Cholesterol is a type of fat, one which is very important for life. It is a vital building block of many substances including the cell membrane of every cell in our body. The word 'cholesterol' is associated with heart disease and obesity. However cholesterol is a very important type of fat for vital living. We have to have some cholesterol, but the liver can make as much as we need. If the level is too high, it can be deposited in tissues, specifically the arteries, causing them to narrow and not carry enough blood to vital organs such as the brain or the heart. It can also weaken the artery, causing it to enlarge and produce an aneurysm. This process is termed "arteriosclerosis".

The cholesterol in a person's blood originates from two major sources, dietary intake and liver production. Dietary cholesterol comes mainly from meat, poultry, fish, and dairy products. Organ meats, such as liver, are especially high in cholesterol content, while foods of plant origin contain no cholesterol. After a meal, cholesterol is absorbed by the intestines into the blood circulation and is then packaged inside a protein coat. This cholesterol-protein coat complex is called a chylomicron.