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So which cooking oil is actually best?
To evaluate cooking oils, consider their overall health benefits, flavor and environmental impact, said Selina Wang, a leading expert on edible oils and an associate food science professor at the University of California at Davis. Budget, of course, also can play a role.
Wang said avocado oil, fermented oil and high-oleic vegetable oils are all excellent choices for use at home in your kitchen. But her go-to is extra-virgin olive oil.
"I pretty much use extra-virgin olive oil for everything," she added. "It's really because of health and flavor, but also for the environment."
Here's why extra-virgin olive oil is the best choice, and how other cooking oils stack up.
• 1. Olive oil
In general, extra-virgin olive oil has the most scientific evidence for its health benefits. In a large clinical trial, scientists found that assigning people to eat a Mediterranean diet supplemented with extra-virgin olive oil or nuts lowered their risk of heart attacks and strokes. Other studies have found that diets rich in extra-virgin olive oil can lower your blood pressure, reduce inflammation and decrease your risk of developing Type 2 diabetes or dying from dementia.
That's because olive oil is primarily composed of oleic acid, a monounsaturated fat that's known to protect cardiovascular health. Oils that are high in monounsaturated fat are less likely to raise your cholesterol levels and cardiovascular risk compared to ingredients that are high in saturated fat, such as coconut oil, butter, lard, ghee and palm oil.
Some people are convinced that olive oil shouldn't be used for cooking or frying because it supposedly has a low smoke point. But Wang said that smoke point doesn't tell you much about how stable an oil is or how many harmful by-products are produced when it's heated.
Some people are convinced that olive oil shouldn't be used for cooking or frying because it supposedly has a low smoke point. But Wang said that smoke point doesn't tell you much about how stable an oil is or how many harmful by-products are produced when it's heated.
"If people understood how smoke point tests are done, they wouldn't put that much weight on it," she said. "You literally just heat the oil up and then look to see when it starts to smoke. It's amazing how much weight we put on such a crude and unreliable method."
In one study, scientists heated extra-virgin olive oil and nine other popular cooking oils in a pan fryer and deep fryer to see how they performed under high temperatures. The researchers found that extra-virgin olive oil produced the lowest levels of potentially harmful by-products because the monounsaturated fats and antioxidants it contained "allowed the oil to remain stable when heated."
The authors concluded that an oil's smoke point doesn't tell you the extent to which an oil will degrade or produce harmful by-products when heated.
"People should not believe that smoke point is an indicator of an oil's health benefits or what it's doing in your body," said Wang, who was not involved in the study.
Taste preferences are very subjective. But if you're baking or cooking, then you might want to use an oil that has a mild flavor. In that case, refined olive oil might be a good option because it is high in monounsaturated fats but has little flavor compared to its extra-virgin counterpart.
Olive oil also has a relatively low carbon footprint compared to other oils, Wang said.
• 2. Avocado oil
Another oil that is similarly high in oleic acid, the monounsaturated fat, is extra-virgin avocado oil - another healthy choice for cooking, though it's less studied than extra-virgin olive oil.
"The science is pretty clear that high-oleic oils are the way to go," Wang said. "A simple way to think about it is that oleic acid is the fatty acid that makes olive oil and avocado oils healthy and more resistant to heat. That's why they're good cooking oils."
Like extra-virgin olive oil, extra-virgin avocado oil is also naturally high in vitamin E and other antioxidants that slow the oxidation process, which makes the oils less likely to degrade under high temperatures, Wang said. Avocado oil is versatile and tastes great in salad dressings, marinades or drizzled over a variety of foods. But if the flavor is too strong, try refined avocado oil.
Wang said refined avocado oil is an "upcycled" product that's made from bruised and damaged avocados that would otherwise go to waste because they can't be sold in the fresh produce section in stores. So it gets points for sustainability, too.
Keep in mind, though, that extra-virgin olive and avocado oils are less processed than refined versions of these oils and contain more vitamins and antioxidants.
• 3. Seed oils
Vegetable oils extracted from the seeds of various plants include sunflower, safflower, soybean, canola and corn oil. These so-called seed oils tend to be high in polyunsaturated fats such as linoleic acid.
Many studies have found that polyunsaturated fats are good for cardiovascular health. But polyunsaturated fats aren't as good for cooking at high heat compared to avocado and olive oils. In the study that looked at heated oils, canola oil and other oils with high levels of polyunsaturated fats fared the worst, degrading more readily.
"Monounsaturated fats compared to polyunsaturated fats are more heat stable," Wang said. "That's one of the arguments against seed oils. Some seed oils have a high ratio of polyunsaturated fats, which makes them less stable under heat."
Seed oils have been vilified on social media because they contain high levels of omega-6 fatty acids, which people claim are pro-inflammatory. Some wellness influencers even refer to corn, soybean, sunflower, safflower, cottonseed and other seed oils as the "Hateful Eight," claiming that they are toxic.
The reality is that omega-6s are essential nutrients that our bodies need but can't produce, so it's important that we get them from our diets, said Frank M. Sacks, an emeritus professor of cardiovascular disease prevention and medicine at the Harvard T.H. Chan School of Public Health.
Sacks, who has led several landmark clinical trials on diet and cardiovascular health, said omega-6 fats play an important role in preventing heart disease.
"Omega-6 polyunsaturated fats are very beneficial and should be encouraged for use in a healthful diet," he added. "I use corn oil all the time. That's generally what we use in my house. But we also love extra-virgin olive oil. It depends on your preference."
If cost is a concern, then seed oils can be an affordable alternative to avocado and olive oils.
Wang at U.C. Davis recommends buying seed oils that say "high-oleic" on the label, such as high-oleic sunflower, safflower and canola oils. These are higher in oleic acid - the primary monounsaturated fat in olive and avocado oils - than their regular counterparts.
• 4. Fermented oil
One oil that's better for the environment than a lot of other vegetable oils is something you've probably never heard of: fermented oil.
It's made through the age-old culinary process of fermentation, which is how bread, wine, beer, cheese, yogurt, kombucha and sauerkraut are made. Essentially, a starter-culture of bacteria or yeast is added to food, and the microbes convert or "ferment" the sugars in the food into alcohol, carbon dioxide and other by-products. Only in this case, the microbes convert the sugars into oil.
One of the most popular fermented cooking oils is made by a brand called Zero Acre. It's produced from sugar cane plants that are harvested in South America and then fermented in tanks. The resulting oil is exceptionally high in monounsaturated fat and has a high smoke point and a neutral flavor.
According to Zero Acre, the production of their fermented oil emits fewer greenhouse gases and uses significantly less land and water than the production of other popular vegetable oils. But Zero Acre oil can also be pricey, starting at $26.99 for a single 16-ounce bottle.
Wang said fermented oil is particularly good for the environment in comparison to palm oil, which is widely used in baking, cooking and in packaged foods. The production of palm oil has been a major driver of deforestation, habitat loss and greenhouse gas emissions.
"With fermented oil production you're not killing trees," Wang said. "There's energy and water input but it's significantly less compared to palm oil."
• 5. Butter, lard and coconut oil
Butter, lard and coconut oil are often used for baking because they contain a lot of saturated fat, which is solid at room temperature and helps to provide structure and texture to baked goods. Health authorities recommend that you try to limit your intake of saturated fat to no more than about 13 grams a day - roughly the amount in two tablespoons of butter - because of its ability to increase cardiovascular risk.
In a large new study published in JAMA Internal Medicine on Thursday, researchers followed over 200,000 adults for three decades and found that those who regularly consumed a lot of butter had a higher likelihood of dying early or dying from cancer. But higher intakes of plant oils such as olive oil and canola oil were associated with a lower risk of dying from cancer and heart disease.
Two plant oils you should be cautious about, however, are coconut oil and palm oil. Both are high in saturated fat and have been shown in studies to sharply increase LDL cholesterol, the kind that is associated with an increased risk of heart disease.