Cholesterol — a soft, waxy substance — is one of the lipids found in the blood and, indeed, in all the cells of the body. Important to the healthy functioning of our bodies, cholesterol is a part of our cells' membranes and is used in the production of hormones. [ad:media]The cholesterol in the human body may originate from foods rich in cholesterol — such as meat, eggs and diary products — or it can be made internally by our bodies. The body can also produce cholesterol from foods that do not themselves contain cholesterol but that do contain saturated fat — such as palm oil and coconut oil — or from trans fats — such as fried food in restaurants and commercial cakes or cookies. Cholesterol by itself does not dissolve in blood; it has to be combined with proteins to form soluble lipoprotein particles. Lipoproteins come in two forms: low-density lipoprotein (LDL) and high-density lipoprotein (HDL). LDL is considered "bad cholesterol" because too much of it leads to a narrowing and stiffening of the arteries due to a buildup of cholesterol, which accumulate in deposits called "plaques" on the arteries' inner walls. This condition is called atherosclerosis. It contributes to hypertension and causes peripheral artery disease, coronary artery disease, heart attack and stroke — as well as erectile dysfunction in men. In contrast, HDL cholesterol is considered "good cholesterol" because it reduces the risk of cardiovascular disease by transporting cholesterol away from the bloodstream and back to the liver, which facilitates its removal from the body. HDL thus helps to prevent the buildup of cholesterol plaques on the walls of the arteries. An individual's HDL cholesterol level is to some extent a factor of one's genetic makeup. But HDL levels can be lowered by type 2 diabetes; certain drugs, such as beta blockers and anabolic steroids; smoking; being overweight; and being sedentary. On the other hand, estrogen, a female hormone, raises HDL levels, partially explaining why cardiovascular disease is less prevalent in premenopausal women. Triglycerides are another factor in hyperlipidemia. Triglyceride is the most common type of fat in the body. Normal triglyceride levels vary by age and sex. High triglyceride levels combined with high levels of LDL cholesterol increase one's risk of cardiovascular disease. Your cholesterol level is a composite measure of all these lipids, in either milligrams per deciliter of blood (mg/dL) or millimoles per liter of blood (mmol/L). \n*Many American experts recommend the following cholesterol levels:* - Total cholesterol: 200 mg/dL (5.2 mmol/L) - LDL cholesterol: from below 70 mg/dL (1.8 mmol/L) to 129 mg/dL (3.3 mmol/L), depending on your health status - HDL cholesterol: above 60 mg/dL (1.6 mmol/L) - Triglycerides: below 150 mg/dL (3.9 mmol/L) Source: American Heart Association The American Heart Association recommends that all adults age 20 and older have their cholesterol and other risk factors for hyperlipidemia checked every four to six years and also work with their health-care providers to determine their risk for cardiovascular disease and stroke.