Good afternoon. You've probably read news stories that characterize cholesterol negatively because of its association with heart disease. In this lecture, I'd like to explain why this view is overly simplistic. Cholesterol is a type of fat found naturally in all of our blood and tissue cells. The body uses this wax like substance to maintain and repair itself on a daily basis. For example, cholesterol contributes to the formation of cell membranes and to the production of bile, which helps the body to digest fat. It also produces hormones such as estrogen and testosterone. And converts energy from sunlight into Vitamin D. So, cholesterol has essential health functions. It only becomes a health risk when its concentration in the blood is too high. This happens because although cholesterol is created by our livers, it is also present in many of the animal derived foods we eat. Red meat, eggs and dairy products. Contain especially high amounts when cholesterol levels are elevated, deposits can build up on the walls of the arteries, which restrict blood flow and can eventually lead to heart attacks and stroke. It is also possible. However, for cholesterol levels to be low, although the condition is not common, recent studies have linked insufficient cholesterol to anxiety, depression and some types of cancer.