It is often said that one should consume different types of fatty acids in a balanced way, which is why we are advised to rotate our cooking oils. However, few people know exactly how to do this. Is it as simple as switching brands or names?
There are many types of natural oils. Besides flavor and texture, the main nutritional difference lies in the varying proportions of their fatty acids. Based on their chemical structure, these fatty acids can be broadly classified into three categories: saturated, monounsaturated, and polyunsaturated. Polyunsaturated fatty acids are further divided into two types: the Omega-3 series and the Omega-6 series. The primary components of the Omega-3 series are ALA, DHA, and EPA. The primary component of the Omega-6 series is linoleic acid.
First, many oils, despite having different names, have very similar fatty acid compositions. For example, soybean oil, corn oil, and sunflower oil are similar; peanut oil and rice bran oil are similar; tea seed oil, almond oil, and olive oil are similar; and flaxseed oil and perilla oil are similar. Therefore, when rotating oils, one should switch between varieties with different fatty acid profiles, such as alternating between sunflower oil and peanut oil, or between tea seed oil and flaxseed oil.
Second, consider the cooking temperature. Generally, polyunsaturated fatty acids are less heat-stable, making oils very high in Omega-6 fatty acids unsuitable for stir-frying.
Oils high in monounsaturated fatty acids are: tea seed oil (over 75% oleic acid), olive oil, almond oil, and macadamia oil (over 70% oleic acid), canola oil (also known as rapeseed oil, over 60% oleic acid), and peanut oil and sesame oil (about 40% oleic acid). Poultry fats (like chicken and duck fat) and lard also contain over 40% monounsaturated fatty acids.
Few oils are rich in Omega-3 fatty acids. They are: flaxseed oil, hemp seed oil, perilla oil, and fish oil. Oils that are high in Omega-6 fatty acids while containing small amounts of Omega-3 fatty acids include: evening primrose oil, soybean oil, and pine nut oil.
It is somewhat concerning that Chinese cooking uses so much soybean oil, corn oil, and sunflower oil. A large amount of Omega-6 fatty acids can promote inflammatory responses, and its tendency to oxidize is a major drawback. Recent research has shown that a high proportion of dietary linoleic acid may increase the risk of coronary heart disease, possibly due to its oxidation. Therefore, for Chinese people, relatively ideal cooking oils for daily use would be tea seed oil, refined olive oil, peanut oil, rice bran oil, and canola oil.