Healthy Living

Cooking Oils: Which One When, and Why?

Jun. 15, 2015
Which cooking oils do you keep on hand? And which occasion calls for which oil? UR Medicine Registered Dietitians offer this quick overview.
bottles of various cooking oils
What are the different types of cooking oils?
Probably the most common is vegetable oil. It’s usually derived from soy or corn, and it’s what a lot of restaurants use for cooking. Canola oil is a type of vegetable oil made from rapeseed. Then you have olive oil, coconut oil, avocado oil, and lots of specialty nut and seed oils, which come in distinct flavors like sesame, walnut, or hazelnut. These are just the biggies. There are many more out there on the market.
Do they all do the same thing?
Fundamentally, all oils are made of fat and are liquid when stored at room temperature. Fats are essential to building healthy nerves and skin, and to helping us absorb nutrients. In cooking, fats are used for heat transfer, to brown food, and for flavor.
You’ll want to choose your oil based on what temperature you’ll be cooking at and what flavor you’re aiming for. You may have heard of oil’s “smoke point”—this is the temperature its fats start to break down and form unhealthy compounds (a.k.a., free radicals). If you’ve hit this point, you’ll see and smell the smoke, and the oil will scorch what you’re cooking.
Some oils hold up to high heat better than others. 
  • Cooking at high heat? Choose oils with a high smoke point. These are more refined ones, like a refined olive, avocado, or coconut oil. Cooking methods using high heat include roasting, broiling, grilling, pan frying, or deep frying (not recommended!).
  • Cooking at medium heat? Go with a less refined olive oil, peanut oil, or any of the high heat oils. Cooking methods using medium heat would be a quick sautée or cooking in the oven at temperatures of less than 300 degrees.
  • Cooking at low heat? Try nut, seed, or canola oil. (Bonus: Canola is high in those good-for-you omega-3 fatty acids.) These can be added as a raw ingredient in salad dressings or used to flavor foods at the very end of the cooking process.
How do they vary by taste?
Some are definitely stronger, and some more neutral. When you taste those specialty nut and seed oils—some of which are flavored with additional herbs like garlic—you’ll definitely know it’s there, whereas the vegetable and canola oils are more subtle. So you wouldn’t want to use those with the goal of flavoring food.
What’s the best way to store cooking oil?
When oils are exposed to oxygen, heat, and light, they go rancid and start to form toxic compounds. You can smell it—you’ll unscrew the bottle and recoil. You’d be able to taste rancidity in oil, too.
If your oil is rancid, get rid of it. At that point, its nutritional value is gone, and consuming it poses the potential for long-term health effects.
Proper storage can prolong the shelf life of your oils. Keep olive, canola, and coconut oils in a cupboard, away from heat (the stove) and light.
Seed and nut oils do best in the fridge.
Does one type of oil emerge as the go-to?
Olive oil is versatile, ranging in flavor, use, and price. You can accomplish most of your cooking tasks with just two types of olive oil.
If you opt for extra virgin olive oil, you’ll get the most bang for your buck. This is the first press of the olive, meaning it has the most vibrant olive taste. It’s less refined (read: has been put through fewer processes) and is nice for dipping or salad dressings.
Then you have virgin olive oil (more refined than extra virgin). And finally, there’s pure, 100 percent olive oil, the most refined—those olives have been through multiple pressings and can be used for moderate and high-heat cooking.
Try subbing olive oil in for your butter next time you bake! You’ll end up with noticeably moister sweet treats. Butter is a mixture of fat and water, so you’ll only need about 75 percent oil to each part butter.
This information is provided by the Food and Nutrition Services Department at UR Medicine’s Strong Memorial Hospital.