By Peter W. Crownfield

Do you know the causes of high cholesterol and the steps you can take to reduce your risk of serious disease? Do you know the different types, and how each type can affect your health? What you know is vital to your longevity: According to the American Heart Association (AHA), an estimated 70 million Americans suffer from one or more forms of cardiovascular disease (CVD). These diseases claimed 927,448 lives in the U.S. in 2002 - more than the total lives claimed by cancer, accidents and HIV combined. And in case you view CVD as a condition exclusive to the elderly population, take note that more than 150,000 of those killed by CVD in 2002 were under the age of 65.

The major type of cardiovascular disease, coronary heart disease (CHD), is caused by arteriosclerosis: the thickening or hardening of the coronary arteries. Here's where cholesterol enters the picture. Findings from the massive Framingham Heart Study, which began in 1948 under the direction of the National Heart Institute (now known as the National Heart, Lung and Blood Institute), show that blood cholesterol is a risk factor for coronary heart disease, and that the higher the cholesterol level, the greater the CHD risk.

THE BASICS Cholesterol is a soft, wax-like lipid that occurs naturally in the bloodstream and in cell walls and membranes. It is a normal and important part of a healthy body because of the essential role it plays in cell membrane, hormone, and vitamin D production, as well as the digestive process.

The liver produces approximately 1,000 milligrams (mg) of cholesterol daily from other fats, which is all the cholesterol the body needs. In other words, you don't need to consume cholesterol from dietary sources to stay healthy. (Infants are the exception: During the growth process, their bodies make new cell membranes so rapidly that they require a certain amount of dietary cholesterol.)

Because the body doesn't need dietary cholesterol, particularly not cholesterol with "no place to go," it means that consumption of cholesterol-laden foods can cause plaque formation/buildup and resulting cardiovascular problems.

LDL, HDL AND TRIGLYCERIDES First, a little technical background: Dietary fat is absorbed by the intestine and transported to the liver. The liver then converts fat into cholesterol and releases it into the bloodstream. Because cholesterol isn't water-soluble, cholesterol and triglycerides (a blood lipid) combine with proteins to form lipoproteins, which then transport cholesterol through the watery blood system.