Cholesterol is a term that most people associate with disease. Too much cholesterol, they say, is a bad thing: Those who have it run the risk of diseases from the cardiovascular chapter. But what exactly is this cholesterol, why do people have it if it is bad? What happens if my cholesterol is too high and how can I protect myself from high cholesterol? And what does the cholesterol level have to do with my diet? We provide the answers below.
What is cholesterol?
First of all, cholesterol is a vital substance. It is not only present in the human body, but is widely found throughout the animal kingdom. Cholesterol is a fat molecule that plays an important role in the body as a component of cell walls and as a building block of many hormones.
Function and roles of cholesterol
Cholesterol performs a basic function for the cell, which is the smallest building block of a living being: the substance serves as a “softener” for its membrane. The membrane is a kind of closed bag that surrounds the cell and protects its contents from the outside world. On the one hand, it must be a strong barrier, but on the other hand, it must also be flexible. Cholesterol gives the so-called lipid bilayer that makes up the membrane the soft, pliable properties it needs.
Cholesterol: important for digestion and hormone balance
Cholesterol is also enormously important for our digestion. In the liver, cholesterol is turned into bile acid by chemical modification. This passes from the liver through the bile, where it is stored, and through the bile duct into the intestines. There it is secreted whenever food is consumed. As a “soap,” bile acid is able to dissolve fatty food components, making them accessible to the body. In addition, chemical changes in cholesterol in human glands lead to the production of hormones called steroid hormones, among them estrogen and testosterone.
Origin of the multi-talent cholesterol
Where do humans get this vital little molecule? Once 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 food, but is also able to produce it itself. The little cholesterol factory in the body is quite industrious: one to two grams of the substance in a day is a proud achievement. Three quarters of the cholesterol is produced by the body itself, while one quarter is ingested through food. However, the body’s own production would be sufficient even if people did not take in any additional cholesterol through food.
How is cholesterol transported in the body?
So humans need cholesterol, but why does high cholesterol now so often doom them? The basic reason lies in the chemical properties of the building block: cholesterol is fat-soluble, but not water-soluble. Just like olive oil in pasta water, it would therefore not dissolve in the blood, but form small fat beads and adhere to the walls of the blood vessels. So basically, cholesterol is a “dangerous good” that is difficult to transport. Nature has solved this problem by means of a special transport system: certain transporters, known as lipoproteins, bind the body fats, of which cholesterol is one, transport them with the bloodstream, and unload them at their destinations without causing complications due to the insolubility of the fats.
LDL and HDL – the “bad” and the “good” cholesterol.
So how harmful is cholesterol actually? This question is not so easy to answer, but requires a more in-depth look. This is because there are not only different transporters for the various types of body fats (which, in addition to cholesterol, include primarily the so-called triglycerides), but also different ones for different routes in each case. Two of these transporters have gained general notoriety: the HDL (high density lipoprotein) and the LDL (low density lipoprotein). The former is also known as the “good” lipoprotein, the latter as the “bad” lipoprotein.
The difference between HDL and LDL
But where do these ratings come from?First of all, the two transporters differ in their tasks: The LDLs supply the cells with cholesterol from the liver, while the HDLs absorb excess cholesterol and transport it to the liver. There it is converted into bile acid and (at least partially) excreted with food via the intestines. HDL therefore in principle has a “cholesterol-lowering” effect. Nowadays, more importance is attached to the ratio of both types of cholesterol in the blood than to total cholesterol. We explain the consequences of an unfavorable HDL/LDL ratio on the next page.
