Cholesterol is a word that most people associate with illnesses. Too much cholesterol, one knows, is something bad: whoever has it, is in danger of getting diseases from the chapter cardiovascular system. But what exactly is this cholesterol, why does man have it when it is so bad, what happens if I have too much of it and how can I protect myself from it?
A basic building block for many important functions
First of all, cholesterol is a vital substance. It is not only present in the human body, but is found widely throughout the animal kingdom. He fulfills a basic function for the cell, which is the smallest building block of a living thing: cholesterol serves as a "softener" of their membrane. The membrane is a kind of closed bag that surrounds the cell and protects its contents from the outside world. It must be a strong barrier, but it must also be flexible. The so-called lipid bilayer, which makes up the membrane, would be a brittle, fragile structure without cholesterol. Only the small molecule gives it the soft, supple properties it needs.
In fact, in animals living in colder conditions, there is also a higher cholesterol content in the cell membrane: at lower temperatures, more "plasticizer" is needed. Thus, cholesterol is a basic building block of life. And since it is so universal, Mother Nature has entrusted the small "polycyclic aliphatic alcohol" that the chemist would classify with other tasks: in the liver, bile acid is made from the substance by chemical modification, which makes digestion easier for humans. Because the bile acids pass from the liver through the bile, where they are stored, and through the bile duct into the intestine, where they are always released when you bring food to you.
As a "soap" they are able to dissolve the fatty nutrients and make them accessible to the body. In addition, chemical changes in cholesterol in human glands lead to the production of hormones, the so-called steroid hormones, among them estrogen and testosterone.
Where does the little all-rounder come from?
From where does man get the vital little molecule? Again, the great importance of cholesterol is reflected in its many uses: it is so important for life, that the body can not only absorb this building block from the food, but is also able to produce it himself. And the small cholesterol factory in the body is quite diligent: one to two grams of the substance in one day is a proud achievement. And this production is actually sufficient to meet the need, even if humans would not feed cholesterol at all!
And why is it harmful?
So far so good. Man needs cholesterol, why is it so often fatal to him now? The fundamental reason for this lies in the chemical properties of the building block: it is fat-soluble, but not water-soluble. Like the olive oil in pasta water, it would not dissolve in the blood, but form small fat pearls and attach themselves to the vessel walls. Basically, cholesterol is a "dangerous good" that is difficult to transport.
Fortunately, nature has solved this problem through a special transport system: it has founded a kind of taxi company for all body fat. These "taxis" take the body fats, which include cholesterol, in certain places, transport them with the bloodstream and reload them at their destinations, without causing complications due to the insolubility of the fats.
The taxis are special proteins that are able to bind the fats and pack them in such a way that they become soluble in the water (and therefore also in the blood). The loaded taxis are called "lipoproteins" because they consist of protein and fats (lipids).
Special taxis for special tasks: the "bad" and the "good" cholesterol
Now, not only for the various types of body fats (which include cholesterol, especially the so-called triglycerides) different taxis, but also each other for different routes. Two of these taxis, despite their peculiar names, have become well-known: HDL (high-density lipoprotein) and LDL (low-density lipoprotein). The former is also called "good", the second also called "bad" lipoprotein. Where do these ratings come from?
First of all, both "taxis" differ in their tasks: the LDLs supply the cells with cholesterol, they transport this to the cells, while the HDLs absorb excess cholesterol and transport it to the liver. There it is converted into bile acid and (at least partially) eliminated with the food through the intestine. So HDL has a "cholesterol-lowering" effect in principle. Nevertheless, both forms appear in the total cholesterol measurement of the blood: but who has a lot of HDL and low LDL lives still healthier than if it were the other way around. Therefore, more importance is attached today to the ratio of the two cholesterol types in the blood than to the total cholesterol.