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Surprisingly I don’t know! Knowledge of healthy oils

For health, it is necessary to ingest good quality oil, but many people are concerned about consuming too much. What kind of oil is good for the body? We asked Professor Hiroyoshi Inoue, Department of Chemistry, Keio University School of Medicine, about the types of oils, how they work, and how to use them effectively.

Role of oil in the body

Oil (lipid) is one of the energy-producing nutrients (three major nutrients) necessary for the body, along with proteins and carbohydrates. However, protein and carbohydrates are about 4 kcal per gram, whereas fat is about 9 kcal per gram. Because of the high-calorie content and the risk of obesity and lifestyle-related diseases, many people think that it is better to refrain from consuming oil.

The high calorie content means that it is an efficient source of energy for your body. In addition, oil has the important function of “keeping cells and blood vessels healthy”. The cell membrane that covers the cells in the human body is made of lipids called “phospholipids” and “cholesterol.” Lipid intake is necessary for metabolism to maintain a healthy state of cell membranes.

In addition, oil also works to keep blood vessels strong. Blood vessels, which are the passages of blood, repeatedly expand and contract due to fluctuations in blood flow, and are constantly subjected to a load (blood pressure). In order to maintain healthy blood vessels, it is important to maintain the strength to withstand blood pressure and the suppleness to fend off abrasion caused by blood flow, and oil is necessary for this. Without oil, the blood vessels would not be able to withstand the pressure and would burst easily.

Focus on unsaturated fatty acids (omega 3, 6, 9)

There are many types of oils, each with slightly different effects on the body. It is essential for health management to know these differences and take them well.

The function of oil is classified by “fatty acid” which is the main component of oil. They can be roughly divided into two types: saturated fatty acids and unsaturated fatty acids.

Saturated fatty acids, also known as “straight-chain fatty acids,” are fatty acids in which the molecules are arranged in a straight line like a chain. Butter and lard are typical examples, and they solidify white at room temperature. Saturated fatty acids act as an energy source to move the body. In addition to being ingested from food, it can also be synthesized in the body, so excess intake is stored as fat. Therefore, it has been pointed out that it is likely to cause obesity and cardiovascular diseases.

On the other hand, unsaturated fatty acids have a bent molecular structure rather than a straight one. It is a liquid at room temperature, and in addition to being a source of energy, it acts as a component of the body and a substance that contributes to the functioning of the brain. Typical fatty acids are omega 3, omega 6 and omega 9. Omega 3 and omega 6 cannot be produced by the body.

●Omega 3 (n-3 fatty acid)

α-Linolenic acid: It is abundantly contained in perilla oil and linseed oil, and is said to have the effect of lowering triglyceride levels in the blood *1 .

EPA (eicosapentaenoic acid): Contains a large amount in the oil of blue fish, etc., and is said to have the effect of making the blood smooth and preventing blood clots.

DHA (docosahexaenoic acid): Contained in large amounts in blue fish oil, it is said to be related to the development of the brain and nerves *2 .

●Omega 6 (n-6 fatty acid)

Linoleic acid: Contained in large amounts in general vegetable oils such as salad oil, sesame oil, and soybean oil, it is said to have the effect of lowering blood cholesterol levels *3 .

● Omega 9 (n-9 fatty acid)

Oleic acid: Contained in large amounts in olive oil and high oleic type oil (oil extracted from raw materials bred to contain abundant oleic acid. Sunflower oil and safflower oil are commercially available). effect of suppressing bad cholesterol * 4 .

*1: Am J Clin Nutr. 2003 Dec;78(6):1098-102.

*2: Omega-3 Fatty Acids. NIH (National Institute of Health) Office of Dietary Supplements

*3: Cochrane Database System Rev. 2018 Jul 18;7(7):CD011094.

*4: Ministry of Health, Labor and Welfare e-Healthnet “Unsaturated Fatty Acids”

Unsaturated fatty acids that create flexible blood vessels

Omega 3, omega 6, and omega 9 are all unsaturated fatty acids and have a bent molecular structure, but the number of bent points is different. Omega 3 has 3 bends, Omega 6 has 2 bends and Omega 9 has 1 bend. Bent areas are weaker but more flexible. It is an image like a spring that can be made by bending a wire. Omega-3s, which have the most bends, have the most flexible structure.

Due to their structure, unsaturated fatty acids may be beneficial for vascular health. The phospholipids and cholesterol that make up the walls of blood vessels have straight molecules, so they strengthen the walls of blood vessels, but they are not flexible. However, unsaturated fatty acids such as omega-3 increase the flexibility of blood vessels, so arteriosclerosis is less likely to occur and blood pressure can be expected to decrease.

<Omega 3 reduces the load on blood vessel walls due to blood flow>

– Cholesterol has a linear structure that serves to strengthen the walls of blood vessels but is inflexible

・Omega 3 has a bent structure, so it acts like a cushion and increases the flexibility of the blood vessel wall.

In addition, when the blood vessels soften, the blood vessels expand, the blood flow increases, and nutrients and oxygen can be distributed throughout the body . has a positive effect on brain function. For example, it is expected that depression will be less likely to occur by increasing the secretion of dopamine, which is related to pleasure and motivation *5 .

Even so, if you only ingest omega-3, the strength of the blood vessels maintained by saturated fatty acids will weaken, causing another adverse effect. It is important to have a well-balanced intake of various oils.

*5: J Clin Med 2016 Aug; 5(8): 67. Published online 2016 Jul 27. doi: 10.3390/jcm5080067

Oil is conscious of omega 3 and well-balanced

Modern diets tend to consume too much fat. This is because bread, confectionery, and instant processed foods contain a lot of lipids. The standard for fat intake is 20 to 30% of total energy intake, but 40% of people consume more than 30% of their energy from fat. At this time, the main intake is saturated fatty acids and cheap and easy-to-use omega-6 oils. Omega 6 is necessary for the body because it is a raw material for cytokines, which are substances related to immunity, but if you take too much, you will have an excessive immune response, which is likely to cause hay fever and food allergies. There is also a report that reducing omega-6 oils has improved allergy symptoms *6 .

Also, I want to be conscious of taking omega 3 every day. About one teaspoon of perilla oil or linseed oil per day is enough. Omega 3 and omega 6 are “essential fatty acids” that are necessary for the functioning of the body’s tissues, but they cannot be produced by the body, so they must be ingested from foods. Omega 6 can be sufficiently taken in with a normal diet, but with regard to omega 3, the habit of eating blue fish has decreased recently, so if you are not conscious, you will lose the opportunity to take it.

Omega 3 is weak against light and heat and is easily oxidized, so buy it in a small bottle and use it up as soon as possible. It is not suitable for heat cooking such as frying or stir-frying. it for dressing, or to add richness to cold tofu or somen noodles. Omega-3 supplements are also sold, but it is recommended to take it with meals as oil. In the case of supplements, they are ingested as EPA and DHA, but the excess is excreted outside the body because it cannot be used up. However, when ingested as an oil, it can be temporarily stored in the liver and converted to EPA and DHA when needed.

Oil is essential for health, but the roles and actions differ depending on the type. Know the characteristics of each and try to take them in a well-balanced manner.

*6: Curr Pharm Des 2014;20(6):946-53.

Supervisor profile
Dr. Hiroyoshi Inoue (Professor, Department of Chemistry, Keio University School of Medicine)

[Profile of Professor Hiroyoshi Inoue]

Born in Fukuoka Prefecture in 1961. In 1989, completed the doctoral course at the Graduate School of Science, Kyushu University. After working as an assistant in the Department of Physiology, Yamaguchi University School of Medicine, and as a professor in the Radioisotope Facility, Kurume University School of Medicine, he has been a professor in the Department of Chemistry, Faculty of Medicine, Keio University since 2008. He is a director of the Japanese Society of Anti-Aging Medicine and a councilor of the Japanese Physiological Society. He is a doctor of medicine, doctor of science. He has written many books, including “Body Good Oils: Oil Textbook for Health and Beauty” (Keio University Press), “Healthy Oils from Zero Knowledge” (Gentosha).


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