Popular Science | Eat more oil, eat good oil, double-low rapeseed oil - the healthiest bulk edible oil

Food, oil, salt, sauce, vinegar and tea, oil is a necessity of life. Edible oil (oil) is one of the three major nutrients of the human body (carbohydrates, fats and proteins), an important source of essential fatty acids for the human body, a major component of cell membranes, can provide about 30% of life energy and maintain body temperature, and is a medium for fat-soluble nutrients such as plant sterols, polyphenols, vitamins, and β-carotene. These nutrients are indispensable to the body but cannot be synthesized by the body itself and must be provided by food. They can only be absorbed and utilized by the body when dissolved in oil. Double-low rapeseed oil has the characteristics of "four highs, three lows and one balance", that is, high oleic acid content, high linoleic acid and linolenic acid content, and a reasonable ω-6/ω-3 ratio, high oil-soluble nutrients and low saturated fatty acids, low (no) hazard factors, and low pollutants. It is the most beneficial to human health. Bulk vegetable edible oil.

Figure 1 Important functions of edible oil

1The effects of rapeseed oil's main components on the human body

1.1 Effects of fatty acids on the human body Oils and fats, also known as triglycerides, are composed of one glycerol molecule and three fatty acid molecules. Different types of fatty acids have different effects on human health. From the perspective of classification, fatty acids in edible oils are divided into saturated fatty acids (such as stearic acid, palmitic acid, etc.) and unsaturated fatty acids. Unsaturated fatty acids include monounsaturated fatty acids (such as oleic acid, erucic acid, etc.) and polyunsaturated fatty acids (such as linoleic acid, α-linolenic acid, etc.) (Figure 2). The following are some major fatty acid functions: saturated fatty acids can lead to increased serum cholesterol, triglycerides, etc. Among them, increased serum cholesterol levels are an important cause of atherosclerosis and increase the risk of coronary heart disease; in addition, saturated fatty acids promote cancer cell proliferation and increase the risk of cancer. Oleic acid is easily absorbed by the human body and can reduce the concentration of low-density lipoprotein in human blood to prevent cholesterol from depositing on the blood vessel wall, causing atherosclerosis or vascular sclerosis; in addition, oleic acid promotes wound healing and is beneficial for the treatment of cancer, autoimmune and inflammatory diseases. Linoleic acid (ω-6 fatty acids) can lower blood cholesterol and prevent atherosclerosis; cholesterol must be combined with linoleic acid to be metabolized normally in the body; without linoleic acid, cholesterol will combine with certain saturated fatty acids and deposit on the blood vessel walls, forming atherosclerosis and causing cardiovascular and cerebrovascular diseases. Linolenic acid and its derivatives (EPA, DHA) are involved in the development of the human brain and retina. Linolenic acid is the precursor of DHA and EPA and is an essential fatty acid for the human body. It is closely related to human vision, intelligence and brain power. Studies have shown that ω-3 fatty acids (linolenic acid and its derivatives) have the function of delaying or even preventing the occurrence of Alzheimer's disease; while a lack of ω-3 fatty acids can lead to decreased vision, memory loss, decreased learning ability, mental fatigue, Alzheimer's disease, etc.
Figure 2 Fatty acid categories in oils and fats

1.2 Effects of oil-soluble nutrients on the human body

Oil-soluble nutrients include sterols, fat-soluble vitamins VE, β-carotene, plant polyphenols, etc. Sterols can lower cholesterol and prevent cardiovascular and cerebrovascular diseases; fat-soluble vitamins can regulate blood lipids and delay aging; carotenoids can maintain visual function and improve reproductive function; plant polyphenols have antioxidant and anti-aging effects and improve vascular elasticity.
2 Standards for healthy cooking oil

2.1 Reasonable fatty acid composition and high content of essential fatty acids In general, the fatty acid composition of "good oil" is low in saturated fatty acids, high in oleic acid, and high in linoleic acid and linolenic acid. At the same time, the ratio of linoleic acid (ω-6) and linolenic acid (ω-3) is reasonable. The World Health Organization stipulates that the ratio of linoleic acid to linolenic acid is less than 4:1, which is within the normal nutritional range. A high ratio will weaken the mucosal barrier capacity and increase the risk of obesity, metabolic diseases, cardiovascular and cerebrovascular diseases, mental diseases and brain diseases. It also has adverse effects on joints, bones, eyes and reproductive organs.

2.2 Rich in oil-soluble nutrients Sterols, VE, β-carotene, plant polyphenols, etc. are oil-soluble nutrients that play an important role in human health. When people buy edible oil, they often prefer clear and bright salad oil, which is actually a misunderstanding of healthy oil. As mentioned earlier, oil-soluble nutrients such as plant sterols and polyphenols in edible oil are beneficial to human health, but the oil-soluble nutrients in salad oil are basically lost during the processing. High-quality edible oil is rich in a variety of oil-soluble nutrients.
3. Rapeseed oil is the healthiest edible oil

3.1 The most reasonable fatty acid composition The "double low" of rapeseed refers to the low erucic acid content in rapeseed oil and the low glucosinolate content in rapeseed cake. During the processing of rapeseed, glucosinolates are degraded into toxins such as thiocyanate and isothiocyanate, oxazolidinone and nitrile under the action of mustard enzyme. Rapeseed cake as feed will interfere with the thyroid gland's absorption of iodine and cause goiter in animals. There is a negative correlation between erucic acid and oleic acid in rapeseed oil, with high erucic acid and low oleic acid. Long-term consumption of rapeseed oil with high erucic acid will thicken the human heart envelope and aggravate the occurrence of cardiovascular diseases. At present, China's rapeseed industry has basically achieved double low, and the fatty acid composition of rapeseed oil has undergone revolutionary changes. Double-low rapeseed oil is a functional oil. The content of saturated fatty acids (mainly palmitic acid and stearic acid) in its fatty acids is only about 7%, and the proportion of unsaturated fatty acids reaches more than 90%, of which monounsaturated fatty acid oleic acid accounts for about 63%, polyunsaturated fatty acids linoleic acid accounts for about 20%, and linolenic acid accounts for about 9% (Table 1).

Table 1 Fatty acid composition of double-low rapeseed oil and double-high rapeseed oil (%)

Data published in the Journal of Oil Crops in China in 2016 (Table 2) show that among the major edible oils, palm oil and animal fats and lard have the highest content of saturated fatty acids; the content of beneficial fatty acids oleic acid in rapeseed oil, olive oil, and tea oil is higher than 50%; the content of linoleic acid in sunflower oil, corn oil, soybean oil, cottonseed oil, and safflower oil is relatively high; the content of linolenic acid in rapeseed oil and soybean oil is similar. Looking at the fatty acid composition of different types of edible oils, lard and palm oil, two common oils in China, have too high a content of saturated fatty acids, which is not good for human health. Except for rapeseed oil and olive oil, the oleic acid content of other edible oils is less than 50%; although the oleic acid content of olive oil is high, it lacks ω-3 fatty acids. Rapeseed oil, soybean oil, and sesame oil contain higher linolenic acid (ω-3 fatty acids), but the ω-6/ω-3 (linoleic acid/linolenic acid) ratio in soybean oil is high (>6), exceeding the requirements of the World Health Organization. Therefore, the fatty acid composition of double-low rapeseed oil is the most reasonable, without any shortcomings, and it is the most beneficial bulk edible oil for human health (Table 3).

Table 2 Fatty acid composition of different edible oils (%)

Note: Data from Li Dianrong et al., Chinese Journal of Oil Crops, 2016, 38: 850-854. C18:1 means the fatty acid carbon chain contains 18 carbons and 1 unsaturated bond, and the same applies to the others.
Comparison of fatty acid composition between rapeseed oil and several higher priced vegetable oils

3.2 Rich in oil-soluble nutrients Rapeseed oil is rich in nutrients, among which the content of plant sterols and polyphenols is the highest among edible vegetable oils. The reason why rapeseed oil is more beneficial to lowering low-density lipoprotein than olive oil may be related to the fact that rapeseed oil is rich in sterols. The polyphenol content of rapeseed is 10 to 30 times that of other oil crop seeds. In addition, the content of VE and β-carotene is also high. Using different pressing processes can retain these nutrients to the maximum extent. For example, the functional rapeseed oil produced by low-temperature microwave pressing technology has a plant polyphenol content of more than 30 times that of salad oil, a total sterol content of 2.4 times that of salad oil, a β-carotene content of 4.5 times that of salad oil, and a total vitamin E content of 2.6 times that of salad oil.

3.3 Low hazard factors Rapeseed oil contains low levels of exogenous pollutants such as biological toxins, heavy metals, and plasticizers, and has a low risk of aflatoxin contamination. In addition, rapeseed oil contains low levels of harmful substances such as benzopyrene, pesticide residues, trans fatty acids, and heavy metals. In summary, double-low rapeseed oil has the characteristics of "four highs, three lows, and one balance", including high oleic acid, second-high linoleic acid, relatively high linolenic acid, high oil-soluble nutrients, low saturated fatty acids, low (no) hazard factors, low pollutants, and a reasonable ratio of linoleic acid/linolenic acid. It is the healthiest bulk vegetable edible oil.
About the Author

Zhang Ka, PhD, is an assistant researcher at the Institute of Crop Science, Sichuan Academy of Agricultural Sciences. He graduated from Huazhong Agricultural University and studied under Academician Fu Tingdong and Professor Tu Jinxing during his postgraduate studies. He is currently mainly engaged in the creation of new rapeseed materials, breeding of new varieties, molecular biology, genomics and other research. He has published 4 papers in journals such as Plant Physiology as the first author, presided over 2 Sichuan Youth Fund and Academy Talent Projects, and participated in 7 projects such as the National Key R&D Program and the Provincial Major Project of Biological Breeding.