The Role of Cholesterol

Cholesterol is a white, waxy substance that is essential to life. It is found in the cells of all humans and animals. Our liver produces cholesterol, and it is also found in varying amounts in foods we eat. Blood carries cholesterol to the cells in molecules called lipoproteins, which are composed of cholesterol, fats, and proteins. The two types of lipoproteins that carry most of the blood cholesterol are low-density lipoproteins (LDL) and high-density lipoproteins (HDL).

LDLs are rich in cholesterol. As they circulate in the bloodstream, they enter cells through LDL receptors on cell walls and are broken down for use by the cell. Most cells in the body have such receptors, and they take up some LDL. But the liver is designed so that 70 percent of the removal of LDL from the bloodstream by LDL receptors occurs there.

HDLs, on the other hand, are cholesterol-thirsty molecules. When traveling through the bloodstream, they soak up surplus cholesterol and transport it to the liver. The liver breaks down cholesterol and eliminates it from the body. The body is thus marvelously designed to utilize the cholesterol it needs and to discard the rest.

The problem occurs when there is excessive LDL in the blood. This increases the possibility of a buildup of plaque on artery walls. When plaque buildup occurs, the arteries become narrow and the amount of oxygen-carrying blood that can pass through them decreases. This condition is called atherosclerosis. The process continues slowly and silently, taking decades to manifest discernable symptoms. One symptom is angina pectoris, or chest pain, like Joe experienced.

When a coronary artery is completely blocked, often by a blood clot, the part of the heart that receives blood from that artery dies. The result is a sudden, often deadly, myocardial infarction—better known as a heart attack. Even partial blockage of a coronary artery can lead to death of heart tissue, which may not be manifest by pronounced physical discomfort. Blockage of arteries in other parts of the body can cause strokes, gangrene of the legs, and even loss of kidney function.

Not surprisingly, LDL is called bad cholesterol, and HDL good cholesterol. If LDL tests high or HDL low, the risk of heart disease is high.a A simple blood test will often indicate impending danger long before a person experiences noticeable symptoms, such as angina. It is important, then, to keep your blood-cholesterol level in check. Let us now see how your diet can affect this level.