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What is Cholesterol?

Cholesterol—judging from the thousands of food labels and TV commercials boasting “zero cholesterol!”—has quite a bad reputation. Much of it is not deserved. Cholesterol is a vital component of all cell membranes. It protects nerve cells and is the backbone for many hormones—among them cortisol, estrogen, progesterone, and testosterone. It is also used to make vitamin D and bile, a substance that helps digest fat.

Unfortunately, too high a concentration of cholesterol in the blood is associated with an increased risk of heart disease. Coronary heart disease (CHD) remains the #1 killer of both men and women in America. A high blood cholesterol is one of many risk factors for developing heart disease.

Where Does Cholesterol Come From?

Most of the cholesterol circulating in your blood is made in the liver from fat metabolism. The rest—about twenty percent—comes from the foods you eat. Dietary cholesterol comes from animal products such as meat, milk, cheese, and butter. It can also be made in the liver from saturated fat which is found in animal products and some vegetable sources.

Types of Cholesterol

Cholesterol and fat are transported through the bloodstream in particles called lipoproteins, which are so named because they contain different proportions of lipid (fat) and protein molecules.

Chylomicrons are the largest lipoproteins, and they have the highest content of fat. Chylomicrons carry triglycerides (fat from the foods you eat) from the intestine to body tissues, where they are used for energy or stored as fat.

VLDLs (Very Low Density Lipoproteins) have a little bit more protein than chylomicrons. They carry triglycerides made by the liver to their destination in body tissues.

LDLs (Low Density Lipoproteins) are stuffed full of cholesterol. They hold about two-thirds of all the cholesterol in the blood. These particles, nicknamed “bad” cholesterol, are partially responsible for forming plaque (debris) along blood vessel walls. The more LDLs you have, the greater your risk of getting coronary artery disease—or a heart attack.

HDLs (High Density Lipoproteins) are known as “good cholesterol.” They’re the protective counterparts to LDLs. HDLs contain a high proportion of protein, and their function is to scour the bloodstream, collecting excess cholesterol and transporting it back to the liver to be recycled or disposed of.

Cholesterol and Heart Disease

Increased levels of cholesterol in the blood can contribute to atherosclerosis, which is the gradual build-up of cholesterol, fat, and fibrous debris along the walls of your arteries. This build-up, called plaque, can accumulate enough to narrow the artery and stiffen the arterial wall, causing the heart to work harder to pump blood through.

Part of the plaque can also break off to form a clot, known in medical terms as a thrombus. Once released, clots can travel through the bloodstream through smaller and smaller vessels until they either dissolve or reach a point where they can’t squeeze through, causing a blockage. If this blockage, called an occlusion, occurs in a coronary artery (one of several arteries that supplies the heart tissue with blood), the result is myocardial infarction, or heart attack. If the occlusion occurs in a cerebral (brain) artery, a cerebrovascular accident (stroke) takes place. The extent of the damage depends on the size of the blood vessel that is blocked.

What’s Your Risk?

A high level of blood cholesterol is associated with an increased risk of heart disease. But unlike other risk factors for heart disease that you can’t change or modify, such as age, sex, or a family history of heart disease, you can lower a high cholesterol level. That’s why it is monitored so closely.

Check the risk factors below to see if they apply to you. The more risk factors you have, the greater your chances of developing heart disease.

Unmodifiable Risk Factors Modifiable Risk Factors

Men over age 45 High blood pressure

Family history of heart disease Cigarette smoking

Women over age 55 Inactive lifestyle

Obesity

Diabetes

High cholesterol

Know Your Numbers

Cholesterol levels can be measured with a simple blood test. The table below shows the ranges that have been defined as “desirable,” “borderline,” and “high risk” for total cholesterol and the different types of cholesterol particles. However, the most important number is actually the ratio between total cholesterol and HDL cholesterol. The higher the ratio (high total cholesterol, low HDL cholesterol), the greater your risk for coronary heart disease. It is important, therefore, to know all the levels of your cholesterol and not merely the total cholesterol.

If you’ve had your cholesterol measured recently, see how it compares:

Lab Test Desirable Borderline High Risk

Total Cholesterol <200 mg/dL 200-239 mg/dL >240 mg/dL

LDL Cholesterol <130 mg/dL 130-159 mg/dL >160 mg/dL

HDL Cholesterol >35 mg/dL n/a <35 mg/dL
Triglycerides <250 mg/dL n/a >250 mg/dL

Ratio of total Cholesterol:HDL <3.5 3.6-4.9 >5

Ways to Lower Cholesterol

Is your cholesterol or ratio of cholesterol to HDL too high? The most effective ways to lower cholesterol and reduce your risk of heart disease include exercise, a low-fat diet, and medication.

Exercise keeps your heart and blood vessels healthy. It can also help change some of the other risk factors that lead to heart disease, such as obesity, an inactive lifestyle, and elevated blood sugar. Exercise raises HDL, the “good” cholesterol.

The National Cholesterol Education Program’s (NCEP) dietary guidelines for lowering cholesterol have focused on lowering total fat, which often ends up increasing carbohydrate in the diet. These guidelines are somewhat controversial. Some nutrition experts have demonstrated that certain people on this diet may actually lower their HDL cholesterol, the “good” cholesterol. This often leaves the ratio of cholesterol to HDL unchanged. Studies also demonstrate that the most favorable blood cholesterol concentrations have occurred when the NCEP diet is combined with an exercise program.

Other dietary guidelines include lowering cholesterol intake, changing the type of fat you eat, and increasing fiber.

General Tips for a Cholesterol-Conscious Diet

Reduce Total Fat

Depending on your cholesterol profile, a reduction in total fat may be beneficial. Less fat in the diet means that there is less “raw material” for the liver to use in making cholesterol. Fat should represent about 30% or less of your daily diet.

Reduce Saturated Fat

The type of fat you eat is just as important as how much you eat. Since the liver makes cholesterol more efficiently from saturated than unsaturated fat, changing the type of fat you eat can help to lower your cholesterol. You should get no more than 7-10% of your daily calories from saturated fat—about one-third of your 30% goal for total fat calories.

Saturated fats are mostly solid at room temperature and can be found in fatty meats like bacon, butter, lard, palm oil, and coconut oil. A careful look at nutrition labels will also help you identify how much saturated fat is in a particular food.

Reduce Partially Hydrogenated Fats

To prolong the shelf life of foods—particularly margarine, snack foods, and baked products—manufacturers use liquid vegetable oils, which have been partially hardened. Eating a diet containing these products has been associated with an increased risk of cardiovascular disease.

Increase Polyunsaturated Fats

The type of fat found in fatty fish like salmon, mackerel, and tuna is particularly healthful. Eating fish has consistently been associated with a decrease in sudden death from heart attack. Unsaturated fats are also found in liquid vegetable oils and raw or dry roasted nuts and seeds.

Increase Monounsaturated Fats

For people whose triglyceride level increases or HDL decreases on the NCEP diet, replacement of some of the carbohydrate calories with olive oil may be beneficial.

Increase Your Fiber Intake

Soluble fiber, which dissolves in water, can trap bile in the intestine and excrete it along with other waste. Since bile, a substance that helps digest fat, is made primarily of cholesterol, excreting it will help lower total cholesterol levels. Soluble fiber is found in fruits, oats, and dried beans (legumes); it’s also present in ingredients like pectin and guar gum.

When increasing your fiber, you might also want to try soy. This legume, found in products made from soybeans like soy milk, tempeh, tofu, and TVP (Textured Vegetable Protein) has received a lot of attention lately. Intriguing research has shown that the vegetable protein in soy may be able to lower blood cholesterol.

A registered dietitian (RD) can help you plan a cholesterol-modifying diet that’s appropriate for your weight, height, activity level, and blood cholesterol profile.

Cholesterol-Lowering Medications

Most doctors like to see how you do with diet and exercise for a few months before prescribing cholesterol-lowering drugs. The medications fall into several categories; your doctor will know what type is best for you.

Niacin (Nicolar, Nicobid) — is a derivative of the B-vitamin niacin. It’s the cheapest of the cholesterol-lowering drugs and it increases HDL more than any other drug. However, skin flushing is a common side effect and niacin has been associated with negative changes in markers for liver health. Although niacin is available over the counter, it should only be taken under supervision of your health care provider.

HMG-CoA reductase inhibitors (statins) (Mevacor, Pravachol, Zocor) — limit the liver’s ability to make cholesterol by blocking a critical step in the process.

Fibric acid derivatives (Lopid) — lower cholesterol and triglycerides. They are more expensive and carry a doubled risk for gallstone formation.

by Christine Perry

RESOURCES:

American Heart Association

News

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