Hypercholesterolemia is the term used to refer to a high blood cholesterol level. Cholesterol is a waxy substance that is produced by the liver and is a component of all cells found in the body.
All of the cholesterol a person needs is produced in the liver, but another source is dietary cholesterol, which comes from animal food products such as meat, poultry, dairy, egg yolk and fish. Such foods are rich in saturated fats and
trans fats, substances that can trigger the liver to make an excess of cholesterol and in some cases, this can lead to hypercholesterolemia.
Cholesterol is required for various bodily functions including the synthesis of cell membranes and certain hormones and the production of substances required for fat digestion. However, a cholesterol level that is too high can increase the risk of coronary artery disease.
Excess cholesterol present in the blood forms fatty deposits in the walls of the coronary arteries, the blood vessels that supply the heart with blood. As the cholesterol accumulates, it causes atherosclerotic plaques to form, which narrow and harden the artery walls. This is referred to as atherosclerosis. Eventually, these plaques can block the arteries and limit the amount of oxygen-rich blood that can reach the heart. This increases a person’s risk of angina and heart attack. If the artery that supplies blood flow to the brain (carotid artery) becomes narrowed and hardened, then a person is at an increased risk of suffering a stroke.
There are also inheritable forms of hypercholesterolemia that can cause excess cholesterol to accumulate in other bodily tissues such as the tendons or the under the skin of the eyelids. The most common of these conditions is familial hypercholesterolemia. In most countries, the incidence of this condition is about 1 in 500, but it is more common among certain populations including French Canadians, Finns and Lebanese.
Although a high cholesterol level can be inherited, it is usually the result of a diet high in saturated fat and a low level of physical activity. It can therefore often be prevented through healthy lifestyle choices such as exercising regularly and following a low-fat diet. If diet and exercise do not bring the cholesterol level down, cholesterol lowering medications may be recommended.
Cholesterol is circulated in the blood attached to transport proteins, a combination referred to as lipoproteins. These lipoproteins are classified depending on the type of cholesterol they carry. Low-density lipoprotein (LDL) carries cholesterol from the liver to various parts of the body. If there is an excess of LDL, cholesterol can accumulate in the walls of arteries and lead to atherosclerosis. LDL is therefore sometimes called “bad cholesterol.”
High-density lipoprotein (HDL), on the other hand, carries excess cholesterol away from cells to the liver, where it is broken down and treated as a waste product. This lipoprotein is referred to as “good cholesterol.”
Unhealthy lifestyle choices such as physical inactivity, a high-fat diet and obesity increase the risk of a high LDL level and a low HDL level. Other risk factors include, smoking, diabetes, high blood pressure, and having a family history of stroke or heart disease.
Hypercholesterolemia does not usually present with any symptoms and the only way to check for the condition is to perform a check of the blood cholesterol level, referred to as a lipid profile. This test typically includes a check of the total cholesterol, LDL cholesterol, HDL cholesterol and triglyceride level.
A total cholesterol level of above 200 mg/dL is generally considered high and an HDL of below 40 is generally considered poor. However, whether or not a lipid profile is considered safe or not also depends on whether a person is at risk of or has heart disease.
Patients diagnosed with hypercholesterolemia are advised to modify their diet and engage in regular physical activity. Examples of recommended dietary changes include avoiding foods rich in saturated fat such as cheese, butter, cream and high-fat meats. Saturated fat intake should be restricted to a maximum of 30 grams per day for men and 20 grams per day for women.
If the blood cholesterol level remains high after a few weeks, the patient may be prescribed medication. The drug or drug combination chosen depends on several factors including age, current health, potential side effects and individual risk factors.
Common examples of treatment strategies include the following:
These block a substance required by the liver for cholesterol synthesis, which triggers the liver to acquire cholesterol from the blood. The body may also remove cholesterol from plaques that have formed in the arteries which can improve artery health. Statins:
The liver needs cholesterol to make the bile acids required for digestion. By binding to bile acids, these resins cause the liver to acquire excess cholesterol in order to still produce the acids, which has the effect of lowering the blood cholesterol level. Bile-Acid-Binding Resins:
Since cholesterol is absorbed into the bloodstream from food in the small intestine, inhibitors of this process help to reduce the blood cholesterol level. Cholesterol Absorption Inhibitors:
Edited by Sally Robertson, BSc Further Reading