The central idea behind most medical advice concerning diet is that good health requires a low level of fats and cholesterol in the blood. Research studies have shown repeatedly that people with high cholesterol levels are most likely to suffer heart attacks, strokes, and other diseases of the blood vessels.

The link with heart disease is easy to understand. The underlying cause of most heart attacks and strokes is atherosclerosis, a narrowing of the blood vessels caused by deposits if a yellow, greasy substance called atheroma on the inside lining of the arteries. Atheroma (from the Greek word for porridge) consists mainly of cholesterol, which is an essential part of the structure of cell walls. However, when there is too much cholesterol in the blood, it accumulates in the walls of blood vessels, narrowing them and increasing the vital blood flow to the heart and brain.