Cholesterol is a building block of the outer membrane of the cells. It is the principal ingredient in the digestive juice bile, in the fatty sheaths that insulate nerves and in sex hormones, namely, estrogen and androgen. It performs several functions such as transportation of fat, providing defense mechanism, protecting red blood cells and muscular membrane of the body.
Most of the cholesterol found in the body is produced in the liver. However, about 20 to 30 percent generally comes from the foods we eat. Some cholesterol is also secreted into the intestinal tract in bile and becomes mixed with the dietary cholesterol. The percentage of ingested cholesterol absorbed seemed to average 40 to 50 percent of the intake. The body excretes extra cholesterol from the system through bowels and kidneys.
The amount of cholesterol is measured in milligrams per 100 millimeters of blood. The normal level of cholesterol varies between 150-250 mg. per 100 ml. People with atherosclerosis have uniformly high blood cholesterol usually above 250 mg. per 100 ml.
In blood, cholesterol is bound to certain proteins - lipoproteins which have an affinity for blood fats, known as lipids. There are two main types of lipoproteins: a low-density one (LDL) and a high-density one (HDL). The low-density lipoprotein is the one which is considered harmful and is associated with cholesterol deposits in blood vessels. The higher the ratio of LDL to the total cholesterol, the greater the risk of arterial damage and heart disease.
The HDL, on the other hand, plays a salutary role by helping remove cholesterol from circulation and thereby reduce the risk of heart disease.
Cholesterol has been the subject of extensive study by researchers since 1769, when French chemist, Polutier de La Sale purified the soapy-looking yellowish substance. The results of the most comprehensive research study, commissioned by the National Heart and Lung Institute of the U.S.A. were announced about four years ago. The 10-year study, considered the most elaborate and most expensive research project in medical history, indicates that heart disease is directly linked to the level of cholesterol in the blood and that lowering cholesterol significantly reduces the incidence of heart attacks. It has been estimated that for every one percent reduction in cholesterol, there is a decrease in the risk of heart attack by 2%.
Stress has been found to be a major cause of increased level of cholesterol. Adrenaline and cortisone are both released in the body under stress. This, in turn, produces a fat metabolizing reaction.