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What Is “Good” Cholesterol and “Bad” Cholesterol?

Your liver creates cholesterol from nutrients in your diet and your body cannot function without that cholesterol. Because cholesterol is known to increase risk of certain diseases, many people are confused when they hear that a healthy body needs cholesterol. Here’s the low-down on cholesterol.

A lipoprotein is a fat and protein particle that carries cholesterol through your blood. Your body makes four types of lipoproteins:

  • Chylomicrons: Lipoprotein is born as a chylomicron, made in your intestinal cells from protein and triglycerides (fats). After 12 hours of traveling through your blood, a chylomicron looses almost all of its fats. When it reaches your liver, the only thing left is protein.

  • Very low-density lipoproteins (VLDLs): These fatty lipoproteins carry cholesterol into blood vessels, where it can form deposits, or plaques.

  • Low-density lipoproteins (LDLs): LDLs take cholesterol into blood vessels.

  • High-density lipoproteins (HDLs): HDLs carry it out of the body.

The liver, a veritable fat and cholesterol factory, collects fatty acid fragments from your blood and uses them to make cholesterol and new fatty acids. The amount of cholesterol you get from food affects your liver’s daily output: Eat more cholesterol, and your liver may make less. If you eat less cholesterol, your liver may make more.

Your liver then packages cholesterol and fatty acids with protein as very low-density lipoproteins (VLDLs), which have more protein and are denser than their precursors, the chylomicrons. As VLDLs travel through your bloodstream, they lose triglycerides, pick up cholesterol, and turn into low-density lipoproteins (LDLs). LDLs supply cholesterol to your body cells, which use it to make new cell membranes and manufacture sterol compounds such as hormones.

VLDLs and LDLs are squishy enough to pass through blood vessel walls and slide into your arteries, which means that VLDLs are more hazardous to your health than plain old LDLs and can cause plaque deposits that may eventually block an artery, prevent blood from flowing through, and trigger a heart attack or stroke. Whew! Got all that?

VLDLs and LDLs are sometimes called “bad cholesterol,” but they’re really the rafts on which cholesterol sails into your arteries. Traveling through the body, LDLs continue to lose cholesterol. In the end, they lose so much fat that they become mostly protein — turning them into high-density lipoproteins, the particles sometimes called “good cholesterol.”

Once again, this label is inaccurate. HDLs aren’t cholesterol: They’re simply protein and fat particles too dense and compact to pass through blood vessel walls, so they carry cholesterol out of the body rather than into arteries.

That’s why a high level of HDLs may reduce your risk of heart attack regardless of your total cholesterol levels. Conversely, a high level of LDLs may raise your risk of heart attack, even if your overall cholesterol level is low.

The National Heart, Lung, and Blood Institute, American College of Cardiology, and the American Heart Association have all put their stamps of approval on the National Cholesterol Education Program’s (NCEP) recommendations for new, lower levels of LDLs based on the presence of the risk factors such as diabetes, high blood pressure, obesity.

For healthy people with two or more risk factors, the goal is to push LDLs below 130 mg/dl. For high-risk patients with heart disease or blood vessel problems and more than two risk factors, it’s LDLs below 100 mg/dl. For very high-risk patients who are hospitalized with heart disease or have heart disease plus several risk factors, LDLs should be under 70 mg/dl. If necessary, the NCEP suggests using cholesterol-busting “statin” drugs such as atorvastatin (Lipitor).

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