Whether you drizzle it on your salad or use it to sauté your veggies, olive oil is a staple in kitchens. And for good reason: Extra-virgin olive oil is a key ingredient in the Mediterranean diet, which expert panelists voted No. 1 on U.S. News’ 2023 Best Diets list. That’s the Mediterranean diet’s sixth consecutive win.
But in recent years, alarms have repeatedly sounded over fears of olive oil’s “smoke point” and how heating olive oil to this temperature could release harmful compounds. Cautious consumers worried that heating olive oil during cooking would, at best, take away from olive oil’s health benefits and, at worst, be dangerous.
However, 2018 research published in Acta Scientific Nutritional Health shows that not only is extra-virgin olive oil safe when cooked at extremely high heat, it is more chemically stable at those temperatures than other common cooking oils.
[See: The Best Diets for Your Heart.]
Benefits of Olive Oil
Fats get a bad rep, but the truth is that your body needs them to function properly. It all depends on the type of fat you’re eating. Saturated fat and trans fat raise your blood cholesterol levels and are linked to cardiovascular disease.
Olive oil is high in monounsaturated fatty acids and unsaturated fat. Unlike saturated fat, these types of fats are shown to improve cholesterol levels, which can — in turn — decrease your risk of heart disease and Type 2 diabetes.
Olive oil is rich in a compound called phenols, or polyphenols, which are a type of antioxidant that’s found in plant matter. As an antioxidant, polyphenols have protective properties by neutralizing free radicals, which can damage your body’s cells and contribute to the development of certain types of health conditions, such as heart disease, dementia and cancer.
Research has linked phenols with:
— Decreased blood pressure.
— Lower levels of chronic inflammation.
— More efficient use of insulin to better store glucose.
— Improved heart health.
The difference between olive oil types comes down to how they are processed. Extra-virgin olive oil results from the first pressing of olives, while regular olive oil is a blend of the first pressing and subsequent processing.
Many food labels state that extra-virgin olive oil is for dressings and finishing, while olive oil is for cooking, since the latter is less expensive and doesn’t have as great of a flavor. But this is not related to smoke points, experts say.
[See: Favorite Mediterranean Diet Recipes From America’s Test Kitchen.]
What Is a Smoke Point?
Essentially, a smoke point is the point your oil stops shimmering in the pan and starts to turn to smoke.
“The smoke point of an oil or fat is the temperature at which, under defined conditions, sufficient volatile compounds emerge from the oil and a bluish smoke becomes clearly visible,” explains agricultural engineer Leandro Ravetti, technical director of Modern Olives laboratory in Australia, who served also served as the co-author of the 2018 Acta Scientific Nutritional Health study. “At this temperature, volatile compounds — such as free-fatty acids, polar compounds and short-chain degradation products — evaporate from the oil.”
Such harmful compounds, including lipid peroxides, may contribute to lung cancer and bladder cancer risk, according to a 2011 Molecular Nutrition & Food Research study. Additionally, a 2019 study conducted at the University of Massachusetts at Amherst found that oxidized frying oil is correlated to inflammatory bowel disease and colon cancer in mice.
Every oil and fat has a unique smoke point, with temperatures ranging from more than 400 degrees Fahrenheit for grapeseed oil to about 300 degrees for butter. According to the North American Olive Oil Association, extra-virgin olive oil’s smoke point is 350 to 410 degrees, and olive oil’s smoke point is 390 to 468 degrees.
[SEE: Cooking at Home on the Mediterranean Diet.]
Oxidative Stability
“Cooking oils, when heated, undergo a process called oxidation, which can produce harmful byproducts,” says Mamud Kara, physician and founder of supplement company KaraMD. “This occurs when an oil breaks down under heat, so the more an oil can resist this oxidation process the better it is for cooking.”
This ability to resist oxidation is referred to as oxidative stability.
In the Acta Scientific Nutritional Health study, 10 of the most commonly used cooking oils were selected from the supermarket and heated in two different trials. In the first, the oils were heated for about 20 minutes until they reached 464 degrees. In the second trial, the oils were heated in a deep fryer to 356 degrees, the highest temperature recommended for deep-frying foods, for six hours.
In both tests, extra-virgin olive oil displayed the greatest oxidative stability, producing lower levels of polar compounds, trans fats and other byproducts when compared with other oils that had higher smoke points.
“Smoke point does not correlate with the timing when the oil starts to break down or lose stability,” explains Selina Wang, department vice chair and associate professor of food science and technology at the University of California, Davis.
While olive oil has a moderate smoke point, its stability may be due to its high levels of antioxidants, as well as monounsaturated fats, she adds.
Extra-virgin olive oil was the most stable oil when heated, while coconut and other virgin oils — such as avocado — followed close behind.
In a 2010 Food and Chemical Toxicology study, when researchers fried various types of olive oil, only after 24 to 27 hours of frying were the oils considered to be harmful. And in a 2015 Food Chemistry study, when researchers deep fried and sautéed potato, tomato, eggplant and pumpkin, antioxidant levels of the foods actually increased, showing that olive oil continues to deliver nutritional benefits even when cooked at a high heat.
“Oxidative stability, not smoke point, is the best predictor of how an oil behaves during cooking,” says Holly Herrington, a registered dietitian at Northwestern Memorial Hospital in Chicago.
Maintaining an Oil’s Stability
When you’re cooking with olive oil, you’re not typically just heating olive oil by itself in a laboratory and serving it straight.
“The smoke point is determined in an enclosed environment, using only a very small volume of oil in a small brass capsule,” Ravetti says.
Certain factors — such as the amount of oil used and the presence of air — can increase the temperature at which a given oil smokes. This means that, in practice, oil smoke points are likely greater than their official numbers.
However, there are other factors that can affect an oil’s stability. One is exposure to light. Over time, natural and artificial lights — like the ones in your kitchen — can degrade olive oil’s quality, and lead to oxidation.
“Make sure you buy olive oils that are in dark-coated containers, tins or bags and store the oil (in a dark space),” Kara recommends.
Another factor is just time itself. We don’t typically think of oils as a type of food with an expiration date, but it definitely has one.
“When unsaturated fats become rancid or oxidized, they lose their benefits and efficacy starts to decline,” Kara says. “Rancid olive oil will typically smell like rotten fruit and taste bitter.”
Cooking at Higher Temperatures
While you may not reach heats high enough to degrade the oil to a chemically dangerous level, cooking foods in a smoking oil can create a burnt or bitter taste. That’s why when deep-drying or searing, some people like to use refined, high-smoke point oils. These tend to be higher in fat, but you do have some healthy options to reach for instead of vegetable or corn oil, like:
— Avocado oil rich in heart-healthy oleic acid, this oil has a high smoke point of 520 degrees and is best for deep-frying, searing and stir-frying.
— Almond oil is filled with essential vitamins, like vitamin E. It has a smoke point of 430 degrees which makes it great if you are looking to fry or sear foods.
— Grapeseed oil is a byproduct of winemaking and is relatively high in vitamin E. Its 400-degree smoke point makes it perfect for sautéing and stir-frying.
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originally appeared on usnews.com
Update 04/06/23: This piece was previously published at an earlier date and has been updated with new information.
