Arteriosclerosis causes heart attacks, strokes, amputations and even loss of brain function in addition to sudden death. Arteriosclerotic plaque, the material that eventually clogs our blood vessels begins to form in youth. American soldiers killed at the age of 19 or 20, in action, have been noted to have streaks of such plaque. The plaque is made up in part of cholesterol. Excess cholesterol in the blood leads to more plaque being deposited at a younger age. For this reason we prefer to delay this from occurring. But why do we need cholesterol at all? Actually, we wouldn't survive without any cholesterol, but we often would live longer if the level were lower.
Each year, more than 1 million Americans will suffer a heart attack and about 500,000 will die from heart disease. High blood cholesterol just like high blood pressure does not cause any symptoms. Many people (more than 50 percent by recent estimates) are either inadequately treated or unaware that their cholesterol level is too high. Considering that more than million estimated American adults have high cholesterol, the failure to appreciate high cholesterol's importance places many people at unnecessary risk for developing future heart disease.
What is cholesterol?
Cholesterol is a waxy, fat-like substance that is naturally found in all parts of our bodies. It is present in the walls and membranes of every cell, including cells in the brain, nerves, muscle, skin, liver, intestines, and heart. Without cholesterol, our bodies could not function properly. It acts as the backbone of hormones like estrogen and testosterone, vitamin D, and bile acids that help us to digest fat.
Cholesterol in the body comes from two major sources. The first is from the liver, which is the body's major cholesterol-producing organ. We also consume foods that contain cholesterol - red meat, poultry and eggs have particularly high levels. Because the liver is usually able to make enough cholesterol to satisfy all of our bodily needs, however, too much dietary cholesterol can lead to high bodily levels of cholesterol. (Some liver or endocrine disorders also lead to excess cholesterol levels.)
These high levels are undesirable because it is difficult for our bodies to appropriately dispose of excess cholesterol. Excess cholesterol has a tendency to deposit into the walls of our arteries, particularly the arteries that lead to our hearts (or coronary arteries). It is these deposits that lead to development of "hardening of the arteries," or atherosclerosis.
Once there is a large amount of plaque on the interior surface of the vessels, it tends to cause obstruction or narrowing of the vessel. Plaque can also rupture, releasing the cholesterol that has been stored in the vessel. At the site of such rupture clots may form that can cause a heart attack or a stroke. Due to the narrowing of vessels that lead to the heart a lack of oxygen may cause chest pain. When the arteries leading to the brain are interrupted even temporarily, neurologic symptoms may occur.
The difference between LDL and HDL cholesterol
Cholesterol does not travel freely in the bloodstream. It is carried through the blood by particles called lipoproteins. Cholesterol behaves differently depending on which type of lipoprotein carries it. Low-density lipoproteins (LDL) deposit excess cholesterol on the artery linings (LDL cholesterol is the "bad" cholesterol), and high-density lipoproteins (HDL) remove excess cholesterol from the blood (HDL cholesterol is the "good" cholesterol). Triglycerides are another type of substance closely related to cholesterol. They are mostly carried throughout the bloodstream by particles called chylomicrons or very low-density lipoproteins (VLDLs). While less is known about triglycerides, in general, there is some evidence to suggest that they are a particularly important cause of coronary artery disease among women and people with other risk factors such as diabetes and obesity.
According to the guidelines of the NHLBI's National Cholesterol Education Program (NCEP), everyone age 20 and older should have their cholesterol and triglyceride levels measured at least once every five years. This blood test is done after a nine- to 14-hour fast and provides information about your total cholesterol (TC), LDL and HDL cholesterol, and triglycerides. If your total blood cholesterol is 200 milligrams (mg) per deciliter (dL) or more, or if your HDL level is less than 40 mg/dL, you should talk to your doctor about ways to lower your cholesterol, which may include changing your diet, increasing exercise, or medication.
HDL cholesterol protects against heart disease. This means that higher numbers of HDL cholesterol are better. A level less than 40 mg/dL is considered low and a major risk factor for the development of coronary artery disease. HDL levels of 60 mg/dL or more help to lower your risk for heart disease.
Triglycerides also can raise heart disease risk. Triglycerides are made in the liver and are also found in most oils, such as corn oil or the oil in margarine.
Levels that are borderline high (150-199 mg/dL) or high (200 mg/dL or more) may require treatment for some people.
The NHLBI classification of the optimal level of LDL cholesterol is less than 100 mg/dL. Borderline high is 130-159 mg/dL, and very high is 190 mg/dL and above. High LDL cholesterol always requires attention. Your chance of developing coronary artery disease increases if you also have one or more other heart disease risk factors, such as high blood pressure, diabetes, and/or an early family history of heart disease.
The following table shows the NHLBI's classification of all cholesterol levels.
Classification of LDL and HDL cholesterol, total cholesterol and triglycerides
|LDL (bad) cholesterol
| Below 100
| 100 to 129
| 160 -189
| Above 190
|HDL (good) cholesterol
Cautions about measuring cholesterol levels
To get accurate results, you should not eat or drink anything for 9 to 14 hours before the test.
Your health care provider may tell you to stop taking drugs that can affect the test. Never stop taking any medicine without first talking to your doctor.
Drugs that may increase total cholesterol measurements include:
- Anabolic steroids
- Beta-adrenergic blocking agents
- Birth control pills
- Thiazide diuretics
- Vitamin D
Drugs that may decrease total cholesterol measurements include:
- MAO inhibitors
Things other than genetics that can raise or lower your cholesterol:
- Physical inactivity
- A high fat diet, especially with trans fats
- Metabolic syndrome
- Hypertension (high blood pressure)
- Endocrine abnormalities: thyroid, pituitary
- Kidney diseases such as nephrotic syndrome and kidney failure
- Certain medications
- Chronic liver disease
- Excessive alcohol consumption
Another caution about cholesterol measurements
Cholesterol is an acute phase reactant meaning that any acute illness can raise or lower the number. If you have had an acute illness in the three months prior to the blood draw it would be wise to repeat the measurement in two to three months. Even a flare up of arthritis can affect the cholesterol level, it can make things look better, or worse.
Reducing your cholesterol
Keeping control of cholesterol is important for everyone. Lowering cholesterol levels that are too high lessens the risk for developing heart disease and reduces the chance of a heart attack or dying of heart disease. While this is especially true for people who have already suffered a heart attack or stroke, it is just as true in children and adults that have not had any cardiovascular events.
Lowering of cholesterol can be accomplished in many ways that are healthful. The least expensive and easiest is known as therapeutic lifestyle changes (TLC). This requires a cholesterol-lowering diet (called the TLC diet), physical activity, and weight management. In cases in which the TLC doesn't lower cholesterol sufficiently, it may be necessary to add cholesterol-lowering drugs while continuing TLC. Depending on what the LDL level is, your doctor will decide which approach is best for you. See Part 2 of the Cholesterol Patient Guide to learn more about how you can lower your cholesterol.
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