What is cholesterol?
Cholesterol is a chemical compound that is naturally produced by the body and is structurally a combination of lipid (fat) and steroid. Cholesterol is a building block for cell membranes and for hormones like estrogen and testosterone. About 80% of the body’s cholesterol is produced by the liver, while the rest comes from our diet. The main sources of dietary cholesterol are meat, poultry, fish, and dairy products. Organ meats, such as liver, are especially high in cholesterol content, while foods of plant origin contain no cholesterol. After a meal, dietary cholesterol is absorbed from the intestine and stored in the liver. The liver is able to regulate cholesterol levels in the blood stream and can secrete cholesterol if it is needed by the body.
What are LDL and HDL cholesterol?
LDL cholesterol is called “bad” cholesterol, because elevated levels of LDL cholesterol are associated with an increased risk of coronary heart disease, stroke, and peripheral artery disease. LDL lipoprotein deposits cholesterol along the inside of artery walls, causing the formation of a hard, thick substance called cholesterol plaque. Over time, cholesterol plaque causes thickening of the artery walls and narrowing of the arteries, a process called atherosclerosis, which decreases blood flow through the narrowed area.
HDL cholesterol is called the “good cholesterol” because HDL cholesterol particles prevent atherosclerosis by extracting cholesterol from the artery walls and disposing of them through the liver. Thus, high levels of LDL cholesterol and low levels of HDL cholesterol (high LDL/HDL ratios) are risk factors for atherosclerosis, while low levels of LDL cholesterol and high levels of HDL cholesterol (low LDL/HDL ratios) are desirable and protect against heart disease and stroke.
Total cholesterol is the sum of LDL (low density) cholesterol, HDL (high density) cholesterol, VLDL (very low density) cholesterol, and IDL (intermediate density) cholesterol.