Cholesterol is a waxy substance found in the body's cells; it is similar to fat. The body makes cholesterol, but it also appears in some foods. High levels of cholesterol in the blood create an increased risk of heart disease, since cholesterol is a component of the plaque that can build up inside artery walls and eventually cause them to become blocked.
Cholesterol only appears in foods from animal sources, such as meat, poultry and full-fat dairy products. Diets high in saturated and trans fats cause the liver to produce more cholesterol.
Cholesterol travels through the body via two different types of lipoproteins. High levels of low-density lipoproteins, also known as LDL or "bad" cholesterol, lead to an increased risk of heart disease. The other type of lipoproteins are known as high-density lipoproteins, HDL or "good" cholesterol. The higher a person's HDL levels, the lower his risk of developing heart disease.
A person is considered to have high blood cholesterol if his total blood cholesterol level is 240 milligrams per deciliter or greater. A blood cholesterol level between 200 and 239 milligrams per deciliter is considered borderline high, and a level less than 200 milligrams per deciliter is considered ideal.