Water and oils do not mix. In order for lipids to travel in the blood they must be coated with protein to create a water-soluble package. Cholesterol is part of the structure of all lipoproteins. By measuring lipoproteins in the blood, excess cholesterol can be detected. Cholesterol is a fat-like substance with a waxy consistency that is produced in the livers of humans and other animals.
Every human cell needs a minute amount of cholesterol in order to function properly.
While some cholesterol is essential, too much can be harmful. Because it is waxy, cholesterol can stick to the interior of blood vessel walls. Over time, cholesterol, fat and other substances can accumulate and narrow blood vessels. This is the initial stage of atherosclerosis. The fats transported in the blood are called triglycerides.