It’s hard not to extol the virtues of extra-virgin olive oil. Unlike most overly processed oils you find at the supermarket that are high in omega-6 polyunsaturated fats, olive oil is one of the best sources of monounsaturated fatty acids, heart-healthy fats that may lower your risk for heart disease. Olive oil is the oil people who live in the Mediterranean region eat and cook with and the most abundant oil in the Mediterranean diet, an eating style linked with longevity.
Despite the fact that extra-virgin olive oil is one of the healthier oils you can use in your diet, if you read online you’ll discover that some people refuse to cook with it, believing the fats in olive are unstable and break down under heat into harmful free-radical compounds that can damage cells. Therefore, they use extra-virgin olive oil at room temperature for salad dressings and other non-cook applications but use another oil for cooking. Is it true that olive oil is unsafe when you heat it?
Stability of Cooking Oils
First, let’s look at what makes an oil unstable and prone to oxidation. The most stable oils are those that are highest in saturated fat. If you look at the chemical structure of saturated fat, it has no double bonds, making it very unreactive and unlikely to oxidize even at high temperatures.
In contrast, polyunsaturated fats have many double bonds. The double bonds in these fats make them less stable and more reactive. The greater number of double bonds increases the likelihood that under the right conditions, such as exposure to high heat, they’ll oxidize. In contrast, monounsaturated fat, the predominant ones in olive oil, contains a single double bond, making them less likely, relative to polyunsaturated fats, to oxidize.
Virgin olive oil has another feature that makes it less likely to form harmful, free radical compounds when heated. It’s a rich source of antioxidants, including polyphenols. What do antioxidants do? They protect against oxidative damage. A study published in Food Chemistry and Toxicology showed olive oil samples that contained more natural polyphenols were more resistant to oxidation when exposed to heat.
Combine this with the fact that the most abundant fat in olive oil is monounsaturated, a type that’s more resistant to oxidation, and you can see that olive oil should hold up under heat better than most commercial cooking oils, like soybean oil, corn oil, and grapeseed oil, which contain an abundance of unstable, polyunsaturated fatty acids.
What does science say? In a study published in the Journal of Agricultural Food Chemistry, researchers heated various extra-virgin olive oils from different sources to just over 350 degrees Fahrenheit for 36 hours. Despite being exposed to high heat for a whopping 3 days, there was only a minor breakdown of the phenols in olive oil and the oil still retained most of its nutritional components. If extra-virgin olive oil can hold up to three days of heat with only minor degradation of polyphenols, it’s not likely it will form significant amounts of harmful compounds when you heat it up during a cooking session.
Choose an Olive Oil High in Polyphenols
As these studies show, the antioxidant polyphenols in olive oil protect against the formation of harmful compounds when you heat olive oil. That’s why your best choice is an olive high in polyphenols. What’s your best bet? Extra-virgin olive oil is the least processed and the riches in polyphenols. Unlike other oils that are exposed to heat, extra-virgin olive oil is cold-pressed without using heat or chemicals. Therefore, it retains more of its antioxidants, like vitamin E, and polyphenols. Extra-virgin olive oil typically has a greenish-gold color and has a rich, fruity flavor.
Virgin olive oil is also cold-pressed, but it’s more acidic than extra-virgin olive oil, giving it a less pleasing flavor. On store shelves, you’ll also see “pure olive oil.” This olive oil is a blend of virgin olive oil and refined olive oil. So, it has significantly less natural antioxidants.
Cooking with Extra-Virgin Olive Oil
Although it’s safe to cook with extra-virgin olive oil, you don’t want to take the temperature beyond its smoke point, which is between 350 degrees Fahrenheit and 400 degrees Fahrenheit. This temperature range makes extra-virgin olive oil suitable for sautéing, baking and roasting. Regular olive oil has a slightly higher smoke point of between 390 degrees Fahrenheit and 450 degrees Fahrenheit.
How you store olive oil matters too. Keep it in a dark, cool place at a temperature of between 65 degrees Fahrenheit and 70 degrees Fahrenheit to prolong its life.
How can you avoid buying “fake” olive oil that comes from the all too common practice of diluting olive oil with other oils? Researchers at the University of California at Davis issued a report on olive oil in 2011. It showed a number of brands of so-called extra-virgin olive did not meet the standards and were either diluted with refined oils, were of poor quality or had been exposed to heat.
The California Olive Council tests olive oils and gives them their seal of approval if they’re legit. One way to avoid fakes is to buy an olive oil with the California Olive Council’s certification seal. To be certified, olive oil has to meet the following criteria:
. It must be extracted without the use of chemicals or excessive heat.
. It must have less than 0.5% oleic acid, the component that gives lower quality olive oils its acidic taste
. It must pass a blind taste test to ensure it tastes like real olive oil
The Bottom Line
Olive oil is one of the healthier cooking oils at your disposal. If you keep it below the smoke point, there’s no evidence that cooking with it is unsafe. Make sure what you’re buying really IS extra-virgin olive oil and not a mixture of olive oil and refined oils.
European Journal of Lipid Science and Technology. Volume 104, Issue 9-10, pages 661-676, October 2002.
Food Chem Toxicol. 2010 Oct;48(10):2972-9. doi: 10.1016/j.fct.2010.07.036. Epub 2010 Aug 3.
J Agric Food Chem. 2007 Nov 14;55(23):9646-54. Epub 2007 Oct 13.
International Olive Council. “The Differences Between Virgin Olive Oil (VOO) and Extra-Virgin Olive Oil (EVOO) and Fine Virgine Olive Oil.
The Olive Oil Experience. “California Olive Oil Council”
Molecules. 2010 Dec 1;15(12):8734-46. doi: 10.3390/molecules15128734.
Report: Evaluation of Extra-Virgin Olive Oil Sold in California. Frankel, E. N.; Mailer, R. J.; Wang, S. C.; Shoemaker, C. F.; Guinard, J.-X.; Flynn, J. D.; Sturzenberger, N. D.
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