The hard, fatty arterial deposits called plaques are composed mostly of cholesterol, a soft, waxy substance that occurs naturally in your body. Cholesterol is necessary for your body's health, because it helps to produce cell membranes and is also necessary for the production of vitamin D and various steroid hormones. Your liver produces about 75% of your body's cholesterol. The rest comes from some of the foods you eat, like meat, egg yolks, and shrimp. There are two forms of cholesterol: low-density lipoprotein (LDL) cholesterol (the "bad" cholesterol) and high-density lipoprotein (HDL) cholesterol (the "good" cholesterol). LDL cholesterol transports cholesterol to the tissues of your body, where it is stored. HDL cholesterol, on the other hand, can actually help your body get rid of excess cholesterol by transporting it to the liver for excretion.

There's always some cholesterol present in your bloodstream. Problems start to happen when there"s too much cholesterol, specifically, too much LDL cholesterol. Over time, LDL cholesterol is deposited in the walls of the arteries and begins to build up. Together with other substances, like calcium, it forms the hard plaques that narrow and stiffen the arteries in a process called atherosclerosis. Atherosclerosis can occur in any of the arteries of the body. When it happens in the coronary arteries, it reduces the blood supply to the heart and causes coronary heart disease (CHD).

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