Cholesterol and Your Heart: Where Do We Stand?
Cholesterol. You've heard it's "bad for you," but why? Where does it come from? Does it do anything besides clog your arteries? This article will explain the relationship between high cholesterol and heart disease, describe the different types of cholesterol, and review several ways to lower a high cholesterol level, including exercise, a low-fat diet, and medication.
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 20%—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. If the plaque is severe enough it can impair blood flow past the blockage. In the heart arteries called coronary arteries this can lead to chest pain or angina when someone exerts themselves.
Part of the plaque can also break off or the plaque can become unstable and rupture. When this occurs blood is exposed to the inner material of the plaque which causes a clot, known in medical terms as a thrombus. Thrombus can form rapidly and completely obstruct an entire artery, or it can be released into the circulation. 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. When this blockage, called an occlusion, occurs in a coronary artery (one of several arteries that supplies the heart tissue with blood), the result is often a 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
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 to the assessments below. Remember that the categories of “desirable,” “borderline,” and “high risk” apply to persons at average risk for heart disease and may not be appropriate for you. Your doctor can help assess the degree of risk associated with your particular cholesterol values:
|Lab Test||Desirable||Borderline||High Risk|
|Total Cholesterol||less than 200 mg/dL (5.2 mmol/L)||200-239 mg/dL (5.2-6.1 mmol/L)||more than 240 mg/dL (6.2 mmol/L)|
|LDL Cholesterol||less than 130 mg/dL (3.4 mmol/L)||130-159 mg/dL (3.4-4.0 mmol/L)||more than 160 mg/dL (4.1 mmol/L)|
|HDL Cholesterol||More than 39 mg/dL (1.0 mmol/L)||n/a||less than 40 mg/dL (1.0 mmol/L)|
|Triglycerides||less than 250 mg/dL (2.8 mmol/L)||n/a||more than 250 mg/dL (2.8 mmol/L)|
|Ratio of total Cholesterol:HDL||less than 3.5||3.6-4.9||more than 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 and sausage, butter, cheese, 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 or Trans 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 to form trans fats. Eating a diet containing these products has been associated with an increased risk of cardiovascular disease. Many foods now specify their content of trans fats; reading food labels can help you avoid these substances
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 (or some other monounsaturated oils) may be beneficial. Your doctor can refer you to a nutritionist who can help you make the wisest food selections.
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.
Most doctors like to see how you do with diet and exercise for a few months before prescribing cholesterol-lowering drugs. However, if your LDL or triglyceride levels are very high or you have other significant risk factors you may be instructed to start cholesterol lowering medications along with diet and exercise. The medications currently used fall into several categories; your doctor will know what type is best for you. Among the commonest are:
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 healthcare 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. These are the strongest medications to reduce cholesterol and have been repeatedly shown to lower your risk of heart attack.
Fibric acid derivatives (Lopid) lower primarily triglycerides with less effect on LDL cholesterol. They can increase risk for gallstone formation.
American Heart Association
Dietary Guidelines for Americans
US Department of Agriculture, US Department of Health and Human Services
Heart and Stroke Foundation of Canada
Heart Healthy Kit: Public Health Agency of Canada
Castelli WP. The new pathophysiology of coronary artery disease. Am J of Cardiol. 1998;82:60T-65T.
Choice of lipid-lowering drugs. The Medical Letter on Drugs and Therapeutics. 1998;40:1042.
Grundy SM, Cleeman JI, et al. Coordinating Committee of the National Cholesterol Education Program. Implications of recent clinical trials for the National Cholesterol Education Program Adult Treatment Panel III Guidelines. J Am Coll Cardiol. 2004;44(3):720-732.
Mensink RP, Katan MB. Effect of dietary fatty acids on serum lipids and lipoproteins. A meta-analysis of 237 trials. Arteriosclerosis, Thrombosis and Vascular Biology. 1992;12:911-916.
Stefanic ML, et al. Effects of diet and exercise in men and postmenopausal women with low levels of HDL cholesterol and high levels of LDL cholesterol. N Engl J Med. 1998;339:12-20.
Whitney EN, Rolfes SR Understanding Nutrition. 6th ed. Minneapolis/St. Paul: West Publishing Co.; 1993.
Willet WC. Diet and health: What should we eat? Science. 1994;264:532-537.
Last reviewed July 2008 by Craig Clark, DO, FACC, FAHA, FASE
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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