High cholesterol is the best known of all the many threats to a healthy heart. When excess amounts of this waxy, fat-like substance build up along the walls of the arteries, you face a dramatically higher risk of a complete blockage, leading to a heart attack or stroke.

At normal levels, cholesterol is not a bad thing. On the contrary, it's an essential raw material used by the body to build cell walls and produce hormones such as estrogen and testosterone. The body produces its own supply of cholesterol in the liver, and it's found naturally in all animal products (such as meats, eggs, milk, and cheese). It poses a problem only when the body is unable to use or eliminate excessive supplies.

As one of a variety of fatty substances in the body, cholesterol is classified as a lipid. It is carried through the bloodstream attached to proteins, forming complexes called lipoproteins. There are two major types of lipoproteins: the low-density lipoproteins (LDL) commonly known as "bad" cholesterol, and the high-density lipoproteins (HDL) usually dubbed "good" cholesterol. It's the "bad" LDL cholesterol that tends to form deposits on the artery walls. HDLs, on the other hand, help to clear excess cholesterol from the bloodstream. The ideal situation to aim for, then, is a low level of LDL cholesterol, a high level of HDL cholesterol, and a moderate total of both.

Cholesterol is measured in milligrams per deciliter of blood. According to the National Cholesterol Education Program, a desirable target profile consists of:

• A total blood cholesterol level of less than 200
• An LDL level of:
• less than 100 if you have heart disease
• less than 130 if you're at risk of heart disease
• less than 160 if your risk of heart disease is low
• An HDL level greater than 40

You are generally considered at risk of heart disease if two or more of the following factors apply to you:

• Cigarette smoking
• High blood pressure
• Low HDL cholesterol (below 40)
• A family history of early heart disease (before 55 in a man, or 65 in a woman)
• Your own age (over 45 if you're man, over 55 if you're a woman)