Can Cooking Oils at High Heat Lead to Cancer? Experts Answer

If we use oil which has been repeatedly heated, then it’s potentially carcinogenic due to free radicals.

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Vegetable oils can release potentially harmful compounds when heated and those compounds have been linked with cancer.
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The conversation around using oils at the right temperatures when it comes to cooking is kind of an eternal one, even if not too mainstream in the health parlay just yet. However, it is important to note that oils, if not used correctly, might become dangerous for your health in ways you may have not paid attention to so far. On the other hand, oils also don’t have to be damned as the evil they are often made out to be. Let’s dive into this deeper.

What is Good Oil and What Isn’t?

In terms of nutrition, it’s important to remember that oils are a calorie-rich food item. Most are high in the “good” polyunsaturated and monounsaturated fat, but some do have significant amounts of the “bad” saturated fat.
Seema Singh, Chief Clinical Nutritionist, Fortis Hospital, Vasant Kunj, New Delhi

If you want to get into the specifics of it, Ritika Samaddar, Regional Head, South Zone, Dietetics, Max Super Speciality Hospital, Saket, New Delhi, says,


"Oils that contain saturated, polyunsaturated and monounsaturated fatty acids in the ratio of 1:1:1 are considered to be ideal for consumption. Unfortunately, this ratio is not present in any of the oils that are commonly available. Instead we should aim for an oil nearing this ideal ratio. It can be achieved with rotation/right combination or use of blended oils."

What Kind of Oil Should We Use For Cooking?

Coconut oil is popular in south Indian cooking.
Coconut oil is popular in south Indian cooking.
(Photo: iStockphoto)

Singh says that seed oils are better, as is ghee, when used in a limited quantity. Along with this, there are the usual options of coconut, mustard and groundnut oil for daily use. When it comes to sautéing over medium flame or roasting below medium temperature, she recommends olive, peanut, sesame and canola oil. To this list of oils suitable for sautéing or light cooking, Samaddar adds some more, while also reminding us of their importance in our diet.

"Oil is required to provide the essential fatty acids – omega 3, 9 and 6 for a healthy brain and heart. Fat is essential for absorption of fat soluble vitamins A, D, E and K, while also giving satiety value and palatability to food. But look for healthy option – this includes canola oil, mustard oil, rice bran oil, peanut oil. Omega 3 fats include olive oil and oils from nuts and seeds like almond and flaxseed. Cold pressed oils are also a good option as cold pressing of oils at low temperature retains naturally occurring phytochemicals, such as polyphenols and plant sterols, as well as Vitamin E."
Ritika Samaddar

Oil and Heat - A Complicated Relationship

Oil and heat
Oil and heat
(Photo: iStock)

However, when it comes to high temperatures, there are a couple of things that need to be kept in mind during consumption.


“Indian cooking requires frying at a high temperature. Vegetable oils can release potentially harmful compounds when heated and those compounds have been linked with cancer,” says Singh, adding:

"If we use oil which has been repeatedly heated and has become dark in colour, then it’s potentially carcinogenic due to free radicals. Reheating can further damage the components and produce more toxic compounds that are highly harmful for the heart. Reusing the same oil repeatedly (for instance, for frying) has been analysed to reveal its detrimental effects on the body."
Seema Singh

Ms Samaddar delves deeper into the science of it and explains:

"Smoking point of oil refers to the temperature to which the oil/ ghee produce smoke or starts to oxidize. Most oils have a smoking point of higher than 200 degree centigrade. The cooking temperature of food is around 120-180ºC (for sautéing it is around 120ºC, for deep frying - 180ºC). So, most oils and ghee are safe. What one needs to be careful about is the duration of heat, and also of the reuse of the oil."
Ms Samaddar

Oils and their Smoking Point


● Most refined oils like sunflower, corn, mustard, rice bran, pure olive oil, canola oil: a smoking point of around 230-250ºC
● Coconut oil: 150ºC
● Ghee: 220-250ºC
● Butter: 175ºC
● Extra virgin olive oil: 170-190ºC

Samaddar emphasises the harms of reheating and overheating again, reminding you that overheating can break down the oil which results in the realise of free radicals that can harm the body. “Heating and reheating oil can transform it to trans fat which not only raises the bad cholesterol (LDL) levels, but also lowers the good cholesterol (HDL) levels. Additionally, it increases insulin resistance, and thus the chances of diabetes, along with being carcinogenic.”

Heat, Light and Air - The Final Piece of Advice

Samaddar lists down heat, light and air as the “the three villains” that are working against the health benefits of your oil. This is how she explains it:

  • •Sunlight degrades the quality of oil hence keep it in a dark-coloured bottle. Excessive heat or prolonged exposure to light will speed up deterioration of flavour. Temperature around 30 ºC is ideal.

  • If the oil has constant access to fresh air, the process of oxidation starts and it deteriorates faster. The bottle should have a tight fitting cap to avoid this.

  • Keep the oil in clean and dry containers because exposure to moisture will subject it to oxidation, eventually leading to rancidity.

(Rosheena Zehra is a published author and media professional. You can find out more about her work here.)

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