Do Cooking Oil Smoke Points Really Matter? Experts Break It Down

Have you ever accidentally left an oil-greased pan heating on the stove, only to turn around to find billowing smoke filling the air? That means the oil has officially reached its smoke point, or the temperature at which it starts to burn and produce smoke. Aside from the fact that cooking in burnt oil makes for a pretty gnarly-tasting dish, regular exposure to improperly heated oils may have some detrimental effects on your health, too.

"Oils are composed of molecules known as triglycerides, which are further made up of glycerol bonded to three fatty acids," says Bryan Quoc Le, Ph.D., food scientist, food industry consultant, and author of 150 Food Science Questions Answered. "The smoke point is the temperature at which these fatty acids begin to break down under heat, as they are vaporized and react with oxygen in the air." In other words, when the fats in the oils are, well, oxidized.

It's worth noting that while this is a general guideline, the type of processing matters, too. "Clarified and refined oils will have been stripped of most of their fatty acid content and therefore be more resistant to higher temperatures. Oils with high fatty acid content will have smoke points at lower temperatures," says Le. In other words, refined coconut oil has a higher smoke point than raw coconut oil.

So, why is smoke point important? For starters, low-level exposure to acrolein, the byproduct found in the smoke from burnt oil, can irritate your eyes, nose, and throat1. And while that's acutely unpleasant, the bigger issue is repeated exposure.

"Unfortunately, there is more harm to heating an oil past its smoke point than the irritating smoke it produces," says Lindsay Wengler, M.S., R.D., CDN, CNSC, registered dietitian at Olive Branch Nutrition in NYC. "Not only can an oil heated beyond its smoke point catch fire, but the molecular breakdown of the oil can create pro-inflammatory free radicals and a carcinogenic compound, acrolein, which may be harmful to your health." 

Ferira explains the mechanisms of this problematic aldehyde compound further: "Acrolein is highly reactive and over time can mess with DNA by cross-linking it. It also has the potential to get in the way of essential detoxifying enzyme systems in the liver like cytochrome P450 and throughout the body by inhibiting glutathione pathways."

Regular acrolein exposure has also been associated with heart disease2 and various other diseases3. But the key words here are "regular exposure." The occasional burnt oil isn't a big deal, but you don't want to make a habit of it.

Heating an oil past its smoke point can also negatively affect the flavor of your dishes. "Though we expect a little smoke in the kitchen from time to time, an oil's smoke point is an important thing to consider when cooking as it signals the breakdown and degradation of the oil, including its flavor and nutrient profile," she says, adding that acrolein can add a bitter and/or burnt flavor to your dishes.

Because smoke points vary so much, you'll want to be discerning about which oils you're using for different types of cooking. Wengler says that since avocado oil has one of the highest smoke points, it's a great option for high-heat cooking. Its neutral flavor also makes it extremely versatile since it won't overpower the taste of whatever you're cooking. It's a healthy oil, too, thanks to its high concentration of antioxidants and oleic acid, a monounsaturated omega-9 fat that is associated with managing weight and preventing heart disease5.

While canola oil, vegetable oil, and soybean oil also have relatively high smoke points, these more unhealthy oils are often highly refined and exposed to potentially harmful chemicals during the refining process, Cate Shanahan, M.D., previously told mbg. When exposed to these chemicals, they lose some of their antioxidants, vitamins, and minerals. They're also chock-full of omega-6 polyunsaturated fats (PUFAs), which can fuel inflammation6 in high amounts over time.