a complex fatty alcohol, is essential for the proper working of the digestive and nervous systems. It is present in foods of animal origin, large amounts being found in egg yolk. Cholesterol is insoluble in water. In the body of a man or an animal; it is carried around by two types of proteins, low density lipoproteins (LDL) and high density lipoproteins (HDL). LDL is notorious as a contributory cause of atherosclerosis—clogging of the arteries with fatty deposits of pure cholesterol as well as gallstones. HDL, in contrast, is wholly beneficial and helps to keep the arteries clear. But it should be noted that some LDL is necessary; it is only harmful in excess.
In Harvard during the 1950s, Konrad Bloch and Feodor Lynen worked out the role of cholesterol in the body and its link with atherosclerosis, for which they won a Nobel prize in 1964. Most of the cholesterol in humans is produced internally, in liver; it is carried in the body by LDL and HDL. It became clear that many people in western countries had dangerously high levels of LDL and that this was caused, at least partly, by eating fatty foods. In particular, there were worries about foods which were themselves high in cholesterol, and some people stopped eating eggs altogether.
It is now thought that the main cause of high LDL levels is not eating cholesterol itself, but a combination of too much saturated fat (see fats and oils) in the diet, and lack of exercise.
Ralph Hancock is an encyclopedist with a special interest in food history and food science.
