Oil reaches its smoking point once it starts to smoke and break down. Once it passes the smoking point, it releases free radicals that can cause damage to cells in the body.
Oils with high smoke points may be more stable and more healthful to cook with than those with low smoke points. The stability of an oil depends on how tightly packed the fatty acids in them are. The more tightly packed, the harder they are to break apart when heated.
Saturated and monounsaturated fats are the most stable oils to cook with. Higher levels of saturation in oil mean that it is more resistant to oxidization, the process wherein the acids break apart.
Polyunsaturated oils contain short-chain fatty acids and break apart more easily when heated, releasing more free radicals. Polyunsaturated oils are best to use unheated, such as by drizzling them over food or using them in dressings.
In this article, we take a look at the oils most healthful for deep frying, shallow frying, and roasting, along with other things to consider when choosing a cooking oil.
Most healthful oils for deep frying
One study found that extra virgin olive oil and coconut oil were two of the most stable oils. The researchers heated 3 liters of oil in a deep fryer at 356°F (180°C) for 6 hours. This suggests that they may be the most suitable oils for deep frying.
Olive oil has anti-inflammatory properties and is high in antioxidants and fatty acids. This makes it a more stable oil when heated at high temperatures.
Coconut oil comprises 92% saturated fat, and its resistance to oxidization makes it a stable cooking oil. One study showed that coconut oil was still stable after 8 hours of deep frying.
Due to its high saturated fat content, it is best to use coconut oil in moderation. Research has suggested that coconut oil raises both high-density lipoprotein (HDL), or “good,” and low-density lipoprotein (LDL), or “bad,” cholesterol levels more than unsaturated oils but less than butter.
The same review suggested that coconut oil may not be suitable for deep frying, however, due to its low smoke point. As a result, it may be better for shallow frying.
There are also studies that suggest that smoke point may not be the most important factor in the safety of oils when heated.
The authors of a 2018 study suggest that oxidative stability is more important than smoke point when looking at how healthful cooking oils are. In this study, coconut oil had high stability after heating.
Most healthful oils for shallow frying
Avocado oil is good for shallow frying.
Along with coconut oil and olive oil, avocado oil is a good oil to use for shallow frying. Avocado oil contains high levels of monounsaturated fat, which means that it stays fairly stable when heated.
Avocado oil raises the levels of good cholesterol in the body and lowers the bad. It also contains vitamin E, which is an antioxidant that may help reduce free radicals in the body.
People can use sunflower oil for shallow frying. It has a high smoke point and is also a good source of vitamin E.
Sunflower oil contains high levels of omega-6, however. Consuming too many omega-6 fatty acids can cause inflammation in the body. As a result, it may be best to use sunflower oil in moderation.
Canola oil is another oil with a high smoke point, making it suitable for shallow frying.
Most healthful oils for roasting
When choosing an oil to use for roasting, it may be best to choose one that has a high smoke point.
Oils with relatively high smoke points include coconut oil, peanut oil, and sunflower oil.
Olive oil is one of the more healthful oils, but its smoke point is slightly lower than that of the above oils. As a result, it may be best to use when roasting at a temperature lower than 374°F (190°C).
Avocado oil has a similar stability to olive oil at that heat.
Other healthful oils
The following oils have fairly healthful nutrition profiles. Some are more suitable for use in cooking than others, however.
Also called groundnut oil, peanut oil is high in monounsaturated fat, which makes it suitable for cooking. However, it does contain polyunsaturated fats as well.
It also has antioxidant and anti-inflammatory properties.
Canola oil is suitable for frying. Some research suggests that it can improve insulin sensitivity and help reduce cholesterol levels compared with other sources of fat.
Flaxseed oil is full of omega-3 fatty acids, which are essential fats for the body, and which may help prevent health conditions such as heart disease.
Flaxseed oil oxidizes easily, so it is best for drizzling over salads or food after cooking. It is best to keep it in a dark, airtight container in the fridge to prevent it from turning rancid.
Considerations when choosing a cooking oil
Oils that contain lower levels of linoleic acid, such as olive and canola oil, are better for frying.
Polyunsaturated oils, such as corn, sunflower, and safflower, are best for using in dressings rather than cooking with.
The American Heart Association (AHA) recommend that people choose oils containing less than 4 grams of saturated fat per tablespoon. They also advise people to avoid partially hydrogenated oils and trans fats.
Oils and fats to avoid
Trans fats increase LDL, or “bad,” cholesterol in the body and increase inflammation. This can increase the risk of heart disease, diabetes, and stroke.
Trans fats are present in processed foods, such as some store-bought cakes, donuts, cookies, and fast foods. Commercial deep-fried foods may contain trans fats if the manufacturers have cooked them in partially hydrogenated oils.
Trans fats also occur naturally in small amounts in animal fats, such as milk and meat.
People should also avoid heating oils at or above 375°F (190.5°C), as this can increase the chances of a toxic compound called 4-hydroxy-2-trans-nonenal (HNE) building up. HNE can increase the risk of health conditions such as liver disease, Parkinson’s disease, and stroke.
HNE can start to build up after just one use, and reheating the same oil to a high temperature can cause HNE to accumulate even further.
Healthful alternatives to using fats and oils
Spray oil is a healthful alternative.
People can also cook many foods without using fats or oils. Some alternative options include using the following:
- a small amount of stock or water to fry or roast foods in
- nonstick pans
- a spray oil, which helps a person use less oil when cooking
Using other liquids in cooking can add flavor and create an easy sauce for the dish, such as:
- cooking sherry
- tomato juice
- lemon juice
Oils high in monounsaturated fats are best for cooking with due to their stability when heated, as well as their potential health benefits. Examples include olive, avocado, and canola oil.
Coconut oil is also a stable fat to cook with. It may be best to use it in moderation due to its high saturated fat content, however.
Polyunsaturated oils are not suitable for cooking with due to their high rate of oxidization, but they could provide health benefits when a person uses them raw.
It is best to avoid trans fats and high quantities of saturated fats, as these can increase the risk of health conditions such as heart disease and diabetes.
The cooking oils in this article are available to purchase online.
Shop for extra virgin olive oil.
Shop for coconut oil.
Shop for avocado oil.
Shop for canola oil.
What is the most healthful method of frying?
People can enjoy fried foods occasionally, but they should be mindful about a few things when they decide to indulge.
Firstly, they should fry the foods in their own kitchen so they can control how much oil they use. Choose a fresh, clean, heart-healthy oil with a high smoke point, and stick to appropriate temperatures using a thermometer. Use little to no batter, and always drain excess oil. Finally, try to pair the fried food with a healthful side dish.
Katherine Marengo LDN, RD
Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.