What is Cholesterol?

Cholesterol is a soft, waxy substance found among the lipids (fats) in the bloodstream and in all your body's cells. It's an important part of a healthy body because it's used to form cell membranes, some hormones and is needed for other functions. But a high level of cholesterol in the blood --hypercholesterolemia -- is a major risk factor for coronary heart disease, which leads to heart attack. There are several kinds of cholesterol, but the ones to focus on are low-density lipoprotein (LDL) and high-density lipoprotein (HDL).

What is LDL cholesterol?

Low-density lipoprotein is the major cholesterol carrier in the blood. If too much LDL cholesterol circulates in the blood, it can slowly build up in the walls of the arteries feeding the heart and brain. Together with other substances it can form plaque, a thick, hard deposit that can clog those arteries. This condition is known as atherosclerosis. A clot (thrombus) that forms near this plaque can block the blood flow to part of the heart muscle and cause a heart attack. If a clot blocks the blood flow to part of the brain, a stroke results. A high level of LDL cholesterol reflects an increased risk of heart disease. That's why LDL cholesterol is called "bad" cholesterol.

Goals for LDL levels vary by whether a person has diabetes or cardiovascular disease (heart attack, stroke, or other form of artery blockage); and by the number of risk factors they have. Risk factors include male gender, age over 60, obesity, sedentary lifestyle, high blood pressure, tobacco use, postmenopausal status for women, or a family history of cardiovascular disease.

Goals for LDL cholesterol are: Persons without cardiovascular disease, diabetes, and less than 2 risk factors: LDL under 160 mg/dL.

Persons without cardiovascular disease, diabetes, but with 2 or more risk factors: LDL under 130 mg/dL.

Persons with diabetes or any form of cardiovascular disease: LDL under 100 mg/dL.

What is HDL cholesterol?

About one-third to one-fourth of blood cholesterol is carried by HDL. Medical experts think HDL tends to carry cholesterol away from the arteries and back to the liver, where it's passed from the body. Some experts believe HDL removes excess cholesterol from plaques and thus slows their growth. HDL cholesterol is known as "good" cholesterol because a high HDL level seems to protect against heart attack. The opposite is also true: a low HDL level (less than 40 mg/dL) indicates a greater risk. A low HDL cholesterol level also may raise stroke risk.

What about cholesterol and diet?

People get cholesterol in two ways. The body -- mainly the liver -- produces varying amounts, usually about 1,000 milligrams a day. Foods also can contain cholesterol. Foods from animals (especially egg yolks, meat, poultry, fish, seafood and whole-milk dairy products) contain it. Foods from plants (fruits, vegetables, grains, nuts and seeds) don't contain cholesterol.

Typically the body makes all the cholesterol it needs, so people don't need to consume it. Saturated fatty acids are the main culprit in raising blood cholesterol, which increases your risk of heart disease. Trans-fats also raise blood cholesterol. But dietary cholesterol also plays a part. The average American man consumes about 337 milligrams of cholesterol a day; the average woman, 217 milligrams.

Some of the excess dietary cholesterol is removed from the body through the liver. Still, the American Heart Association recommends that you limit your average daily cholesterol intake to less than 300 milligrams. If you have heart disease, limit your daily intake to less than 200 milligrams. Still, everyone should remember that by keeping their dietary intake of saturated fats low, they can significantly lower their dietary cholesterol intake. Foods high in saturated fat generally contain substantial amounts of dietary cholesterol.

People with severe high blood cholesterol levels may need an even greater reduction. Since cholesterol is in all foods from animal sources, care must be taken to eat no more than six ounces of lean meat, fish and poultry per day and to use fat-free and low-fat dairy products. High-quality proteins from vegetable sources such as beans are good substitutes for animal sources of protein.

Resources:
National Heart, Lung, & Blood Institute