The normal growth and development of teenagers need three nutrients, namely protein, fat and carbohydrate, among which lipids mainly include triglycerides, phospholipids and sterols, while cholesterol is one of the sterols and the most important one. It is an important part of cell membrane and plays an important role in maintaining normal cell function. Cholesterol is an indispensable raw material for maintaining normal metabolism, an important substance for anti-aging and prolonging life, and also an important raw material for various hormones in the body, such as steroid hormones, vitamin D, bile acids and so on. It can be said that cells can not do without cholesterol, and the body can not do without cholesterol. Once there is no cholesterol in the human body, not only health and longevity are impossible to talk about, but even the normal physiological metabolism and life process of the human body cannot be maintained.

Cholesterol can be divided into good and bad. Cholesterol mainly exists in animal foods, especially in the viscera and brains of animals, while the content in fish and milk is low. For example, every 100g of pig brain, sheep brain, yolk and egg (including egg white) contains 257 1mg, 2004mg, 2850mg and 585mg of cholesterol respectively. There are two main sources of cholesterol in the human body: one is endogenous, that is, it is synthesized by the liver, accounting for about 70% of total cholesterol; The other part is exogenous, that is, cholesterol from food, accounting for about 30%. If the intake of cholesterol in food is insufficient for a long time, the body will step up its synthesis to meet the needs of the human body.

Cholesterol is divided into high-density cholesterol and low-density cholesterol. The former has a protective effect on the cardiovascular system, which is usually called "good cholesterol". The higher the latter, the higher the risk of coronary heart disease, which is usually called "bad cholesterol". The cholesterol content in blood is between 0/40 ~199 mg per unit, which is a relatively normal cholesterol level. The more fat, the higher the cholesterol absorption.

Cholesterol in food is not completely absorbed by human body, and the amount of cholesterol absorbed mainly depends on the following factors:

First, when bile acid is deficient in the body, the absorption of cholesterol will be significantly reduced. The fat in food can promote the secretion of bile, and the decomposition products of fat are also beneficial to the absorption of cholesterol. Therefore, the more fat in food, the more cholesterol can be absorbed.

Second, the absorption rate of cholesterol in the body decreases with the increase of cholesterol content in food. The higher the cholesterol content in food, the lower the absorption rate of human body, but when the cholesterol content in food is high, the absolute absorption of human body will increase.

Third, saturated fatty acids contribute to the increase of cholesterol, while unsaturated fatty acids contribute to the decrease of cholesterol.

Fourth, some ingredients in food affect the absorption of cholesterol. For example, sitosterol can reduce the absorption of cholesterol, and dietary fiber in food also has this function. Too high or too low cholesterol is harmful to health.

If the cholesterol in human blood is too high, it will cause atherosclerosis, which is the main risk factor of coronary heart disease, myocardial infarction and stroke. But if the cholesterol in the blood is too low, it will also cause damage to the body.

Cholesterol is an essential "building material" for human body, which supports the structure and morphology of all cells in the body. Cholesterol-deficient cells are like a box of jelly with holes. When they come into contact with emotional regulation chemicals in the brain, cells with poor density can't respond correctly. The working mechanism of cells is similar to locks and keys. Cells are locks, and nerve transmission is the key. If the cell structure is not good, it may be difficult to unlock the key and activate the cell, so people's mood is extremely unstable.

Moreover, when human cholesterol is insufficient, the cell membrane tissue will be destroyed, and the function and activity of phagocytosis of abnormal cells by white blood cells will be weakened, so that abnormal cells, including cancer cells, cannot be effectively identified, killed and swallowed, and the human body will suffer from diseases such as cancer. The data shows that people with low cholesterol levels in the body are three times more likely to develop colon cancer than those with normal cholesterol levels, and the prevalence of other cancers has also greatly increased. It is advisable to take 300 mg of cholesterol every day.

Human cholesterol is by no means dispensable, and it must be kept at a certain level to make the physiological process go smoothly. So how much should the human body consume every day? Dr. Liang suggested that the daily intake of cholesterol should not exceed 300 mg, which is about equivalent to the amount of an egg.