Cholesterol is a substance which naturally occurs in animal tissue and fat. It can be synthesized in the liver and is a normal component of bile, which is used in digestion. Cholesteral is also essential for the body to produce various hormones. Only about 20 percent of the cholesterol in our bodies comes from diet; the other 80 percent is synthesized by the liver.

However, excess cholesterol in the diet can lead to an increased risk of developing heart disease and other conditions. For example, atherosclerosis is a condition in which cholesterol deposits build up inside arteries, reducing or blocking blood flow. Additionally, if an arterial deposit breaks loose, it can travel through the blood stream until it lodges in a narrow blood vessel, blocking bloodflow. If the blockage prevents blood flow to the heart, it can cause a heart attack. If the blockage prevents blood flow to the brain, it can cause a stroke.

Cholesterol is often subdivided into two categories: high-density lipoprotein (HDL) cholesterol and low-density lipoprotein (LDL) cholesterol. Elevated levels of LDL or "bad" cholesterol is associated with heart disease but HDL or "good" cholesterol helps retrieve accumulating LDL and return it to the liver for disposal. Thus, having a low "total" cholesterol level may be less desirable than having a high level of protective HDL and a low level of LDL cholesterol.

Cholesterol levels can be reduced by restricting the amount of fat in the diet and by exercising regularly. Smoking and diabetes each lower the level of HDL or "good" cholesterol in the body. High blood pressure also accentuates the effects of cholesterol buildup. After menopause, women's HDL levels may drop unless they take hormone replacement therapy.

Further Reading:

Article : "The Statin Solution"