Unsaturated fatty acid is a kind of fatty acid that constitutes body fat and is necessary for human body. Unsaturated fatty acids are divided into monounsaturated fatty acids and polyunsaturated fatty acids according to the number of double bonds. Among food fats, monounsaturated fatty acid is oleic acid, and polyunsaturated fatty acid is linoleic acid, linolenic acid and arachidonic acid. The human body cannot synthesize linoleic acid and linolenic acid, so it must be supplemented from the diet. According to the position and function of double bonds, polyunsaturated fatty acids are divided into ω-6 series and ω-3 series. Linoleic acid and arachidonic acid belong to ω-6 series, while linolenic acid, DAH and EPA belong to ω-3 series.
I. Physiological functions of unsaturated fatty acids
1. Maintain the relative fluidity of cell membrane and protect the normal physiological function of cells.
2. Esterify cholesterol and reduce blood cholesterol and triglycerides.
3. It is the precursor of prostaglandin and thromboxane synthesized by human body.
4. Reduce blood viscosity and improve blood microcirculation.
5. Improve the activity of brain cells and enhance memory and thinking ability.
6. Most of the fat is stored in human fat cells, and a small part is stored in other human cells such as plasma.
7. Fat can protect the human body, reduce the influence of external factors on important organs, and can be converted into energy.
8. Fat is conducive to the formation of new cells and plays a vital role in maintaining the normal development of the brain and nerve function.
9. Fat is also necessary to carry and help absorb fat-soluble vitamins, such as vitamins A, D, E and K and carotenoids.
Second, the surplus and deficiency of unsaturated fatty acids in diet and health
When the unsaturated fatty acids in the diet are insufficient, the following diseases are easy to occur:
1. Low-density lipoprotein and low-density cholesterol in blood increase, leading to atherosclerosis and cardiovascular and cerebrovascular diseases.
2.ω-3 unsaturated fatty acids are important nutrients in the brain and cranial nerves. Insufficient intake will affect memory and thinking ability, affect the intellectual development of infants, and produce Alzheimer's disease in the elderly.
Too much diet will interfere with the synthesis of growth factors, cytoplasm and lipoprotein, especially too much ω-6 series unsaturated fatty acids will interfere with the utilization of ω-3 unsaturated fatty acids, which is easy to induce tumors.
Three. Recommended daily intake
The content of polyunsaturated fatty acids is an important basis for evaluating the nutritional level of edible oil. Among soybean oil, corn oil and sunflower oil, ω-6 series unsaturated fatty acids are higher, while ω-3 unsaturated fatty acids are higher in linseed oil and perilla oil. Because unsaturated fatty acids are easily oxidized, we should increase the intake of vitamin E when eating. Generally, the ratio of ω-6 to ω-3 should be 4- 10 to 1, and the intake should account for 50%-60% of the total fat intake.
Fourth, the source of food.
1. The calorie density of fat (1g = 9 calories) is twice that of carbohydrate or protein (1g = 4 calories). Although olive oil and rapeseed oil are good for health, they are also high in calories (1 spoon = 120 calories). In addition, many processed foods and fast food are also high in fat, especially saturated fat.
2. Polyunsaturated fats exist in tea oil, olive oil, rapeseed oil, safflower seed oil, sunflower seed oil, corn oil and soybean oil. Medium. Saturated fat exists in animal products, such as butter, cheese, whole milk, ice cream, cream and fat, and some vegetable oils (coconut oil, palm oil and palm kernel oil).
Verbs (short for verb) are important.
All healthy people need to eat a certain amount of fat in their diet to maintain various functions of the human body. Long-term intake of large amounts of fat may cause health hazards. Generally speaking, healthy adults should not consume more than 30% of the total calories from foods with high fat content. Among these 30%, the calorie intake from foods with high saturated fat content should not exceed 10%.