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How healthful an oil is to cook with mostly depends on how it reacts when heated. Generally, olive oil, avocado oil, and canola oil are healthful for cooking with.
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.
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.
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.