Definition
LDL belongs to the group of cholesterol. LDL is the abbreviation for Low Density Lipoprotein, which means “low density lipoprotein”. Lipoproteins are substances consisting of lipids (fats) and proteins.
They form a ball in the blood in which various substances can be transported. Inside the sphere, the hydrophobic (i.e. water-insoluble) components of the LDL point to the inside, the hydrophilic (water-soluble) components form the envelope. LDL is mainly needed to transport water-insoluble substances.
Standard values
The standard values for total cholesterol (not only LDL but also HDL) are <5.2 mmol/l, which corresponds to 200 mg/dl. The limit values for LDL depend on the risk profile of the person for coronary heart disease and atherosclerosis (calcification of the vessels). The risk depends on gender, age, cardiovascular disease and many other factors.
If the risk is low, the limit is 4.2 mmol/l (160 mg/dl). For a medium risk the limit shifts to 3.4 mmol/l (130 mg/dl). A high risk exists if coronary heart disease or atherosclerosis is already present. In this case the cholesterol level should be lowered below 2.6 mmol/l (100 mg/dl).
What is LDL needed for?
As a lipoprotein, LDL is ideally suited to transport non-water-soluble (hydrophobic) substances in the blood. For this purpose, LDL forms small transport spheres, which are usually filled with fats or fat-soluble (lipophilic) substances. The main function of LDL is to transport cholesterol, which is produced in the liver, to other regions.
Cholesterol is needed almost everywhere in the body: it forms the basic structure of hormones or bile acids, for example, and is also found in cell membranes. Therefore, it is transported by the LDL into the various tissues, organs and also into vessels. Besides the transport of cholesterol, LDL also has other transport tasks.
The fat-soluble vitamins (vitamin A, vitamin D, vitamin E and vitamin K), which are needed at different places in the body, are also well stored in the ball of LDL. Other fat-soluble substances that are distributed in the body by LDL are phospholipids, fatty acids and so-called triglycerides (also body fats). LDL itself is also produced in the liver, where it can immediately absorb the substances it is transporting. From there it is flushed out into the blood and reaches other body cells. In these cells the LDL-transport particle is broken down, at the same time the ingredients are released and can be further utilized by the respective cells.
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