Cholesterol is an essential, abundant form of fat in the human body. The liver manufactures the majority of the cholesterol in the body; the remainder comes from animal fats in the diet. Although cholesterol serves many vital functions, excess amounts or imbalances in the different forms of cholesterol can lead to potentially life-threatening heart disease and hardening of the arteries. Maintaining a healthy cholesterol level proves one of the most important steps patients can take to reduce their risk for cardiovascular disease.
Types
As a form of fat, pure cholesterol proves insoluble in water-based blood. To solve this problem, the body packages cholesterol in water-soluble protein carriers, forming complex molecules called lipoproteins. Different types of cholesterol-based lipoproteins in the body include high-density lipoprotein, or HDL; intermediate-density lipoprotein, or IDL; low-density lipoprotein, or LDL; and very low-density lipoprotein, or VLDL, notes Dr. Philip Barter, director of the Heart Research Institute in Sydney, Australia on the medical website Lipids Online.
The total cholesterol level reflects the sum of the cholesterol in the various lipoprotein forms. A healthy blood cholesterol profile includes normal levels of various lipoproteins and a normal total cholesterol level.
Total Cholesterol
The National Cholesterol Education Program states that a healthy total blood cholesterol level is less than 200 mg/dL. Total cholesterol values of 240 mg/dL or more represent abnormally elevated levels. Total cholesterol levels between 200 and 239 mg/dL indicate a borderline elevation.
An elevated total cholesterol level increases the risk for coronary artery disease, characterized by areas of fat buildup, or plaques, within the blood vessels that supply oxygen to the heart muscle.
LDL Cholesterol
LDL, often referred to as the "bad cholesterol," delivers cholesterol to the body tissues --- an important and necessary function. Abnormally elevated levels of LDL, however, may contribute to the formation of plaques in the coronary arteries and in arteries elsewhere in the body.
A healthy level of LDL is less than 100 mg/dL, according to the National Cholesterol Education Program. An LDL of 160 mg/dL or more represents an abnormal elevation, which increases a patient's risk for coronary artery disease.
HDL Cholesterol
HDL, or "good cholesterol," carries cholesterol from the body tissues back to the liver, which excretes excess amounts into the bile. By removing excess cholesterol from the body, HDL protects against the development of coronary artery disease.
An HDL value of 60 mg/dL or more represents a healthy level. Patients with an HDL level of less than 40 mg/dL may have an increased risk for coronary artery disease, notes the National Cholesterol Education Program.
Significance
More than 102 million adult Americans have a high or borderline high total blood cholesterol level, reports the American Heart Association. Additionally, 71 million have an abnormally elevated LDL level and 35 million have a abnormally low HDL level.
Lifestyle changes and medications can help restore healthy cholesterol levels in most patients, thereby reducing their risk for coronary artery disease. Coronary artery disease remains the leading cause of death among Americans, reports the National Heart Lung and Blood Institute.
References
- Lipids Online: Role of Lipoproteins in Inflammation
- National Cholesterol Education Program, Third Report of the Expert Panel on Detection, Evaluation and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III): High Blood Cholesterol: What You Need to Know
- American Heart Association: Heart Disease and Stroke Statistics --- 2010 Update
- National Heart Lung and Blood Institute: Coronary Artery Disease
- National Heart Lung and Blood Institute: High Blood Cholesterol
