What is cholesterol?
CHOLESTEROL is a waxy substance that is widely distributed in tissues throughout the body in the form of free cholesterol and cholesterol esters, a quarter of which are distributed in brain and nerve tissue.
It plays an important physiological function in the human body and is a main indicator of blood lipid tests. Usually, the concentration of cholesterol in the blood is less than 5.72 mmol/L. High levels of cholesterol can increase your risk of heart disease.
There are two types of cholesterol, based on what the lipoprotein carries: low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C). With high levels of LDL-C, it will increase the risk of heart disease. HDL-C has a role in keeping cardiovascular health.
Where does cholesterol come from?
Cholesterol is mainly produced by the liver and can also be obtained through diet. The liver is the main organ producing about 80 percent of the cholesterol, which can provide enough cholesterol to meet the needs of the human body. The other 20 percent of the cholesterol in the human body is affected by the foods you eat. Some foods contain high levels of cholesterol, such as eggs, fatty meat, fish eggs, animal offal, butter, lard, fresh cream, high-fat ice cream, etc.
How does cholesterol move around the body？
Cholesterol is not soluble in the blood, so it is carried through your blood, attached to proteins. The main modes of cholesterol transport include low-density lipoprotein cholesterol (LDL-C) and High-density lipoprotein cholesterol (HDL-C). LDL-C transports cholesterol from the liver to other cells. HDL-C retrieves excess cholesterol from tissues and arterial blood vessels and transports it back to the liver for metabolism and excretion.
What is the function of LDL-C and HDL-C?
LDL cholesterol is sometimes called ‘bad cholesterol’. With high levels of LDL cholesterol, it builds up in the arteries. The build-up of cholesterol causes lumps of hard fat called plaque to form on the artery walls, which will increase the risk of heart disease. These can break off, block the artery, and cause heart attacks and strokes. Thus, it is very essential to prevent heart disease by controlling the level of LDL-C.
HDL cholesterol is the ‘good’ cholesterol. It works like a cleaner, carrying LDL cholesterol out of the arteries to your liver, where it is broken down and used by the body. HDL-C has the function of anti-inflammation, antioxidant and anti-blood clog, reducing the risk of atherosclerosis.
Cholesterol in the liver will be converted into bile acids to help digest fatty foods. Some are changing into hormones and vitamin D3. Some can be excreted directly from the body.
In the next issue, I will tell you more about cholesterol. Stay tuned!
Source: China Medical Team ( NRH)
（Translated by HUANG BAILIN, International Office, Guizhou Medical University）
