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Cholesterol does not travel
freely in the bloodstream. Rather, cholesterol is carried through the blood by
particles called lipoproteins. Cholesterol also 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 new
guidelines released in May 2001 by 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 12-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. 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. |
