Between the dozens of choices, emerging food fads, and the fuzzy facts you vaguely recall, choosing the right cooking oil can be confusing. To help you wade through the information—and choice—overload, here are four things to know about cooking oils.
Bad Fats, Good Fats
There are three types of dietary fat: unsaturated fat, saturated fat, and trans fat. The two harmful fats are saturated fat and trans fat. Saturated fat is primarily from animal products such as meat and full-fat dairy products. Although there are trace amounts of trans fats in natural food, the vast majority of trans fat is found in processed food, through a process called partial hydrogenation. Trans fats are a double whammy that increases the “bad” (LDL) cholesterol while also lowering the heart-healthy “good” (HDL) cholesterol. The American Heart Association (AHA) suggests less than 7 percent of total daily fat should be from saturated fat, and trans fats should constitute less than one percent or be completely eliminated.
Unsaturated fat is actually beneficial, and can boost HDL cholesterol while lowering LDL cholesterol. Unsaturated fats can be further broken down into monounsaturated and polyunsaturated fats. The two most common polyunsaturated fats in plant oils are the essential nutrients omega-3 fatty acid alpha-linolenic acid (ALA) and omega 6 fatty acid-linoleic acid (LA). These nutrients are essential because the body cannot make them and must obtain them through diet.
All cooking fats and oils are a blend of saturated, monounsaturated, and polyunsaturated fats. Plant oils—which can be high in heart-healthy omega-3s—help the body absorb nutrients (vitamins A, D, E, and K) and provide antioxidants such as vitamin E and selenium and essential nutrients like ALA. When used in place of saturated fat (like butter or tropical oils), plant oils may help reduce the risk of heart disease and stroke—the number one killer in the United States—by lowering LDL blood cholesterol and blood pressure and reducing inflammation.
Smoke ‘em and Store ‘em
The smoke point of an oil is the temperature at which the oil starts to break down, lose nutritional value, and literally starts to smoke, potentially imparting a bitter, unpleasant taste to your food. Oils with a high smoke point, like peanut, are good for deep frying, whereas no-heat oils like walnut are best highlighted in a salad.
How oils are stored also impacts their nutrition content. Heat, light, and oxygen damages most oils, so it is important to store them tightly capped in a cool, dark place. Oils high in polyunsaturated fats like walnut or flaxseed oil should be stored in the refrigerator. Over time, all oils will degrade and should be tossed if they smell bitter or “off”.
Which to Use…
Canola oil is comprised mostly of monounsaturated fat (62 percent monounsaturated fat, 31 percent polyunsaturated fat, and 7 percent saturated fat)1 and contains the second highest level of ALAs, behind flaxseed oil. It has a moderately high smoke point and light flavor, making it versatile in the kitchen. Canola can be used for sautéing and stir-frying, and is great for baking as a replacement for solid fats such as butter or margarine. When using canola oil, organic is a must as most canola oil produced in the United States is genetically modified.
Olive oil is high in monounsaturated fat (78 percent monounsaturated fat, 8 percent polyunsaturated fat, and 14 percent saturated fat).1 “Light” olive oil, labeled for its color, is more refined, and has a neutral flavor and high smoke point. It works well for everything from stir-frying to sautéing and frying. Extra-virgin olive oil is minimally processed, contains more antioxidants and vitamin E, and has a bold, fruity flavor. Extra-virgin olive oil has a medium-low smoke point and can be used in dressings, marinades, sauces, and pastas. Not all extra-virgin olive oil is the real deal; use this guide to ensure you’re getting what you pay for.
Avocado oil is mainly monounsaturated fat (65 percent monounsaturated fat, 18 percent polyunsaturated fat, and 17 percent saturated fat), making it a heart-healthy choice.1 Avocado oil has a high smoke point, making it ideal for sautéing and frying. It also offers a delightful, sweet aroma, making it a superb finishing oil in salads. Cold-pressed is less refined and contains antioxidants and sterols but is less stable and has a lower smoke point.
Flaxseed oil is rich in monounsaturated fat (65 percent monounsaturated fat, 28 percent polyunsaturated fat, and 7 percent saturated fat) 1 and an excellent source of ALA. Flaxseed oil shouldn’t be heated and is best stored in the fridge. It can be used in salad dressings, spreads, and dips.
… and Which to Lose
Tropical oils—coconut, palm, and palm kernel—are mostly made of the bad-for-you saturated fatty acids. Coconut oil, for example, is 6 percent monounsaturated fat, 2 percent polyunsaturated fat, and a whopping 92 percent saturated fat.1 These tropical oils have been recently been hyped due to their unusually high proportion of medium-chain triglycerides (MCTs), which some studies suggest can help burn extra calories and expedite weight loss. However, most research on MCTs and heart health studied MCTs that are structured differently than those found in tropical oils (those with eight and 10 carbon chains versus coconut oil’s 12-long chains). Moreover, although some studies backed MCT-rich coconut oil as a weight loss supplement, about an equal number of other studies disputed those findings. Dubious claims of expedited calorie burning aside, due to their high saturated fatty acid content, these oils are an undesirable choice for heart health.2
Most “vegetable oils” are made from soybeans, corn, palm, or safflower, or even a combination thereof. These oils are high in omega-6 fatty acids, which are far more ubiquitous in the American diet than their heart-healthier omega-3 cousin. The American diet high in omega-6 fatty acids appears to contribute to inflammation and chronic disease.3 The AHA recommends keeping omega-6 polyunsaturated fatty acids as low as 5–10 percent of an adult’s daily caloric intake.
So forget the oil-free cooking YouTube videos or faddish fat-free diets. Being smart about eating fats—which kinds and in what ways—can help you stay fit and heart healthy.