Cholesterol. You have heard it is "bad for you," but why? Where does it come from? Does it do anything besides clog your arteries?
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%—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
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.
Cholesterol levels can be measured with a simple blood test. The table below shows the ranges that have been defined as "desirable," "borderline," and "high risk" for total cholesterol and the different types of cholesterol particles.
If you have had your cholesterol measured recently, see how it compares to the assessments below. Remember that the categories of “desirable,” “borderline,” and “high risk” apply to people at average risk for heart disease and may not be appropriate for you. Your doctor can help assess the degree of risk associated with your particular cholesterol values:
less than 200 mg/dL (5.2 mmol/L)
200-239 mg/dL (5.2-6.1 mmol/L)
more than 240 mg/dL (6.2 mmol/L)
less than 100 mg/dL (2.6 mmol/L)
130-159 mg/dL (3.4-4.0 mmol/L)
more than 160 mg/dL (4.1 mmol/L)
More than 60 mg/dL (1.6 mmol/L)
less than 40 mg/dL (1 mmol/L) for men and less than 50 mg/dL (1.3 mmol/L) for women
less than 150 mg/dL (1.7 mmol/L)
150-199 mg/dL (1.7-2.2 mmol/L)
more than 200 mg/dL (2.3 mmol/L)
Ways to Lower Cholesterol
The most effective ways to lower cholesterol and reduce your risk of heart disease include exercising, eating a healthy diet, and taking cholesterol-lowering medicine. If you are concerned about your cholesterol levels, talk to your doctor to create a plan that is right for you.
Castelli WP. The new pathophysiology of coronary artery disease.
Am J of Cardiol
Choice of lipid-lowering drugs.
The Medical Letter on Drugs and Therapeutics
Grundy SM, Cleeman JI, et al. Coordinating Committee of the National Cholesterol Education Program.
Implications of recent clinical trials for the National Cholesterol Education Program Adult Treatment Panel III Guidelines.
J Am Coll Cardiol.
Mensink RP, Katan MB. Effect of dietary fatty acids on serum lipids and lipoproteins. A meta-analysis of 237 trials.
Arteriosclerosis, Thrombosis and Vascular Biology
Stefanic ML, et al. Effects of diet and exercise in men and postmenopausal women with low levels of HDL cholesterol and high levels of LDL cholesterol.
N Engl J Med
Whitney EN, Rolfes SR
6th ed. Minneapolis/St. Paul: West Publishing Co.; 1993.
Willet WC. Diet and health: What should we eat?
Please be aware that this information is provided to supplement the care
provided by your physician. It is neither intended nor implied to be a
substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER
IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the
advice of your physician or other qualified health provider prior to
starting any new treatment or with any questions you may have regarding a