for human consumption. However, they also have significantly higher levels of harmful by-products of oxidation including alcohols, aldehydes and acids.
For these reasons (and many more), emphasis should be placed on oxidative stability rather than smoke point when choosing a cooking oil.
- Key Message: The ability for an oil to resist oxidation and maintain its quality is called oxidative stability. This is the best predictor of how an oil will react when cooking at high heat. Contrary to popular belief, the smoke point is actually a poor measurement.
What Influences Oxidative Stability of an Oil?
There are three major factors that determine an oil’s stability.
1. Number of Antioxidants
Antioxidants are beneficial compounds that we need to survive, and our diet is an essential source of them.
As the name suggests, antioxidants protect against oxidation, which is the undesirable process that occurs quicker when an oil is exposed to high heat for extended periods.
Therefore, antioxidants play a key role in an oils oxidative stability and health benefits. It’s important to consider which oils contain and retain their naturally high antioxidant levels.
2. Type and Ratio of Fats
It’s widely known that the type of fats in an oil determines its healthfulness.
However, it’s also a major factor in determining its stability at high heat.
Specifically, a fat is more resistant to heat if it contains fewer double bonds between its molecules. Double bonds oxidise and break down easier when exposed to heat.
- Saturated fats (SFA): These do not contain any double bonds, which makes them very stable at high temperatures. In fact, this makes oils high in saturated fat solid at room temperature, such as coconut oil.
- Monounsaturated fats (MUFA): These contain only one double bond but are also stable at high temperatures. Olive oil is the richest MUFA oil.
- Polyunsaturated fats (PUFA): These have two or more double bonds, which makes them prone to oxidising at high temperatures and forming harmful by products (9). Common PUFA oils include canola, sesame and sunflower oil.
Oils that are predominantly saturated fat and/or monounsaturated fat are typically the most stable for high heat cooking, with polyunsaturated fats the poorer choice.
3. Processing and Production: Natural or Refined?
Oils have various grades or classifications.
These refer to the methods by which the oil was extracted and bottled. As you might expect, the grade of an oil greatly influences its health properties and suitability for cooking.
- Natural production: This usually involves mechanical methods that require little or no heat to extract the oil from the plant. An example of this is Extra Virgin Olive Oil, which is typically mechanically pressed. As a result, Extra Virgin Olive Oil retains its flavours and naturally high antioxidant levels from the olive fruit.
- Refined production: This method usually involves high heat, high pressure and/or chemicals to bleach, deodorise and neutralise the oils in order to be suitable for consumption. This process strips away natural antioxidants and makes refined oils much more susceptible to the undesirable chemical alterations that cooking initiates. An example of refined oils includes canola oil, sunflower oil and olive oil.
- Key Message: The three main factors that influence an oils oxidative stability are the level of naturally occurring antioxidants, the type of fats it contains, and the method of processing and production.
Comparing Fat Content, Oxidative Stability and Antioxidants of Oils
Here is a list of the average fat ratios, oxidative stability and antioxidant content of common oils (10, 11):
Preliminary results from the Evaluation of chemical and physical changes in different commercial oils during heating. Authors: De Alzaa, F; Guillaume, C.; and Ravetti, L; Modern Olives (2017). Analysis performed by ISO 17025, NATA and AOCS accredited laboratory
*Oxidative stability is measured via induction time. This is the point when an oil breaks down and potentially produces harmful compounds. A greater induction time indicates an oil is more resistant to oxidation, a shorter induction time means the oil will oxidise easily.
From this data we can see that coconut oil has the best oxidative stability, but this is largely due to its saturated fat content. It actually ranks the worst for antioxidant content, with Extra Virgin Olive Oil the best.
All the vegetable oils – which are refined and typically high in PUFA – have a low oxidative stability and low antioxidant content compared with the olive oil varieties. Olives are a fruit and contain naturally high levels of antioxidants. Extra Virgin Olive Oil contains high levels of these natural antioxidants, as they infuse into the oil during the pressing of the fruit.
Known Health Effects of Each Fat
If you consume an oil regularly, the health effects of its fats are important.
This is the final factor to consider when choosing the best oil for cooking.
Saturated Fats and Polyunsaturated Fat
Despite a bad reputation for decades, some researchers argue that saturated fat is neutral for health.
That is, it certainly doesn’t have health benefits, but may not be harmful for the average healthy person (12, 13, 14).
Despite this emerging idea, a number of large reviews studies and analyses show that replacing saturated fat in your diet with polyunsaturated fat (PUFA) reduces the risk of heart disease (15 ,16, 17).
This suggests that the addition of PUFA in the diet – such as omega-3 and omega-6 fats – is beneficial for health, particularly if it replaces saturated fat (which has no benefit to health).
However, the caveat is that PUFA should be consumed from fresh whole foods such as fish and nuts, rather than vegetable oils. As we have established, oils rich in PUFA have very few antioxidants and are very susceptible to oxidation when heated (18).
This leaves us with monounsaturated fat (MUFA), which makes up approximately 75% of the fat found in Extra Virgin Olive Oil and is a staple of the heart-healthy Mediterranean diet.
Studies consistently link a diet high in MUFA with beneficial effects on blood pressure, cholesterol levels, blood glucose levels and other strong markers of metabolic health (19, 20).
In fact, a large review that looked at 32 previous MUFA studies found that when compared to those who ate the least olive oil, those who ate the most olive oil were (21):
- 9% less likely to have a heart problem
- 17% less likely to have a stroke
- and 11% less likely to die early.
As you might expect, replacing saturated fat in the diet with MUFA also appears to be beneficial on markers of metabolic health, much like with PUFA (22).
The difference of course is that unlike all oils rich in PUFA, one of the oils rich in MUFA – Extra Virgin Olive Oil – is high in antioxidants. This means both whole foods rich in MUFA and Extra Virgin Olive Oil are a good source of antioxidants. These antioxidants appear to protect against heart disease and cell damage that contributes to the ageing process (23, 24).
Based on the weight of evidence, it’s clear that the addition of MUFA or PUFA to the diet is beneficial for health overall. However, the benefits of PUFA come from eating whole foods rather than vegetable oils, which are heavily refined and low in antioxidants.
On the other hand, oil rich in MUFA and antioxidants – Extra Virgin Olive Oil – maintains its health-promoting properties when exposed to high heat.
- Key Message: You must consider the known health effects of an oil’s fats if you use it regularly. Saturated fat has no benefits, while polyunsaturated fat in the form of oil will readily oxidise especially after cooking. Monounsaturated fat appears to benefit heart health and maintains much of its health properties after cooking, as long as the oil is high in antioxidants.
Verdict: Extra Virgin Olive Oil Is The Best Choice For Cooking
Extra Virgin Olive Oil is the best oil for cooking when you consider the major factors:
- Oxidative stability: It’s naturally rich in antioxidants, such as vitamin E and phenolic compounds. These nutrients not only increase its health properties but also improve Extra Virgin Olive Oil’s resistance to oxidative damage. For example, Extra Virgin Olive Oil was able to withstand up to 27 straight hours of deep-frying vs only 15 hours for a commercial vegetable oil blend (25).
- Known health effects of monounsaturated fat: As explained above, studies consistently show that those who consume the most olive oil are at a reduced risk of future metabolic health problems. In fact, Extra Virgin Olive Oil is one of the staple foods of the heart-healthy Mediterranean diet.
- Quality of extra virgin: This is the highest grade of olive oil, rich in natural antioxidants to keep it stable at high heat and free of harmful trans fats. It also contains oleocanthal, a unique and powerful antioxidant that is only found in Extra Virgin Olive Oil.
As you can see, this is what makes Extra Virgin Olive Oil the most suitable choice for all conventional cooking methods. This includes stir-frying, pan frying (sauté), deep frying, oven baking and BBQs.
Additionally, its available in a wide range of flavours that can complement both sweet and savoury dishes.
What About Coconut Oil?
Many sources incorrectly claim that coconut oil is the best choice for cooking.
It’s approximately 92% saturated fat, which does make it very stable when exposed to high heat. However, as mentioned earlier, it’s clear that consuming more saturated fat has no benefit to health, whereas consuming more monounsaturated fat does.
Additionally, a recent review study of coconut oil intake and cardiovascular health found that regular consumption was consistently linked with higher total and LDL “bad” cholesterol levels, which is widely considered unideal for heart health (26).
Fats and oils with neutral health effects will simply add excess calories to the diet. Choosing an oil that contains healthy fats, is rich in antioxidants and fat soluble vitamins will instead increase the overall healthfulness of your diet.
Extra Virgin Olive Oil ticks all of these boxes and performs equally as well as coconut oil at high temperatures. In fact, you should only use coconut oil if you’re cooking a dish that benefits from the strong coconut flavour.
- Key Message: Coconut oil is stable for cooking at high temperatures, but it doesn’t outperform Extra Virgin Olive Oil. It contains only trace amounts of antioxidants and is predominantly saturated fat.
Choose Australian Certified Extra Virgin Olive Oil
Not all olive oil is created equal.
In Australia, it’s important to choose locally sourced, Australian certified Extra Virgin Olive Oil. This ensure it is fresher and superior in quality than other oils.
This is largely due to the low amount of free fatty acids and high concentration of antioxidants that results from fresh, healthy olive fruit that is handled and pressed with care.
Not only is a high quality Australian certified Extra Virgin Olive Oil the best choice for cooking, it maintains its quality much longer on the shelf too.
To ensure you are choosing a truly high quality Extra Virgin Olive Oil, look for this Australian triangle certification symbol on the label.