Polyunsaturated fats come from plants and fish. They are usually liquid at room temperature. Because of their high degree of unsaturation they break down rapidly and are more likely to combine with oxygen to form free radicals, which can damage tissues, ultimately placing you at higher rick for diseases such as arthritis, cataracts, and cancer. It seems from current research that the move away from saturated and polyunsaturated fats to monounsaturated fats is a healthy choice. Monounsaturated fats tend to raise the level of good cholesterol in the blood.
Cholesterol is found in every cell in the body and is an essential component of cell membranes.
Fat does not contain cholesterol, but many fatty foods do. However, cholesterol can be found even in low-fat foods like shrimp. Contrary to logic, dietary cholesterol does not have has much effect on blood cholesterol levels as saturated fat does. Blood cholesterol travels around in your bloodstream, going from the liver to the cells where it is needed. Because it can't travel around on its own, it hitches a ride on a vehicle called a lipoprotein.