Olive Oil

Is It Suitable for High-Heat Cooking?

What is olive oil?

Olive oil is an oil extracted from the fruit of the olive tree (Olea europaea) which originated in the Mediterranean regions. It is produced by pressing whole olives and has a very high content of monounsaturated fats (e.g. omega-9 oleic acid). People have been eating olive oil for thousands of years and it is now more popular than ever. 

Types of Olive Oil

In general, there are 3 types of olive oil:

extra virgin olive oil

Extra virgin olive oil is of the highest quality and the most expensive in the olive oil classification. It is made entirely by mechanical means (crushing olives) without industrial refining, i.e. without the use of chemicals and high heat. It has a smoke point of about 160oC and thus, is not suitable to be used for high-heat cooking. It is best to use extra-virgin olive oil for bread dipping, salad dressing and cold dishes. 

virgin olive oil

Virgin olive oil is extracted from olives solely by mechanical means but without chemicals and heat, similar to extra virgin olive oil. Extra virgin olive oil has no defects of aroma or flavour, and some positive flavour of green and ripe olives. It must also meet numerous chemical parameters and sensory standards. Meanwhile, virgin olive oil has slight defects in aroma or flavour and has to meet a lower chemical standards. Hence, it is slightly lower in quality with about 1.5% free acidity and thus, less expensive. It has a higher smoke point of 210oC and works well for frying and sautéing.

refined olive oil

Refined olive oil is olive oil obtained from virgin olive oil through refining process. It is often labeled as “pure olive oil”, “extra light olive oil” or just “olive oil”. Any virgin olive oil that does not qualify for the virgin classification as defined by its acidity level and other factors will be refined to remove undesirable odours and flavours using high temperatures or chemicals. The result is an odourless, colourless and tasteless oil that is typically blended with a small portion of extra virgin or virgin olive oil to provide some flavour, aroma and colour. Since the refining process also removes natural antioxidants from the olive oil, artificial antioxidants need to be added back to give it a reasonable shelf life. Compared to virgin olive oil, refined olive oil has higher smoke point (240oC), which makes it ideal for high-temperature cooking. 

Nutrition facts

Saturated Fat: 14%
Monounsaturated (e.g. omega-9): 75%
Polyunsaturated (e.g. omega-3, omega-6): 11%

  Omega-3: Omega-6 ratio = 1 : 7

Besides tasting better, extra virgin or virgin olive oil has much more nutrients and antioxidants than the refined alternative. 

Benefits

Olive oil, especially extra virgin olive oil is healthful. Among its health benefits are:

Promote healthy brain function

A study shows that a Mediterranean diet supplemented with extra virgin olive oil appears to improve cognition compared to a low-fat diet7.

Improve joint health

Olive oil, along with fish oil reduce joint pain and morning stiffness, and improve hand grip strength in people with rheumatoid arthritis8.

Support antimicrobial activity

Virgin olive oil is effective in eradicating H. pylori, a harmful bacterium that can cause gastric ulcers and gastric cancer9.

Reduce risk of type 2 diabetes

Olive oil has beneficial effects on blood sugar and help prevent diabetes in subjects with high cardiovascular risk6.

Reduce stroke risk

Olive oil is associated with reduced risk of stroke, the second leading cause of death in developed countries. A study shows that those who consumed olive oil were at a much lower risk of stroke compared to those who did not1.

Protect against heart disease

Olive oil helps reduce risk of heart disease2, which is the common cause of death worldwide. It supports healthy heart by lowers blood pressure, hampers oxidation of LDL (bad) cholesterol and improves the lining of blood vessels.

Support healthy blood pressure

Olive oil has been shown to reduce systolic and diastolic blood pressure3,4. Another study shows that the use of extra virgin olive oil helps reduce daily dosage of antihypertensive medications, which may be mediated by polyphenol in the oil5.

The drawbacks 

  • Extra virgin or virgin olive oil may be fake

Did you know that more than two-thirds of typical brands of these oils found in supermarket shelves aren’t what they claimed to be. A bad olive harvest in Europe tend to lead to further manipulation of olive oil which is in the form of adulteration with non-olive oils, such as corn, sunflower, soybean, peanut and canola oils and/or use of damaged or over-ripe olives. This results in compromised quality that does not meet the classification standards of extra virgin or virgin olive oils. When this happens, not only the true health benefits are being robbed, but it also poses safety hazard, particularly to those with allergy to some of the counterfeit oils (such as peanut oil) used in place of olive oil. To make matters worse, many adulterated olive oils are sold under quality brand names and yet, you cannot differentiate a genuine one from a fake based on the taste, smell or appearance.

 

How to find real olive oil?

  • Be skeptical with labels. Don’t simply trust “extra virgin” or “virgin” labels on the bottles. Some low-grade counterfeit oils illegally carry those labels. Besides, stay away from anything labeled with buzzwords such as “premium”, “natural”, “pure”, “made in Italy” or “light”.

 

  • Look for a quality seal, such as

     

 

 

 

 

 

  • Check the country of origin. Australia and Chile received the highest marks from the US International Trade Commission’s report on average quality of extra virgin olive oil. Californian olive oil is also far less adulterated, especially if it carries the COOC Certified Extra Virgin stamp of approval mentioned above.

 

  • Choose olive oil in dark-tinted glass bottle. Olive oil degrades under light and heat. Avoid those sold in a clear bottles, especially a plastic one. At home, store the oil in a cabinet away from the stove. Olive oil starts to go rancid as soon as you open it. Best to go for smaller bottles that you can use up more quickly.

 

  • Find a reputable company and buy small bottles to try.
 
  • Extra virgin olive oil is not suitable for high-heat cooking

Though extra virgin olive oil is quite stable to heat in terms of its fat composition, it is fairly unstable to heat if its polyphenol composition is being considered. When it is heated over a flame at a temperature of 188oC for 5 minutes, 69% of polyphenol is degraded, causing the loss of these phytonutrients from the oils. To minimize the nutrient loss, the best way is to avoid the use of extra virgin olive oil in daily cooking. 

Furthermore, extra virgin olive oil has low smoke point (160oC). With research-based reasons, many people may choose to go ahead with it for cooking. Nevertheless, the moment the oil starts to smoke continuously when heated beyond its smoke point, the fat molecules start to break down at a much faster rate, leading to additional harmful by-products that can cause unwanted health risks. As a general cooking practice, it is recommended to stay below smoke point if the oils are used for cooking.

 

  • Poor source of omega-3 fatty acid

Despite the fact that olive oil is rich in omega-9, non-essential fatty acids that can be produced by the body, it is a very poor source of omega-3, which is essential fatty acids that the body cannot make it. Modern diets are generally low in omega-3s. To get sufficient omega-3s, you have to drink almost half a bottle (207ml) of olive oil. This amount of oil is equivalent to 1,800 calories, which can easily lead to weight gain and obesity. To harness the health benefits of omega-3s, you may opt for other oils, such as flaxseed oil and camelina oil that are high in omega-3s. 

References:

1. Br J Nutr.2014 Jul 28;112(2):248-59.

2. Pharmacol Res. 2007 Mar;55(3):175-86.

3. Am J Clin Nutr.2004 Oct;80(4):1012-8.

4. Clin Nutr.2004 Oct;23(5):1113-21.

5. Arch Intern Med.2000 Mar 27;160(6):837-42.

6. Diabetes Care.2011 Jan;34(1):14-9.

7. J Neurol Neurosurg Psychiatry.2013 Dec;84(12):1318-25.

8. Nutrition.2005 Feb;21(2):131-6.

9. Helicobacter.2012 Aug;17(4):305-11.