There are two major sources of cholesterol: diet and liver. Around 75% of blood cholesterol is produced by the liver while the remaining 25% is contributed by the foods we consume. The dietary sources include animal products such as dairy products, fish, meat, and poultry. The liver takes dietary lipids from the bloodstream and produces cholesterol. Since the cholesterol is insoluble in blood, the liver packs it along with special proteins into tiny sphere-like structures called lipoproteins. The bloodstream carries these lipoproteins to all the cells of the body, which extract the required amount of cholesterol from them. The lipoproteins are classified as LDL (low density lipoproteins) which is also referred as bad cholesterol, and HDL (high density lipoproteins) also known as good cholesterol. If dietary lipids are not available, the liver produces cholesterol on its own.
The liver produces about 1,000 mg of cholesterol everyday. From that, approximately 800 mg is used for the production of bile salts and the rest is used for other functions. The desirable level of total blood cholesterol is less than 200 mg/dL. If the level is more than 240 mg/dL, then the condition is known as hypercholesterolemia. The desirable level of HDL cholesterol is 40-50 mg/dL and less than 100 mg/dL for LDL cholesterol.
The excess amounts of LDL cholesterol get deposited inside the arteries, which gives rise to a condition called arteriosclerosis. A restricted blood flow can lead to blockage of arteries, and it may result in a stroke or heart disease. The HDL cholesterol helps prevent the clogging of arteries. Hence, higher the HDL level, lower is the risk of heart diseases. Therefore, a healthy lifestyle is essential to maintain a good balance between these two cholesterol levels and prevent any heart disorders.