Sunflower oil danger: Why it's a lousy choice for frying

Do you know which oil to use for frying? Many people ponder the choice of the appropriate fat, especially when standing in front of a shelf filled with various oils in a store. One very popular oil should only be used cold. When heated, it releases harmful substances.

Sunflower oil is one of the most popular oils used in the kitchen, right after rapeseed oil. It is an inseparable ingredient in many dishes; we use it for frying and baking. Unfortunately, this is not a beneficial practice.

Sunflower oil (soybean, corn, grape seed, pumpkin seed, sesame oil) contains a predominant amount of polyunsaturated fatty acids, quickly oxidising under high temperatures. This means that during frying, the polyunsaturated fatty acids in sunflower oil break down into harmful substances, including those with potentially carcinogenic properties.

Moreover, scientists from De Montfort University and scholars from Oxford indicate that heated sunflower oil may release carcinogenic aldehydes. Therefore, it is better to use sunflower oil raw (e.g., in salads), and it is not recommended to fry with it.

For home frying, oils that contain many monounsaturated fatty acids (MUFA) and a few polyunsaturated fatty acids (PUFA) are best. Rapeseed oil and olive oil are examples of such oils. Monounsaturated fatty acids are more resistant to oxidation under high temperatures. And precisely because rapeseed oil contains about 61% monounsaturated fatty acids and 29% polyunsaturated fatty acids, it is suitable for both short-term frying and salads.

Most oils available in stores are sold in plastic bottles. These are usually refined oils, purified at high temperatures (over 160°C) and using chemicals. This means they have been stripped of impurities and important components. Refined oils can be used for frying because they have a higher smoke point. However, it is still better to fry with refined rapeseed oil than with refined sunflower oil; as mentioned, sunflower oil still contains more polyunsaturated fatty acids, which have an unfavourable fatty acid profile for frying.

Refining oil does not make it suitable for frying; it only raises its smoke point, which is beneficial for oils with a good fatty acid profile for frying — for example, rapeseed oil or peanut oil.