Cholesterol is a waxy fat that is present in all human beings. About 80 of the cholesterol in the body is manufactured by the liver. The rest is consumed through cholesterol–rich foods like meat, eggs and dairy products. Cholesterol is carried through the bloodstream by proteins called apolipoproteins. When these proteins wrap around cholesterol and other types of fats lipids, the resulting “packages” are called lipoproteins. There are five different types of lipoproteins:
- High-density lipoproteins (HDL), which are associated with “good” cholesterol.
- Low-density lipoproteins (LDL), which are associated with “bad” cholesterol.
- Very-low-density lipoproteins (VLDL), which are associated with “very bad” cholesterol.
- Intermediate–density lipoproteins. Like VLDLs, these also carry both triglycerides and cholesterol.
- Chylomicrons, which carry only a small percentage of cholesterol. Chylomicrons are mostly rich in another type of fat (lipid) called triglycerides.
High levels of LDL cholesterol have been associated with hardened arteries (atherosclerosis) and coronary artery disease. In contrast, high levels of HDL cholesterol have been shown to reduce some of the harmful effects of LDL cholesterol. The National Cholesterol Education Program classifies cholesterol levels as follows (all measurements are in milligrams per deciliter):
- Total cholesterol levels less than 200 are desirable.
- Total cholesterol levels between 200 and 239 are borderline–high.
- Total cholesterol levels that are 240 or higher are high.
- HDL levels should be 40 or above (the American College of Cardiology recommends levels of 45 or above for women. see Cholesterol and Women).
- LDL levels should optimally be less than 100 (levels greater than 129 are considered borderline–high, and levels greater than 159 are considered high).
Regular cholesterol screenings are important. The NCEP recommends that both males and females 20 years of age and older have a cholesterol test every five years. Regular cholesterol screenings are particularly important for people who have risk factors such as diabetes, obesity or a family history of cardiovascular disease. Such higher risk individuals, and people over age 65, may be screened more frequently.
In the event of high cholesterol or triglyceride levels, physicians may recommend lifestyle modifications along with cholesterol–lowering medications