What Is the Healthiest Cooking Oil for Deep Frying?

Deep frying is a cooking method that seals in the moisture, resulting in a crispy surface and enhanced taste and texture. When choosing the best oil for frying, consider the characteristics of each product, including how it's processed, thermal stability, viscosity and overall health benefits.

One of the most important considerations when selecting the best oil for frying is how it will react when heated. Deep frying involves using a cooking temperature higher than 212 degrees Fahrenheit (the temperature of boiling water). Cooking oil can be brought to much higher temperatures, which are required to create that delicious crispy browning effect.

The temperature that causes a particular oil to start to burn and oxidize is called the "smoke point." Heating cooking oil to a higher temperature than its smoke point causes degradation that can produce toxic fumes and harmful free radicals. Some of these by-products can have adverse effects on health, warns a May 2018 research article in ​ACTA Scientific Nutritional Health.​

When deep-frying, it's important to choose an oil with a high smoke point. According to the Canola Council, frying requires maintaining the oil temperature at 365 to 375 F.

Adding food to the oil will initially lower the temperature, so it's best to preheat the oil to about 15 F higher than the optimal deep-frying temperature. Therefore, you should use oils with a smoke point of around 400 F. Those with a lower smoke point may not withstand high heat, so they may be the healthiest oils for pan-frying or low-temperature cooking.

Cooking oils rich in saturated and monounsaturated fats generally have the highest smoke points and are more resistant to oxidation, according to a May 2015 study in ​Advances in Nutrition​. Conversely, those high in polyunsaturated fats degrade more easily because they contain short-chain fatty acids that break apart when heated.

Several processes are used to extract oil from plants, seeds and nuts. This can be done through the use of pressure, such as cold-pressing, or mechanical, thermal or chemical processes.

Manufacturers refine the oil to ensure purity and clarity, decrease rancidity for longer storage and make their products more resistant to smoking. The more refined the oil, the higher the smoke point, according to the American Council on Exercise.

But, the refining process affects not just the flavor but also the levels of polyphenols, which help protect your cells from oxidative damage, per PennState Extension. Processing may also reduce the micronutrients in oil as well as its antioxidant activity and create lipid degradation. This will ultimately affect the potential health benefits of oil, per a March 2019 study in ​PLOS One​.

Most oils you find on supermarket shelves are refined, although many are also available unrefined, albeit often expensive. Whenever possible, choose oils with high smoke points in their most natural form, such virgin, unrefined or cold-pressed versions.

Following is a comparison of smoke points of some common oils that can withstand high cooking temperatures, according to the Canola Council of Canada and the Harvard T.H. Chan School of Public Health:

Your body needs fats to function properly. Fats are integral to cell structure and help maintain muscle contraction, blood clotting, immune function and blood pressure, according to the American Council on Exercise.

This nutrient is also required for the absorption of fat-soluble vitamins, such as vitamins A, D, E and K. The Dietary Guidelines for Americans recommend that you get 25 to 35 percent of your daily calories from fat.

The fat in oil comprises a mixture of fatty acids, both saturated and unsaturated. Unsaturated fats, which include monounsaturated and polyunsaturated fatty acids, are the healthiest choice.

Polyunsaturated fats include omega-3 and omega-6 fatty acids that help form hormone-like compounds needed to regulate bodily functions. Omega-3s play a role in reducing inflammation and protect against diseases, such as arthritis, lupus and asthma, per PennState Extension. Omega-6 fatty acids increase inflammatory response to infection and injury. They help increase clotting and restrict blood vessel size, reducing bleeding.

Monounsaturated fats are liquid at room temperature and turn solid when chilled. Oils rich in monounsaturated fats, such as oleic acid, may help reduce LDL (bad) cholesterol levels and protect against cardiovascular disease. These healthy fats also contribute the antioxidant vitamin E to your diet, according to the American Heart Association.

Saturated fats can be found in oils that are solid at room temperature. They may negatively affect your health and lead to heart disease and weight gain, states the U.S. National Library of Medicine. Oils that contain the most saturated fat include tropical oils, such as coconut and palm oils. The Dietary Guidelines recommend limiting your intake of saturated fat to less than 10 percent of your calories.

The following chart compares the amount of saturated, monounsaturated (MUFA) and polyunsaturated fats (PUFA) in 100 grams (3.5 ounces) of various oils with a medium-to-high smoke point.

In general, the lower the amount of saturated fat and the higher the content of unsaturated fat, the healthier the oil is.

Trans fats form when vegetable oils are hydrogenated into shortening and stick margarine. This results in partially hydrogenated oil, which can negatively affect your health and increase the risk of heart disease, according to a study in the July-August 2016 issue of ​Indian Heart Journal.​

Some of the best oils for frying have a high smoke point, contain healthy monounsaturated fats and are low in saturated fats. These include olive, canola, corn and safflower high oleic oils.

Extra virgin olive oil (EVOO) is an integral component of the Mediterranean diet. It's rich in monounsaturated fats, which makes it less likely to oxidize at high temperatures.

Even though it has a lower smoke point than some other oils, it can be used for frying. According to the study in ​ACTA Scientific Nutritional Health,​ additional factors, such as oxidative stability, may also play an important role in determining the suitability of use in high-temperature cooking.

Researchers heated extra virgin olive oil to 464 F and maintained it at 356 F for 6 hours. EVOO yielded lower levels of oxidative by-products compared to other oils tested — virgin olive oil, olive oil, canola oil, rice bran oil, grapeseed oil, coconut oil, peanut oil, sunflower oil and avocado oil. Its fatty acid profile and antioxidant content were the most stable, followed by coconut oil and other virgin oils, like avocado and high oleic acid seed oils.

A May 2017 ​Comprehensive Reviews in Food Science and Food Safety​ study reports similar findings: Olive oil performed similarly or better than other vegetable oils when heated, and frying with virgin olive oil and EVOO is linked to disease prevention, reduced insulin resistance and a lower risk of heart disease.

Canola oil is another good choice. It's typically sold as refined oil and extracted using heat and a solvent called hexane. There has been some concern that hexane may affect its stability, destroy omega-3s and even create trans fats, according to the Harvard T.H. Chan School of Public Health.

But researchers say there is no evidence to confirm that hexane poses any health risks, considering the small amount ingested from canola oil. Plus, due to deodorizing during refinement, canola oil contains very low levels of trans fat, although this process also reduces its levels of omega-3s.

High-oleic canola oil contains more monounsaturated and less polyunsaturated fats. This makes it more stable, allowing for greater heat tolerance and a better choice for deep frying when compared to other oils high in polyunsaturated fats, such as corn, peanut and safflower, per the Canola Council.

You can also opt for sunflower oil. Although it has a high smoke point, a June 2017 study in the ​European Journal of Nutrition​ reported that using sunflower oil for frying increases DNA oxidative damage after ingestion, whereas virgin olive oil has the opposite effect.