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Lowering Your Cholesterol
Heart Attack Prevention Series

Cholesterol Drugs Slideshow

Medical Author Revision: Dennis Lee, M.D., Daniel Kulick, M.D.
Medical Editor: William C. Shiel Jr., MD, FACP, FACR

Additional Heart Attack Prevention Series Information (related articles)

Mr. D.T.'s Story - There Is Hope

Medical Author: Dennis Lee, M.D.

I am sure many of you have been reminded by doctors, nurses, and public health officials to lose excess weight, quit smoking cigarettes, exercise regularly, and eat less saturated fat and sweets. Here is a real life example of how effective these measures can be.

Mr. DT is a healthy and active 50-year-old man. He exercises 6 days a week. He does not smoke cigarettes. He tries to hold down fat and cholesterol intake; he only cheats on weekends and holidays. He is slightly overweight (only 12 pounds heavier than ideal body weight). His mild high blood pressure has been well controlled with an oral medication called an ACE inhibitor. There is no family history of any heart disease.

Last week, he asked his doctor for a complete blood panel that includes cholesterol and triglyceride levels, since he has not had one for more than a year. The nurse who drew his blood first noticed there was something wrong; Mr. DT's serum was abnormally discolored. Before performing blood chemistry measurements, she had to spin the blood sample in a centrifuge to separate the red and white blood cells from the serum. Normal serum is clear yellow in color. But Mr. DT's serum was pink and milky. Milky serum indicates excess chylomicrons (protein complexes that contain high amounts of triglycerides and cholesterol).

Read the rest of Mr. DTs story »

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What is cholesterol?

Cholesterol is a fatty substance (a lipid) that is an important part of the outer lining (membrane) of cells in the body of animals. Cholesterol is also found in the blood circulation of humans. The cholesterol in a person's blood originates from two major sources; dietary intake and liver production. Dietary cholesterol comes mainly from meat, poultry, fish, and dairy products. Organ meats, such as liver, are especially high in cholesterol content, while foods of plant origin contain no cholesterol. After a meal, cholesterol is absorbed by the intestines into the blood circulation and is then packaged inside a protein coat. This cholesterol-protein coat complex is called a chylomicron.

The liver is capable of removing cholesterol from the blood circulation as well as manufacturing cholesterol and secreting cholesterol into the blood circulation. After a meal, the liver removes chylomicrons from the blood circulation. In between meals, the liver manufactures and secretes cholesterol back into the blood circulation.

What are LDL and HDL cholesterol?

LDL cholesterol is called "bad" cholesterol, because elevated levels of LDL cholesterol are associated with an increased risk of coronary heart disease. LDL lipoprotein deposits cholesterol on the artery walls, causing the formation of a hard, thick substance called cholesterol plaque. Over time, cholesterol plaque causes thickening of the artery walls and narrowing of the arteries, a process called atherosclerosis.

HDL cholesterol is called the "good cholesterol" because HDL cholesterol particles prevent atherosclerosis by extracting cholesterol from the artery walls and disposing of them through the liver. Thus, high levels of LDL cholesterol and low levels of HDL cholesterol (high LDL/HDL ratios) are risk factors for atherosclerosis, while low levels of LDL cholesterol and high level of HDL cholesterol (low LDL/HDL ratios) are desirable.

Total cholesterol is the sum of LDL (low density) cholesterol, HDL (high density) cholesterol, VLDL (very low density) cholesterol, and IDL (intermediate density) cholesterol.

What determines the level of LDL cholesterol in the blood?

The liver not only manufactures and secretes LDL cholesterol into the blood; it also removes LDL cholesterol from the blood. A high number of active LDL receptors on the liver surfaces is associated with the rapid removal of LDL cholesterol from the blood and low blood LDL cholesterol levels. A deficiency of LDL receptors is associated with high LDL cholesterol blood levels.

Both heredity and diet have a significant influence on a person's LDL, HDL and total cholesterol levels. For example, familial hypercholesterolemia (FH) is a common inherited disorder whose victims have a diminished number or nonexistent LDL receptors on the surface of liver cells. People with this disorder also tend to develop atherosclerosis and heart attacks during early adulthood.

Diets that are high in saturated fats and cholesterol raise the levels of LDL cholesterol in the blood. Fats are classified as saturated or unsaturated (according to their chemical structure). Saturated fats are derived primarily from meat and dairy products and can raise blood cholesterol levels. Some vegetable oils made from coconut, palm, and cocoa are also high in saturated fats.

Does lowering LDL cholesterol prevent heart attacks and strokes?

Lowering LDL cholesterol is currently the primary focus in preventing atherosclerosis and heart attacks. Most doctors now believe that the benefits of lowering LDL cholesterol include:

Reducing or stopping the formation of new cholesterol plaques on the artery walls;
Reducing existing cholesterol plaques on the artery walls;
Widening narrowed arteries;
Preventing the rupture of cholesterol plaques, which initiates blood clot formation;
Decreasing the risk of heart attacks; and
Decreasing the risk of strokes. The same measures that retard atherosclerosis in coronary arteries also benefit the carotid and cerebral arteries (arteries that deliver blood to the brain).