Cholesterol circulates in the blood stream. It is an essential molecule for the human body. Cholesterol is a molecule from which hormones and steroids are made. It is also used to maintain nerve cells. Between 75 and 80% of the cholesterol that circulates in a person's bloodstream is made in that person's liver. The remainder is acquired from outside sources. Cholesterol is found in animal sources of food. It is not found in plants.

Normal blood cholesterol level is a number derived by laboratory analysis. A normal or desirable cholesterol level is defined as less than 200 mg of cholesterol per deciliter of blood (mg/dL). Blood cholesterol is considered to be borderline when it is in the range of 200 to 239 mg/dL. Elevated cholesterol level is 240 mg/dL or above. Elevated blood cholesterol is considered to be hypercholesterolemia.

Cholesterol has been divided into two major categories: low-density lipoprotein (LDL), the so-called “bad” cholesterol, and high-density lipoprotein (HDL), the so-called “good” cholesterol. Diet, exercise, smoking, alcohol, and certain illnesses can affect the levels of both types of cholesterol. Eating a high fat diet will increase one's level of LDL cholesterol. Exercising and reducing one's weight will both increase HDL cholesterol and lower LDL cholesterol.

The most common cause of elevated serum cholesterol is eating foods that are rich in saturated fats or contain high levels of cholesterol. Elevated cholesterol also can be caused by an underlying disease that raises blood cholesterol levels such as diabetes mellitus, kidney disease, liver disease, or hypothyroidism. It also can be caused by an inherited disorder in which cholesterol is not metabolized properly by the body. Obesity, which generally results from eating a diet high in fat, also can lead to elevated cholesterol levels in the blood. This is because obesity itself leads the body to produce excessive amounts of cholesterol.

Hypercholesterolemia increases the risk of heart disease. Elevated levels of circulating cholesterol cause deposits to form inside blood vessels. These deposits, called plaque, are composed of fats deposited from the bloodstream. When the deposits become sufficiently large, they block blood vessels and decrease the flow of blood. These deposits result in a disease process called atherosclerosis, which can cause blood clots to form that will ultimately stop blood flow. If this happens in the arteries supplying the heart, a heart attack will occur. If it happens in the brain, the result is a stroke where a portion of brain tissue dies. Atherosclerosis causes more deaths from heart disease than any other single condition. Heart disease has been the leading cause of death in the United States for the past half century.

There is a syndrome called familial hypercholesterolemia. Affected persons have consistently high levels of LDL. This leads to early clogging of the coronary arteries. In turn this leads to a heart attack. Among affected males, a first heart attack typically occurs in their 40s to 50s. Approximately 85% of men with this disorder have experienced a heart attack by the time they reach 60 years of age. The incidence of heart attacks among women with this disorder also is increased. However, it is delayed 10 years compared to men. The incidence of familial hypercholesterolemia is seven out of 1,000 people.

Hypercholesterolemia is silent. There are no symptoms that are obvious to the naked eye. It is diagnosed by a blood test or after a heart attack or stroke occurs.

Hypercholesterolemia is diagnosed by using a blood test. A blood specimen is obtained after the patient does not eat or drink anything (except water) for 12 hours. The fasting is done to measure the LDL and HDL cholesterol, which can only be determined accurately in a fasting state. Some experts agree that an acceptable limit for LDL cholesterol as 130 mg/dL, though the National Cholesterol Education Program Adult Treatment Panel III recommended a goal of less than 100mg/dL. Total cholesterol of under 200 mg/dL is thought to be an acceptable range.

If an individual's cholesterol is elevated, discussions with a physician should be scheduled to determine what course of treatment may be needed. Initial treatment for hypercholesterolemia usually requires dietary changes to reduce the intake of total fat, saturated fat, and cholesterol. Most health care professionals will recommend that a person's weight and height be proportionate. In addition to diet, guidelines recommend exercise to help bring weight and cholesterol to acceptable levels. Further, experts counsel persons with elevated blood cholesterol levels to increase their intake of soluble fiber. Sources of soluble fiber include bran, foods containing whole grains and other sources of indigestible fiber such as lignin. Physicians also recommend that patients with high cholesterol stop smoking as part of first-line therapy for hypercholesterolemia.

The reason for treating elevated cholesterol is to reduce an individual's risk of complications. If a diet low in cholesterol and saturated fats doesn't significantly reduce a person's cholesterol level, medication may be required. For every 1 percent reduction in cholesterol level, the risk of heart disease is reduced by 2 percent. It also is possible to partially reverse atherosclerosis that has already occurred by aggressively lowering cholesterol levels with diet and medications.

Prescription drugs are available to help lower cholesterol levels in the blood. These may be used as first-line therapy in high-risk patients or after about three months of dietary and lifestyle therapy. Cholestyramine, cholestipol, lovastatin, simvastatin, pravastatin, fluvaststin, rosuvastatin, and gemfibrazol are some of the drugs approved for use in the United States. The most often prescribed group of drugs are the statins, which also have been shown in some studies to reduce risk of depression and dementia.

There are advocates of treatment using vitamins, minerals and antioxidant substances in relatively high amounts. These amounts generally exceed those provided by the Food and Drug Administration in its Minimum Daily Requirements (MDR). Advocates of such therapies also emphasize increased levels of exercise, attaining an ideal body weight and increasing levels of fiber in one's diet.

Some people have advocated the use of garlic, soy and isoflavones to lower serum cholesterol levels. In 2003, enriched green tea was found to be an effective addition to a low-fat diet for lowering LDL cholesterol in adults.

The prognos is in direct proportion to serum cholesterol levels. People with hypercholesterolemia are at high risk of dying from heart disease.

Many studies have looked at the relationship between elevated cholesterol levels, increased risk for heart attack and death. In one investigation of relatively young males who had no known heart disease, cholesterol levels were measured and participants were followed for six years. During this time, all heart attacks and deaths that occurred among participants were recorded. As serum cholesterol levels increased, so did the risk of experiencing a fatal heart attack. The risk of a fatal heart attack was approximately five times higher among persons having cholesterol levels of 300 mg/dL or more compared to those with cholesterol levels below 200 mg/dL.

The Framingham Heart Study is an ongoing research effort. Cholesterol levels, smoking habits, heart attack rates, and deaths in the population of an entire town have been recorded for over 40 years. After 30 years, more than 85% of persons with cholesterol levels of 180 mg/dL or less were still alive; almost a third of those with cholesterol levels greater than 260 mg/dL had died.

Experts suggest the following steps to maintain serum cholesterol within normal limits: an important component is to maintain a normal weight for height and to reduce one's weight if it is inappropriate for height. Changing dietary habits by reducing the amount of fat and cholesterol consumed is advised. Doctors recommend avoiding smoking by not starting or quitting if currently a smoker. Increasing levels of fiber in the diet by including foods such as beans, raw fruits, whole grains and vegetables is receommended. It is important to exercise on a regular basis. Aerobic exercise is especially helpful in reducing serum cholesterol levels.

People from families with a strong history of early heart attacks should be evaluated with a lipid screen. Proper diet, exercise and the use of effective drugs can reduce serum lipid levels.

Nutrition and cardiac experts offer the following suggestions:

• purchasing low-fat or fat-free dairy products such as milk, cheese, sour cream, and yogurt
• eating lean red meats, chicken without skin, and fish
• reducing consumption of foods high in saturated fat such as french fries
• avoid foods that are rich sources of cholesterol such as eggs, liver, cheese, and bacon
• eating smaller servings
• keeping a food journal and writing down everything eaten each day
• prepare food by microwaving, boiling, broiling, or baking food instead of frying
• trimming the fat from meat before cooking it.