Cholesterol is a waxy fat like substance found in animal fats and oils.It is also produced by the human body,largely in the liver and to a small extend in the small intestines.Cholesterol is essential in the formation of cell walls.It is also required in the manufacture of hormones like Testosterone.

Cholesterol which is absorbed in the small intestines need to combine with a protein,apolipoprotein, before it can be transported(in liquid form) in the blood. Hence in blood it exists in the form of Low density lipoprotein(LDL) cholesterol and High density lipoprotein(HDL) cholesterol.
LDL Cholesterol
Cholesterol is taken to the various parts of our body by the blood vessels in LDL form.When in elevated levels,they are oxidised by the free radicals and tend to form plaques in the artery walls,leading to atherosclerosis and coronary artery disease.Hence it is also called BAD cholesterol!

Formation of plaque in the coronary artery wall.

HDL Cholesterol
HDL Cholesterol removes excess cholesterol in the blood and takes it to the liver where it is broken down and excreted.As it tends to clear the LDL cholesterol from the blood vessels and decreases the cardiac risks it is also referred to as GOOD cholesterol.

Blood cholesterol levels must be kept within the normal range to prevent coronary artery disease.The acceptable levels are:-

Total Cholesterol:- less than 200 mg/dl
LDL-Cholesterol:- less than 130 mg/dl
HDL- cholesterol:-more than 35mg/dl

Factors Affecting Cholesterol Level in Blood
Genetics
Some are born with hereditary defects -some produce excessive cholesterol in their livers.Others produce excess apolipoprotein in the body and tend to absorb cholesterol more than the others!

Thyroid Gland Disorder
Deminished thyroid gland functions or Hypothyroidism produces elevated cholesterol levels in the blood

Saturated Fatty Acids
Saturated fats raise blood cholesterol levels more than anything else.Foods rich in saturated fatty acids are beef fat,pork fat(lard),butter,whole milk,cheese,coconut oil,palm oil,palm kernal oil and cocoa butter.

Unsaturated Fatty Acids
Unsaturated fats decrease LDL cholesterol levels and increase the HDL chlosterol levels

Dietary Cholesterol Intake
Dietary cholesterol increase our blood cholesterol level but not as much as saturated fat

High Fibre Diet
Foods high in fibres like cereals.grains,fruits and vegetables decrease the absortion of dietary cholesterol

Smoking
Increases LDL cholesterol.QUIT SMOKING NOW!

Exercises
Exercises increase the HDL cholesterol level