More than 106 million Americans have high cholesterol, according to the American Heart Association. And with nearly 40 million taking prescription medication to lower bad cholesterol, knowing how to implement a healthier lifestyle is crucial.

A healthy diet and increased exercise are two of the first steps someone diagnosed with high cholesterol should take, but just as important is finding out his or her risk for heart disease. Age (45 for men, 55 for women), smoking history, blood pressure and high-density lipoprotein and low-density lipoprotein levels in the blood stream are the factors used to determine possible health threats.

"A person must find out what their risk is of having a heart attack in the next 10 years," said Dr. James Cleeman, coordinator of the National Cholesterol Education Program at the National Heart, Lung and Blood Institute in Bethesda, Md. "People with a history of diabetes or heart disease are automatically in the risk pool."

Cleeman said people not at high risk are usually given a diet and exercise regimen to try to lower their cholesterol. High-risk individuals and those for whom diet and exercise fail are prescribed medication.

What Is Cholesterol?

Cholesterol is a waxy, fat-like substance found throughout the body that is carried in blood particles called lipoproteins. Low-density lipoproteins, or LDLs, are considered the "bad cholesterol" that at high levels can cause cholesterol to clog the arteries, which could lead to heart disease.

High-density lipoproteins, or HDLs, carry cholesterol back to the liver to remove it from the body. Most cases of high cholesterol stem from diet. An excess of either total cholesterol or LDL cholesterol in the blood creates a risk for heart disease and atherosclerosis, the narrowing of arteries from plaque. A complete blockage of the coronary artery will trigger a heart attack.

The Centers for Disease Control and Prevention recommends an LDL of less than 130. An LDL above 160 is considered high. HDL should be higher than 40. Anything below 35 is considered unhealthy.

Cholesterol-Lowering Food Choices and Exercise

"Most people can lower cholesterol just by making dietary and exercise changes," said Dr. Roger Blumenthal, director of the Johns Hopkins Ciccarone Preventive Cardiology Center and an American Heart Association spokesman. "They must emphasize fruits, vegetables, fiber and whole grains, and incorporate regular physical activity."

People can find good advice on lowering cholesterol in books about diets and healthy eating. The Weight Watchers program is also effective for those willing to make a serious lifestyle change, Blumenthal said.

Foods high in saturated fat and sugar, such as fried and processed foods, red meat and desserts, should be avoided. Healthier choices include white meat chicken and turkey, as well as fish. Someone craving something sweet should consider trying angel food cake, ginger snaps or low-fat or fat-free frozen yogurt and sorbet for snacks and desserts, Blumenthal said.

Plant sterols and stanols are substances that occur naturally in small amounts in many grains, vegetables, fruits, legumes, nuts and seeds. These substances have powerful cholesterol-lowering properties, Blumenthal said. Some manufacturers have started adding them to foods such as butter substitutes, orange juice varieties, cereals and granola bars.

Whole grain oats, found in breads, oatmeal and cereals, have also been shown to lower both total and LDL cholesterol.

As for exercise, walking 2 miles a day has been shown to help people reduce total body weight and cholesterol, Blumenthal said. Buying a pedometer, a small device that senses body motion and counts footsteps, is beneficial because it counts your steps and can keep a person motivated, he said.

Classes of Medications

Doctors may also prescribe medication to help lower cholesterol. There are five classes of cholesterol medications: statins, resins, fibrates, niacin and selective cholesterol absorption inhibitors, according to the American Heart Association.

Statins, which include drugs such as Lipitor, Zocor and Caduet, have the best record in clinical trials and work on a mechanism that blocks cholesterol-manufacturing enzymes and pulls cholesterol out of the blood, decreasing LDL levels and making it less likely that plaque will build up in arteries.

Acid-binding drugs, called resins, lower LDL by disposing of cholesterol through the intestines. This produces more bile. The more bile the liver makes, the more cholesterol it uses, leaving less cholesterol to circulate through the bloodstream. Resin drugs include WelChol, Prevalite and Locholest.

The first medication in the selective cholesterol absorption inhibitor class, called Zetia, was approved in 2002 for treating high cholesterol and some inherited lipid abnormalities. This class works by preventing the absorption of cholesterol from the intestine.

Fibrates, which include Lopid, Tricor and Atromid-S, are best at lowering triglycerides (blood fats) and are commonly used in combination therapy with statins.

Niacin works in the liver by affecting the production of blood fats. It comes in prescription form and dietary supplements, but the supplements must not be used as a substitute for the prescription formula because they are not approved by the U.S. Food and Drug Administration.

People with high cholesterol should consult their physicians to determine the right medication for them.