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Lipoproteins and Cholesterol

Roles of lipoproteins and triglycerides

Type

What they do

Low-density lipoproteins (LDL)
  • Deliver cholesterol to your body
  • In excess, lead to a buildup of cholesterol in the walls of your arteries
High-density lipoproteins (HDL)
  • Prevent harmful buildup of cholesterol in your arteries
Triglycerides
  • Affect production of cholesterol-rich lipoproteins that cause high cholesterol
  • Store fat nutrients
  • Increase the ability of blood to clot
Chylomicrons
  • Carry dietary fat from the intestine to the liver
  • Deliver dietary fat in the form of triglyceride to muscle tissue cells
  • Deposit excess triglyceride in fat (adipose) tissue
Very low-density lipoproteins (VLDL)
  • Distribute triglyceride made in the liver to muscle cells
  • Deposit excess triglyceride in the fat tissue
  • In excess, can contribute to buildup of cholesterol in your arteries

"Bad" cholesterol: Low-density lipoprotein (LDL) contains a smaller proportion of protein than other lipoproteins. LDL consists mostly of cholesterol (75%), and the majority of the cholesterol circulating in your blood (60% to 75%) is found in LDL. As a result, LDL accounts for the majority of the cholesterol in your total cholesterol measurement.

A certain level of LDL in your blood is normal and healthy because LDL is responsible for delivering cholesterol to the parts of your body that need it. Excess LDL, however, causes a buildup of cholesterol in the walls of your arteries, contributing to the development of atherosclerosis.

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"Good" cholesterol: High-density lipoprotein (HDL) contains a much larger proportion of protein than LDL does. HDL carries about 20% to 30% of the cholesterol in your blood. Unlike LDL, the job of HDL is to remove excess cholesterol from your cells and the walls of your arteries and then transport the cholesterol back to your liver for disposal. While HDL has other roles, not all of which are fully understood, you can think of HDL as a positive force in the entire lipoprotein cycle. Overall, HDL is "good" because it may actually slow or even reverse the development of atherosclerosis.

Triglycerides: Triglycerides combine with cholesterol and protein to make lipoproteins. Your body uses and stores fat nutrients as triglyceride. In addition to processing triglyceride from dietary fat, your body also produces triglyceride in your liver.

The way your body processes triglyceride-rich lipoproteins, such as chylomicrons and VLDL, directly affects the making of cholesterol-rich lipoproteins that cause high cholesterol, such as LDL. For example, when there are high levels of triglyceride to be processed because of a diet high in saturated fat, the body produces more LDL. This helps to explain why a diet high in saturated fat can significantly increase your LDL level, your total cholesterol, and your risk of atherosclerosis.

Chylomicrons: When you eat foods that contain fat, enzymes in your small intestine break them down into small particles of triglyceride. Your small intestine then absorbs these particles and combines them with small amounts of cholesterol, protein, and phospholipid to form lipoproteins called chylomicrons. The chylomicrons circulate in the bloodstream and deliver triglycerides to your cells for immediate use or for storage.

Very low-density lipoprotein (VLDL): These lipoproteins are "very low-density" because they contain very little protein. VLDL is composed largely of triglyceride but also carries 10% to 15% of the cholesterol in your blood. The main purpose of VLDL is to distribute the triglyceride produced by your liver.

By Healthwise Staff
Primary Medical Reviewer E. Gregory Thompson, MD - Internal Medicine
Specialist Medical Reviewer Carl Orringer, MD - Cardiology, Clinical Lipidology
Last Revised July 2, 2010

WebMD Medical Reference from Healthwise

Last Updated: July 02, 2010
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

Is This Normal? Get the Facts Fast!

Is Your Cholesterol Level Heart Healthy?
What is your LDL (low-density lipoprotein) level?

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or
Answer:
Desirable
0-199
Borderline
200-239
High
240+

Your level is currently

Congratulations! Your total cholesterol level is in the Desirable range, and your level of "bad" LDL cholesterol is optimal.

Congratulations! Your total cholesterol level is in the Desirable range, and your level of "bad" LDL cholesterol is near optimal.

Your total cholesterol level is in the Desirable range, but your level of "bad" LDL cholesterol is borderline high. If your LDL goes higher, your total cholesterol level could become Borderline High. Consider reducing the amount of foods you eat with saturated fats and increasing physical activity. If you get more exercise, your level of "good" HDL cholesterol may increase, which could also help to keep your levels of LDL and total cholesterol in check.

Your total cholesterol level is in the Desirable range, but your level of "bad" LDL cholesterol is High. This may mean that your level of high-density lipoprotein (HDL), or "good" cholesterol, is too low. It is best to have a high level of "good" HDL and a low level of "bad" LDL. The HDL helps keep your LDL level in check. Ask your doctor for your HDL level. If your HDL is low, increasing your physical activity can increase it, which may help reduce your LDL level.

Your total cholesterol level is in the Desirable range, but your level of "bad" LDL cholesterol is Very High. This may mean that your level of high-density lipoprotein (HDL), or "good" cholesterol, is too low. It is best to have a high level of "good" HDL and a low level of "bad" LDL because the HDL helps keep your LDL level in check. Ask your doctor for your HDL level. If your HDL is low, increasing your physical activity can increase it, which may help reduce your LDL level.

Your total cholesterol level is Borderline High, but fortunately your level of "bad" LDL cholesterol is optimal. This could mean you have a high level of high-density lipoprotein, or "good" HDL cholesterol, which protects against heart disease. Or you could have other non-measured increases in LDL-like particles that can increase heart disease. Your LDL level also could be optimal if you are taking a statin medication. Please check with your doctor to get your complete lipid profile and see if you may need additional treatment. In the meantime, find more information on WebMD's Cholesterol Health Center.

Your total cholesterol level is Borderline High, but fortunately your level of "bad" LDL cholesterol is near optimal. This could mean you have a high level of high-density lipoprotein, or "good" HDL cholesterol, which protects against heart disease. Or you could have other non-measured increases in LDL-like particles that can increase heart disease. Your LDL level also could be optimal if you are taking a statin medication. Please check with your doctor to get your complete lipid profile and see if you may need additional treatment. In the meantime, find more information on WebMD's Cholesterol Health Center.

Your total cholesterol level is Borderline High. Your level of "bad" LDL cholesterol is Borderline High, too. Working to bring down your total cholesterol decreases your LDL cholesterol level. You can do this by exercising more and eating less food with saturated fats. Check food labels!

Your total cholesterol level is Borderline High. Your level of "bad" LDL cholesterol is High. Working to bring down your total cholesterol decreases your LDL cholesterol level. You can do this by exercising more and eating less food with saturated fats. Check food labels!

Your total cholesterol level is Borderline High. But your level of "bad" LDL cholesterol is Very High. Working to bring down your total cholesterol decreases your LDL cholesterol level. You can do this by exercising more and eating less food with saturated fats. Check food labels!

Your total cholesterol is High, but your level of "bad" LDL cholesterol is optimal. This could mean you have a high level of high-density lipoprotein, or "good" HDL cholesterol, which protects against heart disease. Or you could have elevated secondary lipids, such as non-HDL particles that increase the risk of heart disease. Your LDL level also could be optimal if you are taking a statin medication. Please check with your doctor to get your complete lipid profile and see if you may need additional treatment. In the meantime, find more information on WebMD's Cholesterol Health Center.

Your total cholesterol is High, but your level of "bad" LDL cholesterol is near optimal. This could mean you have a high level of high-density lipoprotein, or "good" HDL cholesterol, which protects against heart disease. Or you could have elevated secondary lipids, such as non-HDL particles that increase the risk of heart disease. Your LDL level also could be optimal if you are taking a statin medication. Please check with your doctor to get your complete lipid profile and see if you may need additional treatment. In the meantime, find more information on WebMD's Cholesterol Health Center.

Your total cholesterol level is High. Your level of "bad" LDL cholesterol is Borderline High. Working to bring down your total cholesterol decreases your LDL cholesterol level. You can do this by exercising more and eating less food with saturated fats. Check food labels!

Your total cholesterol level is High. Your level of "bad" LDL cholesterol is High, too. Working to bring down your total cholesterol decreases your LDL cholesterol level. You can do this by exercising more and eating less food with saturated fats. Check food labels! If you are struggling to bring down your total cholesterol and LDL cholesterol levels, your doctor may prescribe medication, such as statins. Following medication, dietary, and exercise instructions should result in improvements.

Your total cholesterol level is High, and your level of "bad" LDL cholesterol is Very High. Working to bring down your total cholesterol decreases your LDL cholesterol level. You can do this by exercising more and eating less food with saturated fats. Check food labels! If you are struggling to bring down your total cholesterol and LDL cholesterol levels, your doctor may prescribe statins or other cholesterol-lowering medications.

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