Most cholesterol is not dietary in origin, it is synthesized internally. Only about 20% of cholesterol comes directly from the diet - the other 80% is produced by the liver.
Cholesterol is a lipid (a type of fat) which is transported in blood plasma and found in the cell membranes of all body tissues. It is excreted from the liver and bile and is reabsorbed from the intestines.
Cholesterol is commonly mistaken as a bad thing. However, cholesterol is needed to build and maintain cells and is essential in many biochemical processes. It aids in the manufacture of bile, is important for the metabolism of fat soluble vitamins (A, D, E, and K), is a major precursor for the synthesis of vitamin D and of various steroid hormones (cortisol, aldosteron, progesterone, oestrogen and testosterone).
There are 2 types of cholesterol...'bad cholesterol', or low-density lipoprotein (LDL), and ‘good cholesterol', or high-density lipoprotein (HDL). Problem occur when these 2 levels get out of balance.
LDLs attach to the walls of the arteries and create ‘plaque', which accumulates over time to cause the arteries to narrow, resulting in heart attacks and strokes. About 70% of cholesterol is transported as LDL, which is mostly fat.
HDLs travel in the blood picking up LDLs ready for excretion. About 20% of cholesterol is transported as HDL, which is mostly protein.
Triglycerides are a different type of fat associated with cholesterol. They are stored in fat tissue, or are carried in the blood as very low-density lipoproteins (VLDL).
The main risk associated with high cholesterol is an excess of LDL cholesterol, leading to coronary heart disease (CHD). A raised level of blood triglycerides together with high LDL increases the risk of heart disease.
Causes
There are several factors that contribute to high blood cholesterol levels: