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 LD cholesterol reflects an increased risk of heart disease.
LDL Cholesterol Levels
Less than 100 mg/dL Optimal
100 to 126 mg/dL Near Optimal/Above Optimal
130 to 159 mg/dL Borderline High
160 to 189 mg/dL High
190 mg/dL and above Very High
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 in men; less than 50 mg/dL in women) indicates a greater risk. A low HDL cholesterol level also may raise stroke risk.
What is Lp(a) cholesterol?
Lp(a) is a genetic variation of plasma LDL. A high level of La(a) is an important risk factor for developing atherosclerosis prematurely. How an increased Lp(a) contributes to heart disease isn’t clear. The lesions in artery walls contain substances that may interact with Lp(a), leading to buildup of fatty deposits.
Triglycerides: Triglycerides combine with cholesterol and protein to make lipoproteins. Your body uses and stores fat nutrients as triglycerides. In addition to processing triglycerides from dietary fat, your body also produces triglycerides in the liver.
Triglyceride Level Classification
Less than 150 mg/dL Normal
150-199 mg/dL Borderline-high
200-499 mg/dL High
500 mg/dL or higher Very high
The way your body processes triglyceride-rich lipoproteins, such as chylomicrons and VLDL, directly affects the making of cholesterol-rich lipoproteins that cause high cholesterol, such as LDL. For example, when there are high levels of triglyceride to be processed because of a diet high in saturated fat, the body produces more LDL. This helps explain why a diet high in saturated fat can significantly increase your LDL level, your total cholesterol, and your risk of atherosclerosis.
Chylomicrons: When you eat foods that contain fat, enzymes in your small intestine break them down into small particles of triglyceride. Your small intestine then absorbs these particles and combines them with small amounts of cholesterol, protein, and phospholipid to form lipoproteins called chylomicrons. The chylomicrons circulate in the bloodstream and deliver triglycerides to your cells for immediate use or for storage.
Very low-density lipoprotein (VLDL): These lipoproteins are “very low-density” because they contain very little protein. VLDL is composed largely of triglyceride but also carries 10% to 15% of the cholesterol in your blood. The main purpose of VLDL is to distribute the triglyceride produced by your liver.
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 to 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.
How does physical activity affect cholesterol?
Regular physical activity increases HDL cholesterol in some people. A higher HDL cholesterol is linked with a lower risk of heart disease. Physical activity can also help control weight, diabetes and high blood pressure. Aerobic physical activity raises your heart and breathing rates.
How does tobacco smoke affect cholesterol?
Tobacco smoke is one of the six major risk factors of heart disease that you can change or treat. Smoking lowers HDL cholesterol levels and increases the tendency for blood to clot.
Women and cholesterol
As a rule, women have higher HDL cholesterol levels than men do. The female sex hormone estrogen tends to raise HDL cholesterol, which may help explain why premenopausal women are usually protected from developing heart disease. Estrogen production is highest during the childbearing years. Women also tend to have higher triglyceride levels. Triglyceride levels range from about 50 to 250 mg/dL, depending on age and sex. As people get older, more overweight or both, their triglyceride and cholesterol levels tend to rise.
Children and cholesterol
Compelling evidence shows that the atherosclerotic process (buildup of fatty plaque in arteries) begins in childhood and progresses slowly into adulthood. Then it often leads to coronary heart disease, the single leading cause of death in the United States. Despite substantial success in reducing deaths from coronary heart disease in the past two decades, this disease is still responsible for nearly half of million deaths annually. About 42 percent of the people discharged from hospitals for coronary heart disease risk factors that need attention.
Evidence shows that:
- Atherosclerosis or its precursors begin in young people.
- Elevated cholesterol levels early in life may play a role in the development of adult atherosclerosis.
- Eating patterns and genetics affect blood cholesterol levels and coronary heart disease risk.
- Lowering levels in children and adolescents may be beneficial.
- Cigarette smoking should be discouraged.
- Regular aerobic exercise should be encouraged.
- High blood pressure should be identified and treated.
- Obesity should be avoided or reduced.
- Diabetes mellitus should be diagnosed and treated.
Cholesterol levels in children and adolescents 2-19 years old
Total cholesterol (mg/dL)
Acceptable – less than 170
Borderline – 170-199
High – 200 or greater
LDL cholesterol (mg/dL)
Acceptable – less than 110
Borderline – 110-129
High – 130 or greater
Source: National Institutes of Health (National Cholesterol Education Program) and the American Heart Association.
Cholesterol
