Cholesterol is a fatty substance called a lipid that is important to aid the normal functionality of the body. Cholesterol is produced mainly by the liver but can also be found in foods. Cholesterol is carried in your blood by proteins which when combined are called lipoproteins. There are two types of lipoproteins, the 'good' protective high-density lipoprotein (HDL) and the 'bad' harmful low-density lipoprotein (LDL). Cholesterol can increase the risk of atherosclerosis, heart attack, stroke and TIA.