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Cholesterol is an essential raw material for our bodies. For example, cholesterol is needed to make certain hormones and it’s an important building block for cell walls. But too much cholesterol in the blood can increase the risk of cardiovascular disease.
Cholesterol is needed by every cell in the human body. Your body produces most of what it needs in the liver. Only a small amount comes from our diet. The bloodstream transports cholesterol from the liver to the other organs and tissues in the body. Excess cholesterol is carried back to the liver in the blood.
Although cholesterol is often referred to as a “blood fat,” chemically speaking that is not quite correct. But, like fats, cholesterol does not dissolve in water (or blood), so our bodies need a special system to transport it. Cholesterol is packed into tiny parcels in the liver. The parcels are made up of cholesterol, proteins, fats (lipids) and other things in our blood. They can be transported through our bodies in the bloodstream. Because they are mainly made up of lipids and proteins, the parcels are called “lipoproteins.” There are two different groups of lipoproteins, which differ in how densely they are packed:
- LDL cholesterol: “LDL” stands for “low-density lipoprotein.” This type of parcel transports cholesterol from the liver to the rest of the body. High levels of LDL cholesterol are associated with a higher risk of cardiovascular disease, which is why it’s sometimes referred to as “bad” cholesterol.
- HDL cholesterol: “HDL” stands for “high-density lipoprotein.” This type of parcel transports cholesterol back to the liver from the body’s organs and tissues. According to what doctors know now, high HDL cholesterol levels are probably associated with a lower risk of cardiovascular disease. That is why HDL cholesterol is sometimes also called "good" cholesterol.
High cholesterol levels increase the risk of arteriosclerosis
Arteriosclerosis is the medical term for the arteries hardening, thickening and narrowing. It develops over a very long time. Too much cholesterol in the blood can be a factor.
People used to think that excess cholesterol was deposited in blood vessels like scale in a pipe. But that has turned out not to be true. Depending on their age and lifestyle, most people have small inflammations in the walls of their blood vessels. These can develop in different ways. In people who have high LDL cholesterol, the phagocytes (scavenger cells) in blood “eat” more cholesterol particles. This increases the likelihood of cholesterol sticking to the blood vessel wall.
Inflammations can also weaken the blood vessel wall, which might then tear. If blood suddenly comes into contact with the cholesterol-rich deposits as a result, a blood clot might form. That is because our bodies try to seal the wound in the blood vessel wall, just like when scabs form if you cut your skin.
If this happens, the consequences will depend on various things, including how big the blood clot is. A big clot can completely block the blood vessel, causing a heart attack or stroke. But the blood clots that form are often only small – they fix the damage in the blood vessel wall and do not have any noticeable consequences. Then the cut heals on its own. This can lead to scarring and calcification of the blood vessel wall, which can gradually make the blood vessel narrower without blocking it completely.
Inflammations can develop in any artery in the body. They are particularly dangerous in the large arteries that carry blood to the brain and heart. Narrow coronary blood vessels can cause chest pain (pectoral angina) during physical strain. If a coronary blood vessel becomes blocked, blood will no longer flow to part of the heart muscle, which might result in a heart attack. If a blood vessel in the brain becomes blocked, it might lead to a stroke.
Increased LDL cholesterol levels increase the likelihood of arteriosclerosis and possible complications. But there are many other risk factors for arteriosclerosis, including high blood pressure, diabetes, severe obesity, and smoking. Certain diseases can also make arteriosclerosis more likely.
Cholesterol levels alone do not tell us much about how effective treatments are
A high LDL cholesterol level is a recognized risk factor for cardiovascular disease. Cholesterol levels can help get an idea of someone’s individual risk. But that does not mean that everything that can improve cholesterol levels, or claims to do so, is automatically good for your health.
For example, one medication called torcetrapib was shown to be very effective at increasing “good” cholesterol levels and reducing “bad” cholesterol levels. But when the manufacturer did a study involving 15,000 people to see whether torcetrapib also prevented cardiovascular disease, the opposite was found to be true: it actually increased the risk of cardiovascular disease. So it was never approved as a medicine.
This example makes it clearer why it’s so important to take factors other than cholesterol levels into account when assessing the advantages and disadvantages of treatments. There is a lot of advice out there about what to do about high cholesterol, and many treatments are available. But only some of them have been reliably proven to prevent serious health problems, such as heart attacks, and increase life expectancy.
Sources
- Barter PJ, Caulfield M, Eriksson M et al. Effects of torcetrapib in patients at high risk for coronary events. N Engl J Med 2007; 357(21): 2109-2122.
- Kasper DL, Fauci AS, Hauser SL et al. Harrison's Principles of Internal Medicine. New York: McGraw-Hill; 2015.
- Parhofer KG. The Treatment of Disorders of Lipid Metabolism. Dtsch Arztebl Int 2016; 113(15): 261-268.
- Pschyrembel Online. 2022.
IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.
Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. informedhealth.org can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.
Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.
- In brief: What is cholesterol and how does arteriosclerosis develop? - InformedH...In brief: What is cholesterol and how does arteriosclerosis develop? - InformedHealth.org
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