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INTRODUCTION: Cholesterol is a lipid (A greasy organic compound that is not soluble in water.) found in the cell membranes of all tissues, and is carried in the blood plasma of all animals. It is also considered a sterol (a combination steroid and alcohol) and is more abundant in tissues which either synthesize more of it or have more abundant densely-packed membranes, for example, the liver, spinal cord and brain and is NOT soluble in blood, but is transported in the circulatory system bound to one of the varieties of lipoproteins. Cholesterol is needed in the membranes of mammalian cells for normal cell function, and is either synthesized or derived from the diet, in which case it is carried by the bloodstream in low-density lipoproteins.

It is minimally soluble in water; it cannot dissolve and travel in the water-based bloodstream. It is primarily found in animal fats: all food containing animal fats contains cholesterol; food that does not contain animal fats either contains none or negligible amounts. It's a waxy, fat-like substance that can build up on the walls of your arteries (blood vessels that transport blood from the heart to other areas of the body) and plays an essential part in the formation of cell membranes, some hormones, and vitamin D.

DISEASE: Large quantities of low density particles (LDL) are strongly associated with the presence of arterial disease within the arteries. In contrast, having minimum amounts of large particles (HDL) has been independently associated with arterial disease progression within the arteries. In other words too much LDL or too little HDL is associated with arterial disease. This disease process can lead to a heart attack, stroke and peripheral vascular disease.

It is suggested that you have your cholesterol levels tested more frequently than five years if a person: has total levels of 200 mg/dL or greater, is a man over age 45 or a woman over age 50, has HDL (good) cholesterol less than 40 mg/dL, or other risk factors for heart disease and stroke. A campaign is under way to teach women that heart disease isn't for men only.

It's estimated that 70-million americans have at least one form of heart disease. New results from the Women's Health Initiative Dietary Modification Trial showed that eating a low-fat diet for 8 years DID NOT prevent heart disease, breast cancer, or colon cancer, and didn't do much for weight loss, either.

What is becoming clearer and clearer is that bad fats, meaning saturated and trans fats, increase the risk for certain diseases while good fats, meaning mono-unsaturated and poly-unsaturated fats, lower the risk. In a study of over 80,000 female nurses, Harvard researchers actually found that increasing cholesterol intake by 200 mg for every 1000 calories in the diet (about an egg a day) DID NOT appreciably increase the risk for heart disease. Recent research by Harvard investigators has shown that moderate egg consumption--up to one a day--DOES NOT increase heart disease risk in healthy individuals. People with diabetes, though, should probably limit themselves to no more than two or three eggs a week, as the Nurse's Health Study found that for such individuals, an egg a day might increase the risk for heart disease.

LEVELS: According to the lipid hypothesis, unusually high cholesterol levels (AKA hypercholesterolemia) and abnormal proportions of LDL and HDL are associated with cardiovascular disease by promoting atheroma development in arteries (atherosclerosis). Since elevated LDL contributes to this process, it is termed "bad cholesterol", while high levels of HDL ("good cholesterol") offer a degree of protection against heart disease. Abnormally low levels are termed hypocholesterolemia. As has been mention, high levels of cholesterol in the blood can raise your risk of heart disease and your levels tend to grow as you get older. In the 1960s and 70s, scientists established a link between high blood levels and heart disease.

Some kinds of fat are clearly good for cholesterol levels while others are clearly bad for them. While it is well known that high blood levels are associated with an increased chance for heart disease, scientific studies have indicated that there is only a weak relationship between the amount of cholesterol a person "consumes" and their blood cholesterol levels or risk for heart disease.

For some people with elevated levels, reducing the quantity in the diet has a small but helpful impact on blood cholesterol levels. While it's true that egg yolks have a lot of cholesterol--and, therefore may slightly affect blood levels--eggs also contain nutrients that may help reduce the risk for heart disease, including protein, vitamins B12 and D, riboflavin, and folate. Saturated fats increase total blood levels more than dietary cholesterol because they tend to boost both good HDL and bad LDL. Trans fats are even worse than saturated fats because they increase bad LDL and decrease good HDL.

In studies in which poly-unsaturated and mono-unsaturated fats were consumed in place of carbohydrates, these good fats lowered LDL levels and raised HDL levels. Logically, most of the influence that fat intake has on heart disease is due to its effect on blood cholesterol levels. In other words, low-fat diets appear to offer no obvious advantages over diets with fat levels close to the national average.

CONCLUSION: Cholesterol is a waxy, fat-like substance that is found in every cell of the body and is also found in some of the foods you eat. It is recommended by the American Heart Association to test cholesterol levels every five years for people aged 20 years or older. There are often no signs or symptoms that you have high blood cholesterol, but it can be detected with a blood test. You are likely to have elevated levels if members of your family have it, if you are overweight or if you eat a lot of fatty foods. You can decrease your cholesterol by exercising more and consuming more fruits and vegetables. You also may need to take medicine to lower it.