By Amy Gorin
When you're prepping a meal you may use whatever oil is easiest to reach. And for the most part, it seems like you can't go wrong. Most oils contain monounsaturated and polyunsaturated fats, which may lower "bad" LDL cholesterol levels when replacing a saturated fat like butter. Olive oil, for example, is a staple in the Mediterranean diet, and for good reason: It contains at least 30 phenolic antioxidant compounds, and regular consumption is associated with lower risk of obesity, heart disease, type 2 diabetes, and cancer (breast, colorectal, and prostate), shows Spanish research. But while certain oils, like olive, are heart-healthy, those benefits may be lost when used incorrectly.
A common mistake when cooking with oils is using a too-high heat on a low- or no-heat oil. Every oil has a smoke point, or a temperature at which smoke forms and the oil's compounds break down, releasing free radicals, degrading nutrients, and producing a rancid flavor. "Raising the temperature to the smoke point or beyond can destroy health benefits found in oils, especially in those with omega fatty acids," explains James Briscione, director of culinary development at the Institute of Culinary Education in New York City.
Oil degradation can also cause a food to absorb too much oil and become greasy. As for flavor, too-high heat destroys aromatic compounds in oils. This renders fine oils, like extra-virgin olive and sesame, nearly tasteless if cooked over high temps for too long, says Briscione.
Related: Making Sense of the Science of Fat
Interestingly, no matter an oil's smoke point, heating may reduce some of its antioxidant benefit, occurring on a more significant level at higher temperatures. For instance, when extra-virgin olive oil is heated to 194°F for 30 minutes, it loses between 0.4 and 2 percent of the antioxidant tyrosol. When that temperature is increased to 428°F, the loss rises up to 13 percent, shows a study in the journal Molecules.
Below is a primer on the best cooking oils to help maximize health perks (rather than watch them evaporate) and get more bang for every bite.
No-Cook and Light-Heat Oils
Types and smoke points: Flaxseed (no cook), hempseed (330°F), walnut (no cook)
Description: Most of these oils can't withstand heat and, therefore, shouldn't be cooked. The exception is hempseed oil, which can be lightly heated for a short amount of time. No-cook and light-heat oils are a good source of alpha-linolenic acid, a heart-healthy omega-3 fatty acid. Flaxseed oil may reduce LDL cholesterol, reported a study in The American Journal of Clinical Nutrition. Oils rich in omega-3s stay fresh longest when refrigerated.
Best for: Drizzle over a salad, or blend into a smoothie or dip.
Types and smoke points: Coconut (350°F), olive (extra-virgin, 320°F)
Description: Coconut oil is higher in saturated fat and lower in beneficial monounsaturated fat than many of its counterparts. The extra-virgin version is almost purely (92 percent) saturated fat. Although there's been a lot of hype about the oil's potential health benefits, it may raise both "good" HDL cholesterol and "bad" LDL cholesterol. So use coconut oil in moderation.
Best for: Use in a light sauté, a stovetop sauce, or low-heat baking.
Medium-High Heat Oils
Types and smoke points: Canola (400° F), grapeseed (392° F), macadamia (390°F), olive (virgin, 420°F), sesame (410°F)
Description: Olive and grapeseed oil are the stars of this group, best known for their pleasing flavors and versatile uses. "Olives are loaded with aromatic compounds, giving each variety of olive its own unique flavor," says Briscione. "Many other oils are made from parts of plants like seeds or kernels, which are essentially flavorless." Most chefs have two types of olive oil in their kitchen--a medium-quality extra-virgin oil for cooking and a high-quality extra-virgin olive oil for finishing foods, notes Briscione. A fine extra-virgin olive oil can be used for salad dressing, drizzling on soups or cooked vegetables, or in making pesto.
Best for: Use in a stir-fry or for roasting or baking.
Types and smoke points: Avocado (520°F), corn (450°F), olive (pomace, 460°F), olive (extra light, 468°F), peanut (450°F), soybean (450°F), sunflower (450°F)
Description: These oils can be used for both low- and high-heat cooking. While frying should be minimized, you can fry food at a lower temperature to make it healthier. This usually requires a longer cooking time, but it releases less oil into the food, allowing the food to absorb less oil. French fries cooked with this method--where raw potatoes are added to cold oil and gradually heated to a little below 280°F--contained 30 percent less oil than their conventionally prepared counterparts. When using sunflower oil, choose a high-oleic version, which contains a greater percent of monounsaturated fat. As for corn and soybean oils, these two oils are higher in omega-6 fatty acids, which experts previously recommended limiting for optimal health. However, those same experts are now rethinking this, in part due to new research suggesting that the oils may be good for you.
Best for: Searing, browning, and frying.