Cholesterol is a fatty substance essential for normal body functioning, as it contributes to the synthesis of some hormones and vitamin D and is a component of cell membranes. Cholesterol is produced in the liver, but can also be introduced through diet by consuming food high in animal fats, such as meat, butter, cured meats, cheese, egg yolk and liver. It is not found in fruit, vegetables and cereals.
A specific class of particles, known as lipoproteins, are responsible for carrying cholesterol through the blood. Lipoproteins are classified into four groups, based on their density, which is inversely proportional to the amount of cholesterol present. The most important ones for the purpose of cardiovascular prevention are:
- Low-density lipoproteins, or LDL, which carry newly synthesized cholesterol from the liver to body cells
- High-density lipoproteins, or HDL, which collect excess cholesterol from tissues and transport it back to the liver for excretion.