Cholesterol is a fatty lipid, steroid and an alcohol found in the body tissues and blood plasma of vertebrates. It is the essential part of the outer membranes of human body cells, and it circulates in the blood.

Cholesterol in the human body comes from two major sources. About three-quarters of the body's total cholesterol is produced within the body, while only one-quarter comes from cholesterol in food.

Higher concentrations of cholesterol are present in body tissues which have more densely packed membranes - i.e. the liver, spinal cord, brain, atheroma, adrenal glands and reproductive organs.

The liver is the most important site of cholesterol biosynthesis. It is secreted from the liver in the form of an acidic secretion known as 'bile'.

Diets rich in animal fats, meat, poultry, fish, oils, egg yolks and dairy products are a rich source of dietary cholesterol. Organ meats, such as liver and kidney, are extremely rich in cholesterol content, but foods of plant origin contain no cholesterol.

High cholesterol levels in the bloodstream can influence the pathogenesis of certain conditions. Recent studies have revealed that the abundance of protein complexes called lipoproteins, are responsible for the cholesterol build-up in the blood vessels.

Cholesterol gets attached to these lipoproteins. The high-density lipoprotein (HDL) carries cholesterol out of the bloodstream for excretion, while the low-density lipoprotein (LDL) carries it back into the system for use by various body cells.

LDL cholesterol is called bad cholesterol, because elevated levels of it are associated with an increased risk of coronary heart disease. LDL deposits cholesterol on the artery walls which leads to the formation of a hard, thick substance called cholesterol plaque. Over time, cholesterol plaque causes thickening of the artery walls and narrowing of the arteries, a process called atherosclerosis.

The levels of both HDL cholesterol and LDL cholesterol may also determine risk for heart disease; however current medical opinion is that the ratio of HDL cholesterol to LDL cholesterol is much more important than the level of cholesterol.

Methods to control your cholesterol levels:

Lower your consumption of foods containing saturated fats - fried fast foods, butter, cream, cheese, and fat on meat - to help reduce cholesterol. Add more plant foods to your diet - vegetable oils, nuts, legumes, breads, cereal grains, fruits and vegetables. A low cholesterol diet, combined with regular exercise is the best way to lower cholesterol levels.

Medications can also help lower cholesterol levels. HMG-CoA reductase inhibitors, 'Statins', such as lovastatin (Mevacor) and atorvastatin (Lipitor) are the most effective and widely used medications to lower LDL cholesterol. Other medications include nicotinic acid (niacin), fibrates such as gemfibrozil (Lopid), resins such as cholestyramine (Questran), and ezetimibe, Zetia. These medications should be taken after consulting the experts.