What Is Cholesterol?

Cholesterol has quite a bad reputation. Much of it is not deserved. Cholesterol is a vital component of all cell membranes. It protects nerve cells and is the backbone for many hormones--among them cortisol, estrogen, progesterone, and testosterone. It is also used to make vitamin D and bile, a substance that helps digest fat.

Unfortunately, too high a concentration of cholesterol in the blood is associated with an increased risk of heart disease. Coronary artery disease affects millions of Americans. High cholesterol is one of many risk factors for developing heart disease.

Where Does Cholesterol Come From?

Most of the cholesterol circulating in your blood is made in the liver from fat metabolism. The rest--about 20 percent--comes from the foods you eat. Dietary cholesterol comes from animal products, such as meat, milk, cheese, and butter. It can also be made in the liver from saturated fat, which is found in animal products, certain types of oils (palm oil, coconut oil), and many snack foods.

What Are the Types of Cholesterol?

Cholesterol and fat are transported through the bloodstream in particles called lipoproteins. Lipoproteins contain different proportions of lipid (fat) and protein molecules:

Chylomicrons--These are the largest lipoproteins. Chylomicrons have the highest content of fat. These lipoproteins carry triglycerides (fat from the foods you eat) from the intestine to body tissues, where they are used for energy or stored as fat.

Very Low Density Lipoproteins (VLDLs)--VLDLs have a little bit more protein than chylomicrons. They carry triglycerides made by the liver to their destination in body tissues.

Low Density Lipoproteins (LDLs)--LDLs are stuffed full of cholesterol. They hold about 2/3 of all the cholesterol in the blood. These particles, called "bad" cholesterol, are partially responsible for forming plaque along blood vessel walls. The more LDLs you have, the greater your risk of getting coronary artery disease--or a heart attack.

High Density Lipoproteins (HDLs)--HDLs are known as "good" cholesterol. They are the protective counterparts to LDLs. HDLs contain a high proportion of protein, and their function is to scour the bloodstream, collecting excess cholesterol and transporting it back to the liver to be recycled or disposed of.

Cholesterol and Heart Disease

Increased levels of cholesterol in the blood can contribute to atherosclerosis. This is the gradual build-up of cholesterol, fat, and fibrous debris along the walls of your arteries. This plaque build-up can accumulate enough to narrow the artery and stiffen the arterial wall. If the plaque is severe enough it can impair blood flow past the blockage.

Part of the plaque can also break off. Or, the plaque can become unstable and rupture. When this occurs, blood is exposed to the inner material of the plaque, which causes a clot to form. This can can form rapidly and completely obstruct an entire artery, or it can be released into the circulation. Once released, clots can travel through the bloodstream through smaller and smaller vessels until they either dissolve or reach a point where they cannot squeeze through, causing a blockage. When this blockage occurs in a coronary artery (one of several arteries that supplies the heart tissue with blood), the result is often a heart attack. If the blockage occurs in a brain artery, a stroke takes place. The extent of the damage depends on the size of the blood vessel that is blocked or the location of the blood vessel.

What Is Your Risk?

A high level of blood cholesterol is associated with an increased risk of heart disease. But, unlike other risk factors for heart disease that you cannot change or modify, such as age, sex, or a family history of heart disease, you can lower a high cholesterol level. That is why it is monitored so closely.

Check the risk factors below to see if they apply to you. The more risk factors you have, the greater your chances of developing heart disease.

Risk Factors You Can't Change

Males

Females after menopause

Family history of heart disease or high cholesterol

Modifiable Risk Factors

High blood pressure

Smoking

Inactive Lifestyle

Obesity

Type 2 diabetes

High Cholesterol

by Christine Perry, MS, RD