What is high blood cholesterol?

Because of its reputation as a risk factor for heart disease, people tend to think of cholesterol only in negative terms. But cholesterol is an important component of cell membranes and vital to the structure and function of all of your body's cells. Cholesterol also is a building block in the formation of certain types of hormones.

Still, about half of American adults have blood cholesterol levels that are higher than desirable (hypercholesterolemia). If you're one of these people with this largely preventable condition, you may be on the way to heart disease.

When the levels of cholesterol and triglycerides, another blood fat, in your bloodstream become too high, your likelihood of developing cholesterol-containing fatty deposits (plaques) in your blood vessels increases. Over time, plaques lead to narrowing of arteries, impeding blood flow and creating a condition called atherosclerosis. Narrowing of the arteries around your heart (coronary artery disease) can prevent your heart from getting as much oxygen-rich blood as it needs. This means an increased risk of a heart attack. Likewise, decreased blood flow to your brain can cause a stroke, and less blood flowing to your lower limbs may result in exercise-related pain or even gangrene.

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Signs and symptoms

The only way to find out if you have high blood cholesterol is by having a blood test.

Causes

To circulate in your blood, which is mainly water, cholesterol and triglycerides — a form of fat — must be carried by proteins called apoproteins. A lipoprotein is a combination of a lipid and an apoprotein.

The main types of lipoproteins are:

• Low-density lipoprotein (LDL). This contains about 25 percent protein and 45 percent cholesterol. The cholesterol carried in LDL particles is known as LDL cholesterol. LDL cholesterol is sometimes called "bad" cholesterol because it transports cholesterol to sites throughout your body, where it's either deposited or used to repair cell membranes. But like hard water causing lime to build up inside plumbing, LDL cholesterol promotes accumulation of cholesterol in the walls of your arteries.
  
  
• High-density lipoprotein (HDL). This contains almost 50 percent protein and 20 percent cholesterol. The cholesterol carried in HDL particles is known as HDL cholesterol. HDL cholesterol helps clear excess cholesterol from your body and is therefore sometimes called "good" cholesterol.
  
  
• Very-low-density lipoprotein (VLDL). This type of lipoprotein contains mostly triglycerides and small amounts of protein and cholesterol.

Having a low level of LDL cholesterol and a high level of HDL cholesterol is desirable for lowering your risk of developing plaques and coronary artery disease.

You may have high LDL cholesterol as a result of genetic makeup or lifestyle choices, or both. Your genes can give you cells that don't remove LDL cholesterol from your blood efficiently or a liver that produces too much cholesterol as VLDL particles. Your genetic makeup can also result in too few HDL particles.

Risk factors

These lifestyle choices can cause or contribute to high levels of total cholesterol:

• Inactivity. Lack of exercise may lower your level of high-density lipoprotein (HDL) cholesterol, the "good" cholesterol.
  
  
• Obesity. Excess weight increases your triglycerides. It also lowers your HDL cholesterol and increases your very-low-density lipoprotein cholesterol. Being overweight can create a more serious risk factor for health problems depending on how you carry the extra weight. If you carry most of your fat around your waist or upper body, you may be referred to as apple-shaped. If you carry most of your fat around your hips and thighs or lower body, you may be referred to as pear-shaped. Generally, when it comes to your health, it's better to have the shape of a pear than the shape of an apple. If you have an apple shape — a potbelly or spare tire — you carry more fat in and around your abdominal organs. Fat in your abdomen increases your risk of many of the serious conditions associated with obesity. A woman's waist should measure less than 35 inches. A man's waist should be less than 40 inches.
  
  
• Diet. Cholesterol naturally occurs in foods derived from animals, such as meat, eggs and cheese. Eating a high-fat, high-cholesterol diet contributes to an increased blood cholesterol level. Saturated and trans fats raise blood cholesterol levels. Polyunsaturated fats lower blood cholesterol but also seem susceptible to oxidation. Over time, oxidation speeds buildup of plaques inside your arteries. Monounsaturated fats may help lower blood cholesterol and are resistant to oxidation.

These factors increase your likelihood that high total cholesterol levels will lead to atherosclerosis:

• Smoking. Cigarette smoking damages the walls of your blood vessels, making them likely to accumulate fatty deposits. Smoking may also lower your level of HDL cholesterol by as much as 15 percent.
  
  
• High blood pressure. By damaging the walls of your arteries, high blood pressure can accelerate the accumulation of fatty deposits on the walls of your arteries.
  
  
• Type 2 diabetes. This type of diabetes (formerly called adult-onset or noninsulin dependent diabetes) generally develops after age 40. This condition results in a buildup of sugar levels in your blood. Chronic high blood sugar may lead to narrowing of your arteries.
  
  
• Family history of atherosclerosis. If a close family member (parent or sibling) has developed atherosclerosis before age 45, high cholesterol levels place you at a greater-than-average risk of developing atherosclerosis.

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Screening and diagnosis

A good way to detect high blood cholesterol early, so that you can take steps to improve your health, is to have a regular blood test to measure your cholesterol level. Some doctors recommend having your levels of high-density lipoprotein (HDL) cholesterol — the "good" cholesterol — and of triglycerides, another type of blood lipid, measured initially, along with your total cholesterol level. A typical blood cholesterol test measures:

• Total cholesterol
  
  
• HDL cholesterol
  
  
• Triglycerides

Values for low-density lipoprotein (LDL) cholesterol can be calculated from the other three values. You usually don't need a precise measurement of your LDL cholesterol level, but when it is needed, another blood test is used to specifically determine your LDL level.

Measuring only total cholesterol can be misleading because some people have low levels of HDL cholesterol and high levels of triglycerides, but normal or even high levels of LDL cholesterol. In these cases, a total cholesterol measurement might appear normal. You and your doctor would be unaware of the risk of heart disease posed by the abnormal levels that weren't measured. Even with a desirable total cholesterol level, if you have a low HDL level, you may be at increased risk of heart disease.

If you're healthy and you have your blood tested for lipoprotein levels, your results will fall into the desirable, borderline or undesirable categories for adults 20 and older.

Desirable values

• Total cholesterol: Below 200 milligrams per deciliter (mg/dL)
  
  
• Total triglycerides: Below 150 mg/dL
  
  
• HDL cholesterol: Above 45 mg/dL
  
  
• LDL cholesterol: Below 130 mg/dL

Borderline values

• Total cholesterol: 200 to239 mg/dL
  
  
• Total triglycerides: 150 to199 mg/dL
  
  
• HDL cholesterol: 40 to 45 mg/dL
  
  
• LDL cholesterol: 130 to159 mg/dL

Undesirable values

• Total cholesterol: 240 mg/dL and above
  
  
• Total triglycerides: 200 mg/dL and above
  
  
• HDL cholesterol: Below 40 mg/dL
  
  
• LDL cholesterol: 160 mg/dL and above

Desirable ranges for cholesterol levels vary depending on risk factors, such as your age, sex, family history and health condition. There's no magic number that separates risky levels from safe levels. Instead, experts have identified levels of lipids in the blood above which the risk of developing coronary complications is high enough to warrant lifestyle changes. Talk to your doctor about what level is appropriate for you.

If you have coronary artery disease, desirable blood cholesterol test values are as follows:

• Total cholesterol: Below 200 mg/dL
  
  
• Total triglycerides: Below 150 mg/dL
  
  
• HDL cholesterol: Above 45 mg/dL
  
  
• LDL cholesterol: Below 100 mg/dL

Have your baseline cholesterol tested when you're in your 20s and then every 3 to 5 years. If your values aren't within desirable ranges, your doctor may advise more frequent measurements.

You can also purchase a home cholesterol test. These tests measure only total cholesterol, are less sophisticated than laboratory tests and may give unreliable results.

Children generally don't need to undergo cholesterol testing, unless there's a family history of early-onset heart problems.

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Complications

High blood cholesterol can cause you to develop heart disease. The American Heart Association reports that heart disease kills almost 1 million Americans each year, more than all cancer deaths combined. Many of these deaths occur because of the accumulation of fatty deposits (plaques) on the walls of your arteries (atherosclerosis), resulting in narrowed or blocked arteries. Cholesterol plays a significant role in this largely preventable condition.


Atherosclerosis is initially a silent, painless condition that results in reduced blood flow. If reduced flow occurs in the arteries around your heart (coronary arteries), it can lead to a type of chest pain called angina pectoris.

As a plaque enlarges, the inner lining of your artery becomes roughened. A tear or rupture in the plaque may cause a blood clot to form. Such a clot can block the flow of blood or break free and plug an artery downstream.

If the flow of blood to a part of your heart is stopped, you'll have a heart attack. If blood flow to a part of your brain stops, a stroke is imminent.

High triglyceride levels also increase your risk of diabetes and pancreatitis.

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Treatment

Lifestyle changes are the first steps you can take to improve your blood levels of cholesterol and triglycerides. These include changes in diet, regular exercise and avoidance of smoking. If you've made these important lifestyle changes and your total cholesterol — especially your level of low-density lipoprotein (LDL) cholesterol — remains high, your doctor may recommend prescription medication.

Before recommending medication, your doctor may weigh many variables — your changeable risk factors, your age, your current health and the drug's side effects. If you need a medication to improve your cholesterol levels, chances are you may need it for many years.

Your LDL cholesterol level is usually the deciding factor. If you have no risk factors for heart disease, an LDL level greater than 190 mg/dL generally requires medication. With two or more risk factors, an LDL level greater than 160 mg/dL may require medication. If plaques have narrowed the arteries around your heart and restricted the flow of oxygen-rich blood to your heart's muscles (coronary artery disease), your doctor may try medication and lifestyle changes to lower your LDL to less than 100 mg/dL.

Medications to improve blood cholesterol levels include:

• Resins. The medications cholestyramine (Questran) and colestipol (Colestid) lower cholesterol indirectly by binding with bile acids in your intestinal tract. Your liver makes bile acids, which you need for digestion, from cholesterol. By tying up bile acids, resins prompt your liver to make more bile acids. Because your liver uses cholesterol to make bile acids, less cholesterol is available to reach your bloodstream.
  
  
• Triglyceride-lowering drugs. These medications include fibrates such as gemfibrozil (Lopid) and fenofibrate (Tricor), and niacin (nicotinic acid). Fibrates reduce triglyceride production and remove triglycerides from circulation. They can also increase your HDL cholesterol level.
  
  
• Statins. Statins work directly in your liver to block a substance your liver needs to make cholesterol. This depletes cholesterol in your liver cells, which causes your liver cells to remove cholesterol from your blood. Statins can reduce your LDL cholesterol by up to 40 percent. Statins may also help your body reabsorb cholesterol from plaques that accumulate on the walls of your arteries. This process slowly unplugs your blood vessels. Statins include fluvastatin (Lescol), lovastatin (Mevacor), simvastatin (Zocor), pravastatin (Pravachol) and atorvastatin (Lipitor).

How cholesterol-lowering drugs work

Prevention

Improving your blood cholesterol levels reduces your risk of heart disease. Lifestyle changes are your first course of action to improve your blood cholesterol levels. These steps include eating a healthy diet, exercising and not smoking.

Eating a healthy diet
These changes in your diet can improve your blood cholesterol levels:

• Control total fat. Limit all types of fat — saturated, polyunsaturated, trans fatty acids (trans fats) and monounsaturated — to no more than 30 percent of your total daily calories. Because all foods with fats contain a combination of these fats, it's important to reduce total fat. Not every food you eat must have less than 30 percent of its calories from fat. Use the guideline as a daily average. By balancing occasional high-fat foods with low-fat choices, your fat intake should average no more than 30 percent of your daily calories. If your daily intake is 2,000 calories, 30 percent equals 65 grams of fat. Limit saturated fat to no more than 10 percent of total calories.
  
  
• Limit dietary cholesterol. Your daily limit for dietary cholesterol is 200 milligrams. To accomplish this goal, limit or avoid concentrated sources such as organ meats, egg yolks and whole-milk products.
  
  
• Eat foods with soluble fiber. As part of a low-fat diet, soluble fiber can help lower your total blood cholesterol level. Foods high in soluble fiber include oat bran, oatmeal, beans, peas, rice bran, barley, citrus fruits, strawberries and apple pulp.
  
  
• Eat more fish. Some fish — particularly fatty types prevalent in cold water, such as salmon, mackerel and herring — contain high amounts of a unique type of polyunsaturated fat called omega-3 fatty acids. Omega 3s may lower your level of triglycerides. However, pregnant women and women who plan to become pregnant in the next several years should limit their weekly intake of cold-water fish because of the potential for mercury contamination.
  
  
• Consider soy products. Soy compounds called isoflavones act like human hormones that regulate cholesterol levels. Eating soy proteins can reduce your levels of total cholesterol, low-density lipoprotein (LDL) cholesterol and triglycerides. Eating soy may also raise your level of high-density lipoprotein (HDL) cholesterol, the "good" cholesterol, which may protect you against heart disease.
  
  
• Drink alcohol in moderation, if at all. Moderate consumption of alcohol may raise your level of HDL cholesterol. The best advice is to drink in moderation if you drink at all. Limit alcohol to one drink daily if you're a woman or to no more than two drinks daily if you're a man. If you're a nondrinker, don't start drinking alcohol. Don't drink alcohol if you have a high level of triglycerides.
  
  
• Reduce sugar intake. This is a way of lowering triglyceride levels. Women's cardiovascular health, compared with that of men, seems to be more significantly influenced by triglyceride levels. Levels higher than 150 mg/dL increase a woman's cardiovascular risk. Men, however, don't attain the same level of increased risk until triglycerides reach 400 mg/dL. It's especially important for women with high triglyceride levels to take action to reduce those levels.

Exercising
Being overweight promotes a high total cholesterol level. Losing weight improves your cholesterol levels. Set up an exercise program to lose weight using these guidelines and your doctor's advice:

• Choose an aerobic activity. Get involved in activities such as brisk walking, jogging, bicycling or cross-country skiing.
  
  
• Build up the time and frequency of exercising. Gradually work up to exercising for 30 minutes to 45 minutes at least three times a week. If you're overweight or have been inactive for many years, take several months to work up gradually to this level. The higher the level of your activity, the greater your rate of weight loss.
  
  
• Stick with your exercise program. Schedule a regular time for exercise. Make exercise fun. If it's not enjoyable you may not feel like exercising regularly, year in and year out. Find a friend or join an exercise group to keep you motivated and committed to exercise. Or take up an activity that keeps you active.

Not smoking
If you smoke, stop. If you don't smoke, don't start. Cigarette smoking damages the walls of your blood vessels, making them prone to accumulating fatty deposits. If you stop smoking, your HDL cholesterol may return to its former level.

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— August 15, 2002 —