Which cooking oils are the healthiest to use?

When even registered dietitians disagree on which cooking oils are best to avoid and which are safe, it’s hard for the average home cook to make a healthy choice. The grocery store shelves offer so many choices — avocado, vegetable, canola, grape-seed, peanut, sesame seed, sunflower seed, flaxseed, safflower, soybean, palm, coconut and olive oils. 

That said, experts agree extra-virgin olive and cold-pressed avocado oils are healthy. First, both have what is called a high “smoke point,” which is the level of heat they can tolerate before they start burning, breaking down and losing their nutritional benefits. Avocado oil has a higher smoke point than extra-virgin olive oil, so it is the best choice when using high heat, says Maya Fussell, a registered dietitian at Yale New Haven Hospital. 

When cooking oil breaks down, it oxidizes, which can contribute to heart disease risk, according to a study published in Vascular Pharmacology. When cooking with oils, be sure to use your oven vent. Oils that reach their smoke point and burn release an airborne substance called acrolein that can be dangerous to your lungs, according to a study in PubMed.

“If you’re making dressing or cooking something fast on the stove, like stir-frying vegetables, use extra-virgin olive oil,” Fussell says. She recommends using extra-virgin olive oil with vinegar and water when making salad dressing at home, but using a bit more vinegar and water to cut the standard three-to-one ratio of olive oil to vinegar. Avocado oil is pricier than extra-virgin olive oil, so it can be saved for cooking at higher temperatures. 

More budget-friendly options are olive and canola oils, Fussell says. Olive oil is more processed than extra-virgin olive oil, but still contains omega-3 fatty acids and offers health benefits. Home cooks can also pour in a bit of wine and water to lessen the amount of cooking oil needed. Canola oil is processed, but Guy Crosby, an adjunct associate professor of nutrition at the Harvard T.H. Chan School of Public Health, writes, “canola oil is a safe and healthy form of fat that will reduce blood LDL cholesterol levels and heart disease risk compared to carbohydrates or saturated fats such as found in beef tallow [rendered fat] or butter. Indeed, in a randomized trial that showed one of the most striking reductions in risk of heart disease, canola oil was used as the primary form of fat.” 

However, another registered dietitian, Alyssa Adler, with Nuvance Health Bariatric and General Surgery department at Norwalk Hospital, suggests avoiding canola, sunflower, cotton seed, sesame seed, grape seed and corn oils. “These oils are heavily processed and they lose a lot of nutrients that way,” Adler says. 

One common misconception is that the omega-6 fatty acids in seed oils are bad, Fussell says, pointing out that the argument that consuming omega-6 increases people’s risk for inflammation and metabolic disease is flawed. “We don’t have evidence that an increase in omega-6 in the diet increases heart-disease risk.” In fact, in a 2019 article in the American Heart Association’s journal, Circulation, an analysis of 30 studies from 13 countries about the role of omega-6 fatty acids in cardiovascular disease concluded that higher levels of omega-6s were associated with lower risks of heart events. 

In the Mediterranean diet, which is widely recommended as the healthiest way to eat to prevent heart disease, cancer, dementia and other illnesses, the ratio of omega-6 to omega-3 is five-to-two, and that’s okay, Fussell says. Omega-6 is a problem in the typical Western diet because the ratio of omega-6 to omega-3 is 10-to-one.

Fussell recommends avoiding ultra-processed foods as much as possible and cooking at home for most meals rather than eating out. “The food industry uses vegetable oils in ultra-processed foods, but more concerning is the abundance of refined carbohydrates, added sugars, saturated and trans fats found in the foods. Instead of thinking of decreasing omega-6s, it’s [more practical] to increase omega-3s through whole-food sources, such as fish, walnuts and seeds,” Fussell says. “Choose whole foods as much as you can.”

Vegetable oils get a bad rap because of the way they’re used in processed foods and in the restaurant industry to fry foods, Fussell says. When restaurants reuse and reheat vegetable oils repeatedly, “that’s when oils produce unhealthy byproducts like trans fatty acids,” she says. “Cooking with vegetable oil at home is not an issue.” If your budget allows, the dietitians say, extra-virgin olive and avocado oils are superior. Standard cooking oils are refined, bleached and deodorized before being bottled for consumers, while extra-virgin olive oil is cold pressed and untreated by heat or chemicals. 

Coconut oil is another cooking oil that generates mixed messages from dietitians and researchers. Adler says some people say the presence of medium chain triglycerides (MCTs) can help with weight loss and lessen inflammation, but WebMD says there’s no evidence to back this up. Both Adler and Fussell say coconut oil is high in saturated fats, which makes it bad for heart health. Fussell recommends people “avoid any tropical oil, like palm and coconut oil,” which are solid at room temperature. “Anything liquid at room temperature is going to be a better option.”

Both registered dietitians recommend people read labels on processed foods — even if you’ve eaten them for years or they’re vegan. Mayonnaise contains soybean oil; oat milk contains sunflower oil; vegan cheese contains coconut oil; and vegan butter contains palm, soybean and canola oil. “If you were to get” a veggie burger, Adler says, “what are they using in there? Are they using soy protein? Are they adding extra preservatives to make the same texture and taste as a meat product?” 

 The bottom line, Adler says, “Always read the labels.”