“Olive oil, due to its chemical structure, is susceptible to oxidative damage when heated,” says thekitchenskinny.com. “When it comes to high heat cooking, coconut oil is your best choice,” says healthline.com. Befuddled about which oil to use? Here’s how one expert clears up the confusion.
“Coconut oil is the best oil you can use for cooking because it can resist heat-induced damage, so you can avoid ingesting oxidized fats,” says mercola.com.
Oxidative stress—that is, an excess of free radicals caused by oxidation—may damage DNA and raise the risk of cancer, heart disease, and other illnesses. But your oil is unlikely to become oxidized in the frying pan or wok.
“For the amount of time you’re going to cook, and the temperatures you’re going to get to, your oil is not going to undergo oxidation,” explains Eric Decker, an oil expert and chair of the department of food sciences at the University of Massachusetts Amherst.
What’s more, adds Decker, “every oil naturally contains vitamin E, which is an antioxidant.”
Extra-virgin olive oil has another plus. “It isn’t refined, so it has a lot of naturally occurring antioxidants.”
Decker’s take-home message: don’t worry about oxidizing oils on your stovetop. “If you’re just pan-frying, no oxidation probably occurs. Even with deep-fat frying at home, oxidation is minimal.”
So fear of frying is no reason to stop using monounsaturated oils (olive, peanut, canola) or polyunsaturated oils (soy, corn, sunflower), which lower LDL (“bad”) cholesterol, and switch to coconut oil, which raises LDL.
Some oils do hold up better at high temperatures, though. Any oil starts to degrade once it reaches its smoke point, which varies from oil to oil. “If you put oil in the pan and heat it too much or let it go too long, the oil starts smoking,” Decker says.
And then you could be in trouble. “The smoke point is followed by the flash point,” notes Decker. “That’s when your oil catches on fire.” If you accidentally let your oil smoke, get rid of it and start over.
Refining an oil raises its smoke point by removing impurities, which is why refined oils—like most canola, soy, and peanut, as well as “light” or “pure” olive oil—work well for high-temperature cooking.
Do oils ever become oxidized? Yes, but it’s easy to tell when that happens. “When oxidation occurs, the fatty acids break into small molecules, which have a smell,” says Decker. “That’s what we call rancidity.”
But a high temperature isn’t the biggest cause of oxidation, says Decker. It’s time.
“I just cringe when I see people buying five-gallon containers of soybean oil, because there’s no way—unless they’re deep frying every day—they’re going to use it up before it goes rancid.”
While all oils can become oxidized, “the more unsaturated the fat is, the more susceptible it is,” adds Decker.
What to do
“Buy smaller bottles and store them in the refrigerator,” says Decker. “That’s what I do at home. And if your oil smells bad, don’t use it.”
There’s no need to keep olive oil cold, though. “It will harden in the refrigerator,” says Decker. “Plus, it’s more stable than polyunsaturated fats. So you can keep it at room temperature.”
The bottom line: For home cooking, almost any oil should be fine. Coconut oil? For your heart’s sake, leave it on the shelf.