Cholesterol is a white-yellowish substance similar to fats. Triglycerides are molecules, built of three fatty acids bound on glycerol. All foods of animal origin contain cholesterol, while there is no cholesterol in foods of plant origin. It is the basic constituent of all the cells in our body, and sexual and adrenal hormones are formed from it, as well as vitamin D and gall acids. Since we usually do not have problems with the lack of it, a lower cholesterol level is generally more favourable. A desired general cholesterol level is less than 5 mmol/L, but even more important is the ratio between the bad LDL and the good HDL cholesterol, which should not be lower than 4:1, or for genetically and environmentally more challenged people, 3:1. It is true that 80 percent of cholesterol is produced by the body, while the cholesterol from food represents 20 percent of the entire amount of cholesterol. In healthy people, with the intake of cholesterol with food, its production in the body usually decreases. In people with an unfavorable genetic makeup this regulation is not optimal, and it can cause an increase of LDL cholesterol as well as the level of triglycerides.
The cholesterol and triglyceride metabolism is quite complicated. They are water insoluble molecules. After ingestion they bind with substances called lipoproteins in the intestinal villi in order to enter the blood stream. In the meantime cholesterol, which is produced by the body in the liver, binds with particles known as VLDL, and also enters the blood stream. From the VLDL complexes, free fatty acids start to detach and enter fat cells where they are transformed back into triglycerides. This way, we get particles, known as IDL, which further lose triglycerides and we get LDL. In everyday life, we normally mention only LDL and HDL. LDL particles contain few triglycerides and are rich in esterified cholesterol (cholesterol bound with fatty acids) and they represent a huge container of cholesterol for the synthesis of steroids, membranes and gall acids. LDL particles transport up to two thirds of cholesterol, known also as harmful cholesterol, around the body, even though it is not necessary for the optimal functioning of the body. They transport it from liver to other parts of the body. HDL particles, however, do just the opposite. They transport the cholesterol in the opposite direction; they eliminate it from the blood stream and return it to the liver, where a greater part of it is excreted in the form of gall acids. The majority of it is again absorbed into the liver and then into the blood.
This process is called "enterohepatic circulation". HDL, therefore, protects the cells of the vascular wall, inhibits the oxidation of LDL cholesterol and prevents clumping of blood platelets – thrombocytes, which accumulate at the site of a damaged vascular wall. Because of this function, it has acquired names such as good, beneficial and protective cholesterol. If the LDL cholesterol concentration overly increases or the HDL cholesterol concentration overly decreases, we risk cardiovascular and coronary disease, such as angina pectoris, heart attack, brain stroke, leg artery disease, etc. The problem is also the oxidation of LDL cholesterol which is encouraged by bad habits, which can lead to cardiovascular disease. Hence it is crucial for our health to pay attention to our diet, exercise and do not succumb to bad habits such as alcohol drinking and smoking.