Cholesterol Tests

Experts agree that those age 20 and older should have a cholesterol test once every five years or more often if there is a family history of several risk factors for heart disease. The same goes for children more than two years of age with one or both parents who have high cholesterol. Cholesterol tests examine levels of serum total cholesterol, triglycerides, and high density lipoprotein (HDL) cholesterol.

Cholesterol

Cholesterol is a waxy, fat-like substance that your body uses to manufacture hormones, bile acids, and vitamin D; it also helps transport fat in the blood. Most of the cholesterol your body needs is manufactured in the liver, but you also receive some cholesterol from the foods you eat. Cholesterol is found in animal products, especially egg yolks, shellfish, and organ meats (liver and kidney).

As the heart pumps blood through the arteries, oxygen and nutrients are carried to tissues and organs throughout the body. When cholesterol levels rise above normal limits and remain high, some cholesterol is left behind in the arteries. Over time, the cholesterol becomes a hardened substance called cholesterol plaque which builds up on the artery walls reducing or blocking blood flow. Organs can become damaged because they cannot get the vital oxygen and nutrients they need. For example, when plaque completely blocks an artery around the heart, a heart attack occurs. When blood flow to the brain is blocked, a stroke occurs.

Cholesterol Levels

Cholesterol levels are measured through a blood test. The level of total cholesterol in the body should be less than 200 milligrams per decaliter, borderline cholesterol level is 200–239 mg/dl, and 240 mg/dl or above is considered high. If you have a borderline or high cholesterol level, your doctor may recommend a lipid profile that measures high density lipoprotein (HDL), low density lipoprotein (LDL), and triglyceride levels to get more information and determine treatment.

LDL and HDL

Lipoproteins function as "packages" containing cholesterol, triglyceride and other proteins, and they route these materials throughout the body. Low-density lipoproteins (LDL) are often called the "bad" cholesterol. High levels of LDL's in the bloodstream can result in clogged arteries, leading to high blood pressure, stroke, or heart disease. Desirable LDL level should be less than 130 mg/dl. An LDL level of 130-159 mg/dl is borderline-high risk and 160 mg/dl and over is considered high risk.

High-density lipoproteins (HDL) are known as the "good" cholesterol because HDL's carry excess cholesterol from different body tissues to the liver, where it is metabolized and then routed out of the body through the bowels. High levels of HDL's are associated with a decreased risk of coronary heart disease. An HDL level less than 35 mg/dl is associated with an increased risk for heart disease.

Another factor in lipoprotein analysis is the ratio of total cholesterol to HDL cholesterol. A total cholesterol to HDL cholesterol ratio below 3.5/1 is desirable. A ratio of 4.5/1 represents average risk, and a ratio; above 4.5/1 indicates a greater-than-average risk for developing heart disease.

The good news about LDL and HDL cholesterol is that LDL levels can be reduced through a heart-healthy diet and HDL levels can be raised through regular exercise.

Triglycerides

Most of the fats in food are triglycerides, made up of mostly fatty acids, which assist the absorption of the fat-soluble vitamins A, D, E, K and other important bodily functions. Triglyceride levels are classified as normal (less than 200mg/dl), borderline (200-400 mg/dl), high (400-1,000 mg/dl), and very high (1,000 mg/dl). Factors that increase triglycerides include a diet high in fat (especially saturated fat), concentrated sweets, and alcohol.

Fats and Cholesterol

Many foods that contain fat do not contain cholesterol. However, eating too much fat of any type can raise your blood cholesterol level. Controlling the type and amount of fat in your diet is just as important as limiting the cholesterol in your diet.

Dietary fats can be saturated or unsaturated. Saturated fats are found primarily in meats, whole milk, and dairy products made from whole milk. Unsaturated fats (polyunsaturated and mono unsaturated) are found primarily in plant foods. The easiest ways to tell the difference is that saturated fats are solid at room temperature and unsaturated fats are liquid at room temperature.

While all fats contain the same amount of calories, unsaturated fats are generally "healthier" than saturated fats. Unsaturated fats can help lower both LDL and HDL cholesterol. Good sources of unsaturated fats are safflower, sunflower, corn, soybean, canola, olive, and peanut oils. However, not all oils are good. Tropical oils--coconut, palm, and palm kernel--and cocoa butter (used in making chocolate) are high in saturated fat.

A diet low in saturated fat (less than 10 percent of daily calories) and cholesterol (less than 300 mg per day) helps keep blood cholesterol levels low. Moderate fat intake (no more than 30 percent of total calories) also helps with weight control.

Even if your blood cholesterol levels are not elevated, following a heart-healthy diet low in cholesterol and fat is still in your best interest. Diets high in total fat have been linked with an increased risk of cancer of the colon, prostate, and rectum, while diets high in saturated fat are associated with coronary heart disease.

It is estimated that a decrease of one percent in total blood cholesterol results in a two percent reduction in the risk of heart disease.

RESOURCES

National Cholesterol Education Project, PO Box 30105, Bethesda, MD 20824-0105; 301-592-8573; www.nhlbi.nih.gov/about/ncep