Cholesterol. Produced by almost all cells in the body, but particularly by the liver and the intestine, cholesterol is an important constituent of cell membranes, the protective outer coat of the cell. It's also needed for the production of numerous hormones, including the sex hormones, and is indirectly involved in digestion, since it's required for the production of bile.

LDL, HDL and VLDL. These are complexes of fat and protein, which transport cholesterol through the blood and deposit it at various cells throughout the body. LDL is the most common and stands for low-density lipoprotein. HDL, high-density lipoprotein, is considered protective since it helps remove cholesterol from the body. HDL levels rise with exercise. VLDL, present in the lowest quantities, stands for very-low-density lipoprotein.

Dietary cholesterol. The cholesterol present in food is now considered harmful if too much is consumed. Evidence suggests that eating too much cholesterol and saturated fat raises blood cholesterol levels, which causes cells to accumulate cholesterol. The result: Excess cholesterol is deposited in cells lining blood vessel. This leads to atherosclerosis -- hardening of the arteries.

Saturated fats. Consumption of these fats, found predominately meat and dairy foods, raises blood cholesterol levels. The term saturated refers to chemical bonds. Saturated fats contain more hydrogen atoms than other types of fat.

Polyunsaturated fats. Fat derived from vegetable and plant sources such as soybean, corn and safflower oil. Polyunsaturated fat helps clear saturated fat from the body. It contains the least amount of hydrogen.

Monounsaturated fats. Also derived from plant and vegetable sources, the best-known examples are olive and peanut oils. This type of fat does not appear to raise total blood cholesterol levels, although it may increase levels of HDL, the "good" lipoprotein. The hydrogen levels of monounsaturated fats fall between those of saturated and polyunsaturated fats.