What is Cholesterol?

By Dr Ananya Mandal, MD

Cholesterol is a fatty substance that is waxy and exists as small molecules within the human body. It is found in all cells of the body.

What does cholesterol do?

Cholesterol is an essential component that makes hormones, bile acids, vitamin D, and substances that help in the digestion of food.

The cholesterols in the body are also important for cell structures, nerves, brain, liver and other organs as well.

Where is cholesterol found?

The body is able to synthesize all the cholesterol it needs. The liver produces about 1,000 milligrams of cholesterol a day and this can meet the needs of the body. Cholesterol is also found in the foods that one consumes.

Lipoproteins

Cholesterol exists as small molecules in blood and is carried in packages called lipoproteins. Cholesterol cannot dissolve in the blood and has to be transported to and from the cells by lipoproteins.

The lipoproteins have two components – “lipids” or fatty component and “protein” component. The lipids lie within the core of the molecule while the proteins lie outside.

Types of lipoprotein

Two kinds of lipoproteins carry cholesterol in blood. These are - low-density lipoproteins (LDL) and high-density lipoproteins (HDL). To be healthy both LDL and HDL levels need to be normal.

Bad and good cholesterol

LDL cholesterol sometimes is called “bad” cholesterol. A high level of LDL cholesterol in the arteries can lead to a build-up within the walls leading to narrowing and blockages. This is called atherosclerosis.

In vital arteries of the heart (coronary arteries), brain and other organs, atherosclerosis can cause major life-threatening problems. Some of these include angina, heart attacks and strokes.

On the other hand HDL cholesterol is called “good” cholesterol. This is because it carries cholesterol from other parts of the body and brings them back to the liver for breakdown and removal or for reuse.

Another form of bad cholesterol is Triglycerides. A triglyceride is a form of fat made in the body. These also cause a build-up within the arteries. High triglycerides are caused due to overweight/obesity, physical inactivity, excess alcohol consumption, cigarette smoking, and a diet very high in refined carbohydrates.

Lp(a) Cholesterol is a genetic variation of LDL (bad) cholesterol. A high level of Lp(a) is a significant for development of atherosclerosis.

The greatest danger is when a person has high levels of LDL cholesterol and trigylcerides, and low levels of HDL cholesterol.

Cholesterol in food

Food does not contain cholesterol per se. There is very little cholesterol in foods. The main culprits are eggs, offal and shellfish. However, foods that are rich is saturated fats are dangerous because when ingested the liver turns this fat into cholesterol.
Reviewed by , BA Hons (Cantab)

Further Reading

Last Updated: Oct 8, 2014

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