The first point to understanding the risks posed by high cholesterol is understanding what cholesterol is. Cholesterol is not an evil or dangerous molecule on its own, it is a necessary component of cell membranes.
Cholesterol molecules are both produced by the liver and ingested as part of a healthy dietary fat intake. High cholesterol, levels higher than the body uses or needs, is a risk factor for heart disease because of how the molecule is deposited in the artieries as a person ages. Cholesterol begins to be deposited in the arteries in the teen years, and the amount depends on the total blood levels of cholesterol.
Having high cholesterol levels, particularly the LDL type (LDL stands for low density lipoprotein), can cause blood vessel damage and lead to heart disease when other factors are present. High cholesterol is a worry to doctors and patients because the most common form of heart disease, coronary artery disease, is often caused by cholesterol buildup in the arteries. However, there are several other factors involved, including smoking, obesity, family predisposition, and genetic disorders, including homocystinuria, hypertension, and diabetes.
Coronary Artery Disease
There are many conditions that fall under the umbrella of heart disease. According to the U.S. Centers for Disease Control and Prevnetion (CDC), the most common heart disease is coronary artery disease (CAD), also called coronary heart disease. Coronary artery disease occurs when the supply of blood to the outer layer of the heart is inhibited or when the coronary vessels, those that transport the blood to the heart, are damaged. Blockage of the coronary arteries prevents oxygen and nutrients from reaching the outer portion of the heart, and the resulting damage is referred to as a myocardial infarction, or heart attack.
Cholesterol and Atherosclerosis
Over time, the cholesterol deposited in the arteries forms atherosclerotic plaques. These plaques often develop over decades and are a common and normal occurrence in aging blood vessels. The problems occur when there is a hardening and obstruction of the arteries, called atherosclerosis. Plaque development begins in youth and is enhanced by environmental or genetic factors as a person ages; for example, the livers of some patients produce too much cholesterol, hypertension increases the stress put on the plaques and vessels, and obesity and diet increase fatty acids that perpetuate plaque buildup, to name a few.
The atherosclerotic plaques become a danger when they obstruct blood flow, rupture, or wear away the arterial wall. The event can go unnoticed or result in severe complications, such as a heart attack, stroke, or hemorrhage. Plaques can also cause arterial walls to become worn and tear, leading to aneurysms. Clinical manifestations or complications of atherosclerosis are usually not seen until middle age. The clinical phase is more common in men, but begins to appear as frequently in women after menopause.
Preventing Dangerous Cholesterol Accumulation
Smoking is known to contribute to the development of atherosclerotic plaques by increasing the foam cells that fill them and push the plaques outward to cut off blood flow through the artery. Also, smoking may present one of the initiating events for cholesterol adherence within the artery. According to a popular medical school Pathology text (Kumar et al, Basic Pathology, 7th edition), immune responses are partly responsible as well because atherosclerosis is a chronic inflammatory response to damage along the inner arterial wall, propagated by cholesterol buildup. It should also be noted that an improperly treated virus or an unneeded pharmaceutical can be as much to blame for heart disease as cholesterol in a given individual. Smoking cessation can have a positive effect on heart health, and dietary changes can be more effective than pharmaceuticals in most patients.
Reducing dietary fat intake and increasing exercise can go a long way in treating high cholesterol levels and preventing heart disease. Many studies have shown the benefits of these lifestyle changes. Losing weight is often recommended for those with hypertension and/or high cholesterol.
There are also now prescription drugs available that claim to lower blood lipid (cholesterol) levels. In particular are the statins, which are actually most effective in men who have established heart disease. Many studies have found that lifestyle changes pose the lowest risk to those with high cholesterol levels but no established heart disease (no heart attack, stroke, or bypass history). Medication is recommended only after lifestyle changes have been attempted. For more information, see the American Heart Association.